| 1 | <html> |
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| 2 | <head> |
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| 3 | <title>The Particle Data Scheme</title> |
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| 4 | <link rel="stylesheet" type="text/css" href="pythia.css"/> |
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| 5 | <link rel="shortcut icon" href="pythia32.gif"/> |
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| 6 | </head> |
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| 7 | <body> |
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| 8 | |
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| 9 | <h2>The Particle Data Scheme</h2> |
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| 10 | |
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| 11 | The particle data scheme may take somewhat longer to understand than |
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| 12 | the settings one. In particular the set of methods to access information |
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| 13 | is rather more varied, to allow better functionality for advanced usage. |
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| 14 | However, PYTHIA does come with a sensible default set of particle |
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| 15 | properties and decay tables. Thus there is no need to learn any of the |
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| 16 | methods on this page to get going. Only when you perceive a specific need |
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| 17 | does it make sense to learn the basics. |
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| 18 | |
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| 19 | <p/> |
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| 20 | The central section on this page is the Operation one. The preceding |
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| 21 | sections are there mainly to introduce the basic structure and the set |
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| 22 | of properties that can be accessed. The subsequent sections provide a |
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| 23 | complete listing of the existing public methods, which most users |
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| 24 | probably will have little interaction with. |
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| 25 | |
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| 26 | <h3>Databases</h3> |
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| 27 | |
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| 28 | The management of particle data is based on three classes: |
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| 29 | <ul> |
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| 30 | <li><code>ParticleData</code>, which is the top-level class, with |
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| 31 | methods that can be used to interrogate all particle data. It contains |
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| 32 | a map of PDG particle identity numbers [<a href="Bibliography.html" target="page">Yao06</a>] onto the relevant |
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| 33 | <code>ParticleDataEntry</code> objects,</li> |
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| 34 | <li><code>ParticleDataEntry</code>, which stores the relevant information |
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| 35 | on an individual particle species, and</li> |
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| 36 | <li><code>DecayChannel</code>, which stores info on one particular decay |
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| 37 | mode of a particle.</li> |
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| 38 | |
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| 39 | </ul> |
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| 40 | The objects of these classes together form a database that is |
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| 41 | continuously being used as the program has to assign particle masses, |
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| 42 | select decay modes, etc. |
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| 43 | |
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| 44 | <p/> |
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| 45 | Each <code>Pythia</code> object has a public member |
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| 46 | <code>particleData</code> of the <code>ParticleData</code> class. |
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| 47 | Therefore you access the particle data methods as |
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| 48 | <code>pythia.particleData.command(argument)</code>, |
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| 49 | assuming that <code>pythia</code> is an instance of the |
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| 50 | <code>Pythia</code> class. Further, for some of the most frequent user |
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| 51 | tasks, <code>Pythia</code> methods have been defined, so that |
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| 52 | <code>pythia.command(argument)</code> |
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| 53 | would work, see further below. |
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| 54 | |
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| 55 | <p/> |
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| 56 | A fundamental difference between the particle data classes and the |
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| 57 | settings ones is that the former are accessed regularly during the |
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| 58 | event generation process, as a new particle is produced and its mass |
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| 59 | need to be set, e.g., while the latter are mainly/only used |
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| 60 | at the initialization stage. Nevertheless, it is not a good idea to |
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| 61 | change data in either of them in mid-run, since this may lead to |
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| 62 | inconsistencies. |
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| 63 | |
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| 64 | <h3>Stored properties for particles</h3> |
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| 65 | |
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| 66 | The main properties stored for each particle are as follows. |
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| 67 | Different ways to set and get these properties will be described |
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| 68 | further down. |
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| 69 | |
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| 70 | <ul> |
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| 71 | |
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| 72 | <li><code>name</code>: a character string with the name of the |
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| 73 | particle. Particle and antiparticle names are stored separately, |
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| 74 | with <code>void</code> returned when no antiparticle exists.</li> |
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| 75 | |
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| 76 | <li><code>spinType</code>: the spin type, of the form <i>2 s + 1</i>, |
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| 77 | with special code 0 for entries of unknown or indeterminate spin.</li> |
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| 78 | |
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| 79 | <li><code>chargeType</code>: three times the charge (to make it an |
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| 80 | integer).</li> |
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| 81 | |
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| 82 | <li><code>colType</code>: the colour type, with 0 uncoloured, 1 triplet, |
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| 83 | -1 antitriplet and 2 octet. (A preliminary implementation of colour |
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| 84 | sextets, available since version 8.150, further uses 3 for a sextet |
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| 85 | and -3 for an antisextet.) </li> |
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| 86 | |
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| 87 | <li><code>m0</code>: the nominal mass <i>m_0</i> (in GeV).</li> |
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| 88 | |
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| 89 | <li><code>mWidth</code>: the width <i>Gamma</i> of the Breit-Wigner |
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| 90 | distribution (in GeV).</li> |
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| 91 | |
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| 92 | <li><code>mMin</code>: the lower limit of the allowed mass range |
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| 93 | generated by the Breit-Wigner (in GeV). Has no meaning for particles |
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| 94 | without width, and would typically be 0 there.</li> |
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| 95 | |
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| 96 | <li><code>mMax</code>: the upper limit of the allowed mass range |
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| 97 | generated by the Breit-Wigner (in GeV). If <i>mMax < mMin</i> then |
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| 98 | no upper limit is imposed. Has no meaning for particles without width, |
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| 99 | and would typically be 0 there.</li> |
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| 100 | |
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| 101 | <li><code>tau0</code>: the nominal proper lifetime <i>tau_0</i> |
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| 102 | (in mm/c).</li> |
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| 103 | |
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| 104 | <li><code>isResonance</code>: a flag telling whether a particle species |
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| 105 | is considered as a resonance or not. Here |
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| 106 | <a href="ResonanceDecays.html" target="page">"resonance"</a> is used as shorthand |
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| 107 | for any massive particle where the decay process should be counted as part |
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| 108 | of the hard process itself, and thus be performed before showers and other |
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| 109 | event aspects are added. Restrictions on allowed decay channels is also |
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| 110 | directly reflected in the cross section of simulated processes, while |
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| 111 | those of normal hadrons and other light particles are not. |
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| 112 | In practice, it is reserved for states above the <i>b bbar</i> |
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| 113 | bound systems in mass, i.e. for <i>W, Z, t</i>, Higgs states, |
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| 114 | supersymmetric states and (most?) other states in any new theory. |
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| 115 | All particles with <code>m0</code> above 20 GeV are by default |
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| 116 | initialized to be considered as resonances.</li> |
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| 117 | |
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| 118 | <li><code>mayDecay</code>: a flag telling whether a particle species |
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| 119 | may decay or not, offering the main user switch. Whether a given particle |
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| 120 | of this kind then actually will decay also depends on it having allowed |
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| 121 | decay channels, and on other flags for |
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| 122 | <a href="ParticleDecays.html" target="page">particle decays</a>. |
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| 123 | All particles with <code>tau0</code> below 1000 mm are |
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| 124 | by default initialized to allow decays.</li> |
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| 125 | |
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| 126 | <li><code>doExternalDecays</code>: a flag telling whether a particle |
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| 127 | should be handled by an external decay package or not, with the latter |
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| 128 | default. Can be manipulated as described on this page, but should |
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| 129 | normally not be. Instead the |
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| 130 | <code><a href="ExternalDecays.html" target="page">Pythia::decayPtr(...)</a></code> |
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| 131 | method should be provided with the list of relevant particles.</li> |
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| 132 | |
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| 133 | <li><code>isVisible</code>: a flag telling whether a particle species |
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| 134 | is to be considered as visible in a detector or not, as used e.g. in |
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| 135 | analysis routines. By default this includes neutrinos and a few BSM |
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| 136 | particles (gravitino, sneutrinos, neutralinos) that have neither strong |
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| 137 | nor electromagnetic charge, and are not made up of constituents that |
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| 138 | have it. The value of this flag is only relevant if a particle is |
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| 139 | long-lived enough actually to make it to a detector.</li> |
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| 140 | |
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| 141 | <li><code>doForceWidth</code>: a flag valid only for resonances where |
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| 142 | PYTHIA contains code to calculate the width of the resonance from |
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| 143 | encoded matrix-element expressions, i.e. the <i>Z^0</i>, <i>W^+-</i>, |
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| 144 | <i>t</i>, <i>h^0</i>, and a few more. The normal behaviour |
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| 145 | (<code>false</code>) is then that the width is calculated from the mass, |
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| 146 | but it is possible to <a href="ResonanceDecays.html" target="page">force</a> the |
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| 147 | resonance to retain the nominal width. Branching ratios and the running |
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| 148 | of the total width are unaffected.</li> |
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| 149 | |
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| 150 | </ul> |
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| 151 | |
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| 152 | <h3>Stored properties for decays</h3> |
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| 153 | |
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| 154 | An unstable particle has a decay table consisting of one or more |
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| 155 | decay channel. The following properties are stored for each such channel. |
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| 156 | Again different ways to set and get these properties will be described |
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| 157 | further down. |
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| 158 | <ul> |
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| 159 | |
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| 160 | <li><code>onMode</code>: integer code for use or not of channel,<br/> |
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| 161 | 0 if a channel is off,<br/> |
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| 162 | 1 if on,<br/> |
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| 163 | 2 if on for a particle but off for an antiparticle,<br/> |
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| 164 | 3 if on for an antiparticle but off for a particle.<br/> |
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| 165 | If a particle is its own antiparticle then 2 is on and 3 off |
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| 166 | but, of course, for such particles it is much simpler and safer |
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| 167 | to use only 1 and 0.<br/> |
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| 168 | The 2 and 3 options can be used e.g. to encode CP violation in |
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| 169 | B decays, or to let the <i>W</i>'s in a <i>q qbar -> W^+ W^-</i> |
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| 170 | process decay in different channels. </li> |
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| 171 | |
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| 172 | <li><code>bRatio</code>: the branching ratio of the channel.</li> |
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| 173 | |
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| 174 | <li><code>meMode</code>: the mode of processing this channel, possibly |
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| 175 | with matrix elements; see the |
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| 176 | <a href="ParticleDecays.html" target="page">particle decays</a> description</li> |
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| 177 | for the list of possibilities. |
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| 178 | |
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| 179 | <li><code>multiplicity</code>: the number of decay products of the |
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| 180 | channel. Can be at most 8.</li> |
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| 181 | |
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| 182 | <li><code>product(i)</code>: the identity code of the decay products, |
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| 183 | where <code>i</code> runs between <code>0</code> and |
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| 184 | <code>multiplicity - 1</code>. Trailing positions are filled with 0. |
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| 185 | </li> |
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| 186 | |
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| 187 | </ul> |
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| 188 | |
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| 189 | <h3>Operation</h3> |
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| 190 | |
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| 191 | The normal flow of the particle data operations is: |
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| 192 | |
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| 193 | <ol> |
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| 194 | |
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| 195 | <li> |
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| 196 | When a <code>Pythia</code> object <code>pythia</code> is created, the |
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| 197 | <code>pythia.particleData</code> member is asked to scan the |
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| 198 | <code>ParticleData.xml</code> file. |
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| 199 | |
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| 200 | <p/> |
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| 201 | All lines beginning with <code><particle</code> are scanned for |
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| 202 | information on a particle species, and all lines beginning with |
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| 203 | <code><channel</code> are assumed to contain a decay channel of the |
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| 204 | enclosing particle. In both cases XML syntax is used, with attributes |
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| 205 | used to identify the stored properties, and with omitted properties |
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| 206 | defaulting back to 0 where meaningful. The particle and channel |
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| 207 | information may be split over several lines, up to the > endtoken. |
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| 208 | The format of a <code><particle</code> tag is: |
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| 209 | <pre> |
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| 210 | <particle id="..." name="..." antiName="..." spinType="..." chargeType="..." colType="..." |
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| 211 | m0="..." mWidth="..." mMin="..." mMax="..." tau0="..."> |
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| 212 | </particle> |
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| 213 | </pre> |
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| 214 | where the fields are the properties already introduced above. |
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| 215 | Note that <code>isResonance</code>, <code>mayDecay</code>, |
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| 216 | <code>doExternalDecay</code>, <code>isVisible</code> and |
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| 217 | <code>doForceWidth</code> are not set here, but are provided with |
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| 218 | default values by the rules described above. Once initialized, also |
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| 219 | these latter properties can be changed, see below.<br/> |
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| 220 | |
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| 221 | The format of a <code><channel></code> tag is: |
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| 222 | <pre> |
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| 223 | <channel onMode="..." bRatio="..." meMode="..." products="..." /> |
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| 224 | </pre> |
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| 225 | again see properties above. The products are given as a blank-separated |
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| 226 | list of <code>id</code> codes. |
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| 227 | <br/><b>Important</b>: the values in the <code>.xml</code> file should not |
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| 228 | be changed, except by the PYTHIA authors. Any changes should be done |
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| 229 | with the help of the methods described below. |
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| 230 | </li> |
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| 231 | |
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| 232 | <li> <p/> |
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| 233 | Between the creation of the <code>Pythia</code> object and the |
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| 234 | <code>init</code> call for it, you may use the methods of the |
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| 235 | <code>ParticleData</code> class to modify some of the default values. |
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| 236 | Several different approaches can be chosen for this. |
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| 237 | |
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| 238 | <p/> |
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| 239 | a) Inside your main program you can directly set values with |
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| 240 | <pre> |
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| 241 | pythia.readString(string); |
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| 242 | </pre> |
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| 243 | where both the variable name and the value are contained inside |
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| 244 | the character string, separated by blanks and/or a =, e.g. |
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| 245 | <pre> |
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| 246 | pythia.readString("111:mayDecay = off"); |
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| 247 | </pre> |
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| 248 | switches off the decays of the <i>pi^0</i>.<br/> |
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| 249 | |
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| 250 | The particle id (> 0) and the property to be changed must be given, |
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| 251 | separated by a colon.<br/> |
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| 252 | |
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| 253 | The allowed properties are: <code>name</code>, <code>antiName</code>, |
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| 254 | <code>spinType</code>, <code>chargeType</code>, <code>colType</code>, |
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| 255 | <code>m0</code>, <code>mWidth</code>, <code>mMin</code>, |
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| 256 | <code>mMax</code>, <code>tau0</code>, <code>isResonance</code>, |
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| 257 | <code>mayDecay</code>, <code>doExternalDecay</code>, |
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| 258 | <code>isVisible</code> and <code>doForceWidth</code>. All of these |
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| 259 | names are case-insensitive. Names that do not match an existing |
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| 260 | variable are ignored.<br/> |
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| 261 | |
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| 262 | Strings beginning with a non-alphanumeric character, like # or !, |
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| 263 | are assumed to be comments and are not processed at all. For |
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| 264 | <code>bool</code> values, the following notation may be used |
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| 265 | interchangeably: <code>true = on = yes = ok = 1</code>, while everything |
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| 266 | else gives <code>false</code> (including but not limited to |
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| 267 | <code>false</code>, <code>off</code>, <code>no</code> and |
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| 268 | <code>0</code>). |
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| 269 | |
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| 270 | <p/> |
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| 271 | Particle data often comes in sets of closely related information. |
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| 272 | Therefore some properties expect the value to consist of several |
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| 273 | numbers. These can then be separated by blanks (or by commas). |
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| 274 | A simple example is <code>names</code>, which expects both the |
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| 275 | name and antiname to be given. A more interesting one is the |
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| 276 | <code>all</code> property, |
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| 277 | <pre> |
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| 278 | id:all = name antiName spinType chargeType colType m0 mWidth mMin mMax tau0 |
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| 279 | </pre> |
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| 280 | where all the current information on the particle itself is replaced, |
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| 281 | but any decay channels are kept unchanged. Using <code>new</code> instead |
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| 282 | of <code>all</code> also removes any previous decay channels. |
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| 283 | If the string contains fewer fields than expected the trailing |
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| 284 | properties are set to vanish ("void", 0 or 0.). Note that such a |
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| 285 | truncated string should not be followed by a comment, since this |
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| 286 | comment would then be read in as if it contained the missing properties. |
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| 287 | The truncation can be done anywhere, specifically a string with only |
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| 288 | <code>id:new</code> defines a new "empty" particle. |
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| 289 | As before, <code>isResonance</code>, <code>mayDecay</code>, |
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| 290 | <code>doExternalDecay</code>, <code>isVisible</code> and |
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| 291 | <code>doForceWidth</code> are (re)set to their default values, and |
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| 292 | would have to be changed separately if required. |
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| 293 | |
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| 294 | <p/> |
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| 295 | A further command is <code>rescaleBR</code>, which rescales each of the |
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| 296 | existing branching ratios with a common factor, such that their new |
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| 297 | sum is the provided value. This may be a first step towards adding |
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| 298 | new decay channels, see further below. |
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| 299 | |
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| 300 | <p/> |
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| 301 | Alternatively the <code>id</code> code may be followed by another integer, |
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| 302 | which then gives the decay channel number. This then has to be |
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| 303 | followed by the property specific to this channel, either |
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| 304 | <code>onMode</code>, <code>bRatio</code>, <code>meMode</code> or |
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| 305 | <code>products</code>. In the latter case all the products of |
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| 306 | the channel should be given: |
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| 307 | <pre> |
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| 308 | id:channel:products = product1 product2 .... |
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| 309 | </pre> |
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| 310 | The line will be scanned until the end of the line, or until a |
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| 311 | non-number word is encountered, or until the maximum allowed number |
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| 312 | of eight products is encountered, whichever happens first. (Thus the |
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| 313 | multiplicity of a decay channel need not be input; it is automatically |
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| 314 | calculated from the products list.) It is also possible to replace all |
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| 315 | the properties of a channel in a similar way: |
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| 316 | <pre> |
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| 317 | id:channel:all = onMode bRatio meMode product1 product2 .... |
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| 318 | </pre> |
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| 319 | To add a new channel at the end, use |
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| 320 | <pre> |
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| 321 | id:addChannel = onMode bRatio meMode product1 product2 .... |
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| 322 | </pre> |
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| 323 | |
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| 324 | <p/> |
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| 325 | It is currently not possible to remove a channel selectively, but |
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| 326 | setting its branching ratio vanishing is as effective. If you want to |
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| 327 | remove all existing channels and force decays into one new channel |
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| 328 | you can use |
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| 329 | <pre> |
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| 330 | id:oneChannel = onMode bRatio meMode product1 product2 .... |
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| 331 | </pre> |
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| 332 | A first <code>oneChannel</code> command could be followed by |
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| 333 | several subsequent <code>addChannel</code> ones, to build |
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| 334 | up a completely new decay table for an existing particle. |
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| 335 | |
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| 336 | <p/> |
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| 337 | When adding new channels or changing branching ratios in general, |
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| 338 | note that, once a particle is to be decayed, the sum of branching |
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| 339 | ratios is always rescaled to unity. Beforehand, <code>rescaleBR</code> |
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| 340 | may be used to rescale an existing branching ratio by the given factor. |
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| 341 | |
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| 342 | <p/> |
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| 343 | There are a few commands that will study all the decay channels of the |
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| 344 | given particle, to switch them on or off as desired. The |
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| 345 | <pre> |
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| 346 | id:onMode = onMode |
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| 347 | </pre> |
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| 348 | will set the <code>onMode</code> property of all channels to the |
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| 349 | desired value. The |
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| 350 | <pre> |
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| 351 | id:offIfAny = product1 product2 .... |
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| 352 | id:onIfAny = product1 product2 .... |
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| 353 | id:onPosIfAny = product1 product2 .... |
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| 354 | id:onNegIfAny = product1 product2 .... |
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| 355 | </pre> |
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| 356 | will set the <code>onMode</code> 0, 1, 2 or 3, respectively, for all |
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| 357 | channels which contain any of the enumerated products, where the matching |
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| 358 | to these products is done without distinction of particles and |
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| 359 | antiparticles. Note that "<code>Pos</code>" and "<code>Neg</code>" |
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| 360 | are slightly misleading since it refers to the particle and antiparticle |
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| 361 | of the <code>id</code> species rather than charge, but should still be |
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| 362 | simpler to remember and understand than alternative notations. |
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| 363 | Correspondingly |
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| 364 | <pre> |
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| 365 | id:offIfAll = product1 product2 .... |
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| 366 | id:onIfAll = product1 product2 .... |
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| 367 | id:onPosIfAll = product1 product2 .... |
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| 368 | id:onNegIfAll = product1 product2 .... |
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| 369 | </pre> |
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| 370 | will set the <code>onMode</code> 0, 1, 2 or 3, respectively, for all |
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| 371 | channels which contain all of the enumerated products, again without |
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| 372 | distinction of particles and antiparticles. If the same product appears |
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| 373 | twice in the list it must also appear twice in the decay channel, and |
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| 374 | so on. The decay channel is allowed to contain further particles, |
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| 375 | beyond the product list. By contrast, |
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| 376 | <pre> |
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| 377 | id:offIfMatch = product1 product2 .... |
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| 378 | id:onIfMatch = product1 product2 .... |
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| 379 | id:onPosIfMatch = product1 product2 .... |
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| 380 | id:onPosIfMatch = product1 product2 .... |
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| 381 | </pre> |
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| 382 | requires the decay-channel multiplicity to agree with that of the product |
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| 383 | list, but otherwise works as the <code>onIfAll/offIfAll</code> methods. |
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| 384 | |
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| 385 | <p/> |
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| 386 | Note that the action of several of the commands depends on the order |
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| 387 | in which they are executed, as one would logically expect. For instance, |
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| 388 | <code>id:oneChannel</code> removes all decay channels of <code>id</code> |
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| 389 | and thus all previous changes in this decay table, while subsequent |
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| 390 | additions or changes would still take effect. Another example would be that |
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| 391 | <code>23:onMode = off</code> followed by <code>23:onIfAny = 1 2 3 4 5</code> |
|---|
| 392 | would let the <i>Z^0</i> decay to quarks, while no decays would be |
|---|
| 393 | allowed if the order were to be reversed. |
|---|
| 394 | |
|---|
| 395 | <p/> |
|---|
| 396 | b) The <code>Pythia</code> <code>readString(string)</code> method actually |
|---|
| 397 | does not do changes itself, but sends on the string either to the |
|---|
| 398 | <code>ParticleData</code> class or to the <code>Settings</code> one, |
|---|
| 399 | depending on whether the string begins with a digit or a letter. |
|---|
| 400 | If desired, it is possible to communicate directly with the corresponding |
|---|
| 401 | <code>ParticleData</code> method: |
|---|
| 402 | <pre> |
|---|
| 403 | pythia.particleData.readString("111:mayDecay = off"); |
|---|
| 404 | pythia.particleData.readString("15:2:products = 16 -211"); |
|---|
| 405 | </pre> |
|---|
| 406 | In this case, changes intended for <code>Settings</code> would not be |
|---|
| 407 | understood. |
|---|
| 408 | |
|---|
| 409 | <p/> |
|---|
| 410 | c) Underlying this are commands for all the individual properties in |
|---|
| 411 | the <code>ParticleData</code> class, one for each. These are |
|---|
| 412 | further described below. Thus, an example now reads |
|---|
| 413 | <pre> |
|---|
| 414 | pythia.particleData.mayDecay(111, false); |
|---|
| 415 | </pre> |
|---|
| 416 | Boolean values should here be given as <code>true</code> or |
|---|
| 417 | <code>false</code>. |
|---|
| 418 | |
|---|
| 419 | <p/> |
|---|
| 420 | d) A simpler and more useful way is to collect all your changes |
|---|
| 421 | in a separate file, with one line per change, e.g. |
|---|
| 422 | <pre> |
|---|
| 423 | 111:mayDecay = off |
|---|
| 424 | </pre> |
|---|
| 425 | The file can be read by the |
|---|
| 426 | <pre> |
|---|
| 427 | pythia.readFile(fileName); |
|---|
| 428 | </pre> |
|---|
| 429 | method, where <code>fileName</code> is a string, e.g. |
|---|
| 430 | <code>pythia.readFile("main.cmnd")</code> (or an <code>istream</code> |
|---|
| 431 | instead of a <code>fileName</code>). Each line is processed as |
|---|
| 432 | described for the string in 2a). This file can freely mix commands to |
|---|
| 433 | the <code>Settings</code> and <code>ParticleData</code> classes. |
|---|
| 434 | </li> |
|---|
| 435 | |
|---|
| 436 | <li> <p/> |
|---|
| 437 | A routine <code>reInit(fileName)</code> is provided, and can be used to |
|---|
| 438 | zero the particle data table and reinitialize it from scratch. |
|---|
| 439 | Such a call might be useful if several subruns are to be made with |
|---|
| 440 | widely different particle data - normally the maps are only built |
|---|
| 441 | from scratch once, namely when the <code>Pythia()</code> object is |
|---|
| 442 | created. Also, there is no other possibility to restore the default |
|---|
| 443 | values, unlike for the settings. |
|---|
| 444 | </li> |
|---|
| 445 | |
|---|
| 446 | <li> <p/> |
|---|
| 447 | You may at any time obtain a listing of all the particle data by calling |
|---|
| 448 | <pre> |
|---|
| 449 | pythia.particleData.listAll(); |
|---|
| 450 | </pre> |
|---|
| 451 | The listing is by increasing <code>id</code> number. It shows the basic |
|---|
| 452 | quantities introduced above. Some are abbreviated in the header to fit on |
|---|
| 453 | the lines: <code>spn = spinType</code>, <code>chg = chargeType</code>, |
|---|
| 454 | <code>col = colType</code>, <code>res = isResonance</code>, |
|---|
| 455 | <code>dec = mayDecay && canDecay</code> (the latter checks that decay |
|---|
| 456 | channels have been defined), <code>ext = doExternalDecay</code>, |
|---|
| 457 | <code>vis = isVisible</code> and <code>wid = doForceWidth</code>.<br/> |
|---|
| 458 | |
|---|
| 459 | To list only those particles that were changed (one way or another, the |
|---|
| 460 | listing will not tell what property or decay channel was changed), instead use |
|---|
| 461 | <pre> |
|---|
| 462 | pythia.particleData.listChanged(); |
|---|
| 463 | </pre> |
|---|
| 464 | (This info is based on a further <code>hasChanged</code> flag of a particle |
|---|
| 465 | or a channel, set <code>true</code> whenever any of the changing methods are |
|---|
| 466 | used. It is possible to manipulate this value, but this is not recommended.) |
|---|
| 467 | By default the internal initialization of the widths of resonances such as |
|---|
| 468 | <i>gamma^*/Z^0, W^+-, t/tbar, H^0</i> do not count as changes; if you want |
|---|
| 469 | to list also those changes instead call <code>listChanged(true)</code>. |
|---|
| 470 | <br/> |
|---|
| 471 | |
|---|
| 472 | To list only one particle, give its <code>id</code> code as argument to |
|---|
| 473 | the <code>list(...)</code> function.. To list a restricted set of particles, |
|---|
| 474 | give in their <code>id</code> codes to <code>list(...)</code> as a |
|---|
| 475 | <code>vector<int></code>. |
|---|
| 476 | </li> |
|---|
| 477 | |
|---|
| 478 | <li> <p/> |
|---|
| 479 | For wholesale changes of particle properties all available data can be |
|---|
| 480 | written out, edited, and then read back in again. These methods are |
|---|
| 481 | mainly intended for expert users. You can choose between two alternative |
|---|
| 482 | syntaxes. |
|---|
| 483 | |
|---|
| 484 | <p/> |
|---|
| 485 | a) XML syntax, using the <code><particle</code> and |
|---|
| 486 | <code><channel</code> lines already described. You use the method |
|---|
| 487 | <code>particleData.listXML(fileName)</code> to produce such an XML |
|---|
| 488 | file and <code>particleData.readXML(fileName)</code> to read it back |
|---|
| 489 | in after editing. |
|---|
| 490 | |
|---|
| 491 | <p/> |
|---|
| 492 | b) Fixed/free format, using exactly the same information as illustrated |
|---|
| 493 | for the <code><particle</code> and <code><channel</code> lines |
|---|
| 494 | above, but now without any tags. This means that all information fields |
|---|
| 495 | must be provided (if there is no antiparticle then write |
|---|
| 496 | <code>void</code>), in the correct order (while the order is irrelevant |
|---|
| 497 | with XML syntax), and all on one line. Information is written out in |
|---|
| 498 | properly lined-up columns, but the reading is done using free format, |
|---|
| 499 | so fields need only be separated by at least one blank. Each new particle |
|---|
| 500 | is supposed to be separated by (at least) one blank line, whereas no |
|---|
| 501 | blank lines are allowed between the particle line and the subsequent |
|---|
| 502 | decay channel lines, if any. You use the method |
|---|
| 503 | <code>particleData.listFF(fileName)</code> to produce such a fixed/free |
|---|
| 504 | file and <code>particleData.readFF(fileName)</code> to read it back |
|---|
| 505 | in after editing. |
|---|
| 506 | |
|---|
| 507 | <p/> |
|---|
| 508 | As an alternative to the <code>readXML</code> and <code>readFF</code> |
|---|
| 509 | methods you can also use the |
|---|
| 510 | <code>particleData.reInit(fileName, xmlFormat)</code> method, where |
|---|
| 511 | <code>xmlFormat = true</code> (default) corresponds to reading an XML |
|---|
| 512 | file and <code>xmlFormat = false</code> to a fixed/free format one. |
|---|
| 513 | |
|---|
| 514 | <p/> |
|---|
| 515 | To check that the new particle and decay tables makes sense, you can use |
|---|
| 516 | the <code>particleData.checkTable()</code> method, either directly or by |
|---|
| 517 | switching it on among the standard |
|---|
| 518 | <a href="ErrorChecks.html" target="page">error checks</a>. |
|---|
| 519 | </li> |
|---|
| 520 | |
|---|
| 521 | </ol> |
|---|
| 522 | |
|---|
| 523 | <h2>The public methods</h2> |
|---|
| 524 | |
|---|
| 525 | In the following we present briefly the public methods in the three |
|---|
| 526 | classes used to build up the particle database. The order |
|---|
| 527 | is top-down, i.e from the full table of all particles to a single |
|---|
| 528 | particle to a single channel. |
|---|
| 529 | Note that these methods usually are less elegant and safe than the |
|---|
| 530 | input methods outlined above. If you use any of these methods, it is |
|---|
| 531 | likely to be the ones in the full database, i.e. the first ones to be |
|---|
| 532 | covered in the following. |
|---|
| 533 | |
|---|
| 534 | <p/> |
|---|
| 535 | For convenience, we have grouped related input and output methods |
|---|
| 536 | together. It should be obvious from the context which is which: |
|---|
| 537 | the input is of type <code>void</code> and has an extra last argument, |
|---|
| 538 | namely is the input value, while the output method returns a |
|---|
| 539 | quantity of the expected type. |
|---|
| 540 | |
|---|
| 541 | <h3>The ParticleData methods</h3> |
|---|
| 542 | |
|---|
| 543 | <a name="method1"></a> |
|---|
| 544 | <p/><strong>ParticleData::ParticleData() </strong> <br/> |
|---|
| 545 | the constructor has no arguments and does not do anything. Internal. |
|---|
| 546 | |
|---|
| 547 | |
|---|
| 548 | <a name="method2"></a> |
|---|
| 549 | <p/><strong>void ParticleData::initPtr(Info* infoPtr,Settings* settingsPtrIn, Rndm* rndmPtrIn, CoupSM* coupSMPtrIn) </strong> <br/> |
|---|
| 550 | initialize pointers to a few other classes. Internal. |
|---|
| 551 | |
|---|
| 552 | |
|---|
| 553 | <a name="method3"></a> |
|---|
| 554 | <p/><strong>bool ParticleData::init(string startFile = "../xmldoc/ParticleData.xml") </strong> <br/> |
|---|
| 555 | read in an XML-style file with particle data and initialize the |
|---|
| 556 | particle data tables accordingly. This command is executed |
|---|
| 557 | in the <code>Pythia</code> constructor, i.e. is mainly for |
|---|
| 558 | internal use. |
|---|
| 559 | <br/><code>argument</code><strong> startFile </strong> (<code>default = <strong>../xmldoc/ParticleData.xml</strong></code>) : |
|---|
| 560 | the name of the data file to be read. When called from the |
|---|
| 561 | <code>Pythia</code> constructor the directory is provided by the |
|---|
| 562 | <code><a href="ProgramFlow.html" target="page">PYTHIA8DATA</a></code> |
|---|
| 563 | environment variable, if set, else by the argument of this constructor, |
|---|
| 564 | which has the default value "../xmldoc". |
|---|
| 565 | |
|---|
| 566 | |
|---|
| 567 | |
|---|
| 568 | <a name="method4"></a> |
|---|
| 569 | <p/><strong>bool ParticleData::reInit(string startFile,bool xmlFormat = true) </strong> <br/> |
|---|
| 570 | overwrite the existing database by reading from the specified file. |
|---|
| 571 | Unlike <code>init</code> above this method is not called by the |
|---|
| 572 | <code>Pythia</code> constructor, but is entirely intended for users |
|---|
| 573 | who want to replace the existing particle data with their own. |
|---|
| 574 | <br/><code>argument</code><strong> startFile </strong> : the path and name of file to be read. |
|---|
| 575 | |
|---|
| 576 | <br/><code>argument</code><strong> xmlFormat </strong> : if true read the same kind of XML-style file |
|---|
| 577 | as used by <code>init</code>, if not use an alternative "free format" |
|---|
| 578 | file (i.e. without any XML tags, but with well-defined rules |
|---|
| 579 | specifying in which order properties are stored). |
|---|
| 580 | |
|---|
| 581 | |
|---|
| 582 | |
|---|
| 583 | <a name="method5"></a> |
|---|
| 584 | <p/><strong>void ParticleData::initWidths(vector<ResonanceWidths*> resonancePtrs) </strong> <br/> |
|---|
| 585 | initialize Breit-Wigner shape parameters for all particles, |
|---|
| 586 | and the detailed handling of resonances, i.e. particles with |
|---|
| 587 | perturbatively calculable partial widths, which can be used to |
|---|
| 588 | obtain a mass-dependent Breit-Wigner and a dynamic choice of |
|---|
| 589 | decay channels. Called from <code>Pythia::init()</code>. |
|---|
| 590 | |
|---|
| 591 | |
|---|
| 592 | <a name="method6"></a> |
|---|
| 593 | <p/><strong>bool ParticleData::readXML(string inFile, bool reset = true) </strong> <br/> |
|---|
| 594 | |
|---|
| 595 | <strong>void ParticleData::listXML(string outFile) </strong> <br/> |
|---|
| 596 | read in XML-style data from a file or write it out to a file. For the |
|---|
| 597 | former one can also decide whether to reset all particles to scratch, |
|---|
| 598 | or only overwrite those particles in the file. The former method is |
|---|
| 599 | used by <code>init</code> and <code>reInit</code> above. |
|---|
| 600 | |
|---|
| 601 | |
|---|
| 602 | <a name="method7"></a> |
|---|
| 603 | <p/><strong>bool ParticleData::readFF(string inFile, bool reset = true) </strong> <br/> |
|---|
| 604 | |
|---|
| 605 | <strong>void ParticleData::listFF(string outFile) </strong> <br/> |
|---|
| 606 | read in free-format-style data from a file or write it out to a file. |
|---|
| 607 | For the former one can also decide whether to reset all particles to |
|---|
| 608 | scratch, or only overwrite those particles in the file. The former |
|---|
| 609 | method is used by <code>reInit</code> above. |
|---|
| 610 | |
|---|
| 611 | |
|---|
| 612 | <a name="method8"></a> |
|---|
| 613 | <p/><strong>bool ParticleData::readString(string line, bool warn = true, ostream& os = cout) </strong> <br/> |
|---|
| 614 | read in a string and interpret is as a new or changed particle data. |
|---|
| 615 | The possibilities are extensively described above. It is normally |
|---|
| 616 | used indirectly, via <code>Pythia::readString(...)</code> and |
|---|
| 617 | <code>Pythia::readFile(...)</code>. |
|---|
| 618 | <br/><code>argument</code><strong> line </strong> : |
|---|
| 619 | the string to be interpreted as an instruction. |
|---|
| 620 | |
|---|
| 621 | <br/><code>argument</code><strong> warn </strong> (<code>default = <strong>true</strong></code>) : |
|---|
| 622 | write a warning message or not whenever the instruction does not make |
|---|
| 623 | sense, e.g. if the particle does not exist in the database. |
|---|
| 624 | |
|---|
| 625 | <br/><code>argument</code><strong> os </strong> (<code>default = <strong>cout</strong></code>) : |
|---|
| 626 | stream for error printout. |
|---|
| 627 | |
|---|
| 628 | <br/><b>Note:</b> the method returns false if it fails to |
|---|
| 629 | make sense out of the input string. |
|---|
| 630 | |
|---|
| 631 | |
|---|
| 632 | <a name="method9"></a> |
|---|
| 633 | <p/><strong>void ParticleData::listAll(ostream& os = cout) </strong> <br/> |
|---|
| 634 | |
|---|
| 635 | <strong>void ParticleData::listChanged(ostream& os = cout) </strong> <br/> |
|---|
| 636 | |
|---|
| 637 | <strong>void ParticleData::listChangedAndRes(ostream& os = cout) </strong> <br/> |
|---|
| 638 | |
|---|
| 639 | <strong>void ParticleData::list(bool changedOnly = false, bool changedRes = true, ostream& os = cout) </strong> <br/> |
|---|
| 640 | methods intended to present a listing of particle data in a readable |
|---|
| 641 | format. The first three are special cases of the fourth. The first |
|---|
| 642 | lists all particle data, the second only data for those particles that |
|---|
| 643 | were changed after the original creation of the particle data table. |
|---|
| 644 | Resonances are a special case since they can get their data changed |
|---|
| 645 | by being linked to an object that does the calculation of branching |
|---|
| 646 | ratios. The second method does not count such resonances as changed, |
|---|
| 647 | whereas the third does and thus lists all resonances. |
|---|
| 648 | |
|---|
| 649 | |
|---|
| 650 | <a name="method10"></a> |
|---|
| 651 | <p/><strong>void ParticleData::list(int idList, ostream& os = cout) </strong> <br/> |
|---|
| 652 | |
|---|
| 653 | <strong>void ParticleData::list(vector<int> idList, ostream& os = cout) </strong> <br/> |
|---|
| 654 | list particle data for one single particle, with the identity code as |
|---|
| 655 | input, or for a set of particles, with an input vector of identity codes. |
|---|
| 656 | |
|---|
| 657 | |
|---|
| 658 | <a name="method11"></a> |
|---|
| 659 | <p/><strong>void ParticleData::checkTable(ostream& os = cout) </strong> <br/> |
|---|
| 660 | |
|---|
| 661 | <strong>void ParticleData::checkTable(int verbosity,ostream& os = cout) </strong> <br/> |
|---|
| 662 | check that the particle decay table makes sense, especially for decays. |
|---|
| 663 | <br/><code>argument</code><strong> verbosity </strong> : level of checks. 0 is only mininal, |
|---|
| 664 | e.g. if a particle has no open decay channels. 1, which is the level |
|---|
| 665 | of the first method, provides warning if any individual channel is |
|---|
| 666 | closed, except for resonances. 2 also prints the |
|---|
| 667 | branching-ratio-averaged threshold mass. 11 and 12 are like 1 and 2, |
|---|
| 668 | but also include resonances in the detailed checks. |
|---|
| 669 | |
|---|
| 670 | |
|---|
| 671 | |
|---|
| 672 | <a name="method12"></a> |
|---|
| 673 | <p/><strong>void ParticleData::addParticle(int id, string name = " ", int spinType = 0, int chargeType = 0, int colType = 0, double m0 = 0., double mWidth = 0., double mMin = 0., double mMax = 0., double tau0 = 0.) </strong> <br/> |
|---|
| 674 | |
|---|
| 675 | <strong>void ParticleData::addParticle(int id, string name, string antiName, int spinType = 0, int chargeType = 0, int colType = 0, double m0 = 0., double mWidth = 0., double mMin = 0., double mMax = 0., double tau0 = 0.) </strong> <br/> |
|---|
| 676 | add a particle to the decay table; in the first form a partcle which is |
|---|
| 677 | its own antiparticle, in the second where a separate antiparticle exists. |
|---|
| 678 | |
|---|
| 679 | |
|---|
| 680 | <a name="method13"></a> |
|---|
| 681 | <p/><strong>void ParticleData::setAll(int id, string name, string antiName, int spinType = 0, int chargeType = 0, int colType = 0, double m0 = 0., double mWidth = 0., double mMin = 0., double mMax = 0.,double tau0 = 0.) </strong> <br/> |
|---|
| 682 | change all the properties of the particle associated with a given |
|---|
| 683 | identity code. |
|---|
| 684 | |
|---|
| 685 | |
|---|
| 686 | <a name="method14"></a> |
|---|
| 687 | <p/><strong>bool ParticleData::isParticle(int id) </strong> <br/> |
|---|
| 688 | query whether the particle data table contains the particle of the |
|---|
| 689 | identity code. |
|---|
| 690 | |
|---|
| 691 | |
|---|
| 692 | <a name="method15"></a> |
|---|
| 693 | <p/><strong>int ParticleData::nextId(int id) </strong> <br/> |
|---|
| 694 | return the identity code of the sequentially next particle stored in table. |
|---|
| 695 | |
|---|
| 696 | |
|---|
| 697 | <a name="method16"></a> |
|---|
| 698 | <p/><strong>bool ParticleData::hasAnti(int id) </strong> <br/> |
|---|
| 699 | bool whether a distinct antiparticle exists or not. Is true if an |
|---|
| 700 | antiparticle name has been set (and is different from |
|---|
| 701 | <code>void</code>). |
|---|
| 702 | |
|---|
| 703 | |
|---|
| 704 | <a name="method17"></a> |
|---|
| 705 | <p/><strong>void ParticleData::name(int id, string name) </strong> <br/> |
|---|
| 706 | |
|---|
| 707 | <strong>void ParticleData::antiName(int id, string antiName) </strong> <br/> |
|---|
| 708 | |
|---|
| 709 | <strong>void ParticleData::names(int id, string name, string antiName) </strong> <br/> |
|---|
| 710 | |
|---|
| 711 | <strong>string ParticleData::name(int id) </strong> <br/> |
|---|
| 712 | particle and antiparticle names are stored separately, the sign of |
|---|
| 713 | <code>id</code> determines which of the two is returned, with |
|---|
| 714 | <code>void</code> used to indicate the absence of an antiparticle. |
|---|
| 715 | |
|---|
| 716 | |
|---|
| 717 | <a name="method18"></a> |
|---|
| 718 | <p/><strong>void ParticleData::spinType(int id, int spinType) </strong> <br/> |
|---|
| 719 | |
|---|
| 720 | <strong>int ParticleData::spinType(int id) </strong> <br/> |
|---|
| 721 | the spin type, of the form <i>2 s + 1</i>, with special code 0 |
|---|
| 722 | for entries of unknown or indeterminate spin. |
|---|
| 723 | |
|---|
| 724 | |
|---|
| 725 | <a name="method19"></a> |
|---|
| 726 | <p/><strong>void ParticleData::chargeType(int id, int chargeType) </strong> <br/> |
|---|
| 727 | |
|---|
| 728 | <strong>int ParticleData::chargeType(int id) </strong> <br/> |
|---|
| 729 | three times the charge (to make it an integer), taking into account |
|---|
| 730 | the sign of <code>id</code>. |
|---|
| 731 | |
|---|
| 732 | |
|---|
| 733 | <a name="method20"></a> |
|---|
| 734 | <p/><strong>double ParticleData::charge(int id) </strong> <br/> |
|---|
| 735 | the electrical charge of a particle, equal to |
|---|
| 736 | <code>chargeType(id)/3</code>. |
|---|
| 737 | |
|---|
| 738 | |
|---|
| 739 | <a name="method21"></a> |
|---|
| 740 | <p/><strong>void ParticleData::colType(int id, int colType) </strong> <br/> |
|---|
| 741 | |
|---|
| 742 | <strong>int ParticleData::colType(int id) </strong> <br/> |
|---|
| 743 | the colour type, with 0 uncoloured, 1 triplet, -1 antitriplet and 2 |
|---|
| 744 | octet, taking into account the sign of <code>id</code>. |
|---|
| 745 | |
|---|
| 746 | |
|---|
| 747 | <a name="method22"></a> |
|---|
| 748 | <p/><strong>void ParticleData::m0(int id, double m0) </strong> <br/> |
|---|
| 749 | |
|---|
| 750 | <strong>double ParticleData::m0(int id) </strong> <br/> |
|---|
| 751 | the nominal mass <i>m_0</i> (in GeV). |
|---|
| 752 | |
|---|
| 753 | |
|---|
| 754 | <a name="method23"></a> |
|---|
| 755 | <p/><strong>void ParticleData::mWidth(int id, double mWidth) </strong> <br/> |
|---|
| 756 | |
|---|
| 757 | <strong>double ParticleData::mWidth(int id) </strong> <br/> |
|---|
| 758 | the width <i>Gamma</i> of the Breit-Wigner distribution (in GeV). |
|---|
| 759 | |
|---|
| 760 | |
|---|
| 761 | <a name="method24"></a> |
|---|
| 762 | <p/><strong>void ParticleData::mMin(int id, double mMin) </strong> <br/> |
|---|
| 763 | |
|---|
| 764 | <strong>double ParticleData::mMin(int id) </strong> <br/> |
|---|
| 765 | the lower limit of the allowed mass range generated by the Breit-Wigner |
|---|
| 766 | (in GeV). Has no meaning for particles without width, and would |
|---|
| 767 | typically be 0 there. |
|---|
| 768 | |
|---|
| 769 | |
|---|
| 770 | <a name="method25"></a> |
|---|
| 771 | <p/><strong>void ParticleData::mMax(int id, double mMax) </strong> <br/> |
|---|
| 772 | |
|---|
| 773 | <strong>double ParticleData::mMax(int id) </strong> <br/> |
|---|
| 774 | the upper limit of the allowed mass range generated by the Breit-Wigner |
|---|
| 775 | (in GeV). If <i>mMax < mMin</i> then no upper limit is imposed. |
|---|
| 776 | Has no meaning for particles without width, and would typically |
|---|
| 777 | be 0 there. |
|---|
| 778 | |
|---|
| 779 | |
|---|
| 780 | <a name="method26"></a> |
|---|
| 781 | <p/><strong>double ParticleData::m0Min(int id) </strong> <br/> |
|---|
| 782 | similar to <code>mMin()</code> above, except that for particles with |
|---|
| 783 | no width the <code>m0(id)</code> value is returned. |
|---|
| 784 | |
|---|
| 785 | |
|---|
| 786 | <a name="method27"></a> |
|---|
| 787 | <p/><strong>double ParticleData::m0Max(int id) </strong> <br/> |
|---|
| 788 | similar to <code>mMax()</code> above, except that for particles with |
|---|
| 789 | no width the <code>m0(id)</code> value is returned. |
|---|
| 790 | |
|---|
| 791 | |
|---|
| 792 | <a name="method28"></a> |
|---|
| 793 | <p/><strong>void ParticleData::tau0(int id, double tau0) </strong> <br/> |
|---|
| 794 | |
|---|
| 795 | <strong>double ParticleData::tau0(int id) </strong> <br/> |
|---|
| 796 | the nominal proper lifetime <i>tau_0</i> (in mm/c). |
|---|
| 797 | |
|---|
| 798 | |
|---|
| 799 | <a name="method29"></a> |
|---|
| 800 | <p/><strong>void ParticleData::isResonance(int id, bool isResonance) </strong> <br/> |
|---|
| 801 | |
|---|
| 802 | <strong>bool ParticleData::isResonance(int id) </strong> <br/> |
|---|
| 803 | a flag telling whether a particle species are considered as a resonance |
|---|
| 804 | or not. Here <a href="ResonanceDecays.html" target="page">"resonance"</a> |
|---|
| 805 | is used as shorthand for any massive particle |
|---|
| 806 | where the decay process should be counted as part of the hard process |
|---|
| 807 | itself, and thus be performed before showers and other event aspects |
|---|
| 808 | are added. Restrictions on allowed decay channels is also directly |
|---|
| 809 | reflected in the cross section of simulated processes, while those of |
|---|
| 810 | normal hadrons and other light particles are not. |
|---|
| 811 | In practice, it is reserved for states above the <i>b bbar</i> |
|---|
| 812 | bound systems in mass, i.e. for <i>W, Z, t</i>, Higgs states, |
|---|
| 813 | supersymmetric states and (most?) other states in any new theory. |
|---|
| 814 | All particles with <code>m0</code> above 20 GeV are by default |
|---|
| 815 | initialized to be considered as resonances. |
|---|
| 816 | |
|---|
| 817 | |
|---|
| 818 | <a name="method30"></a> |
|---|
| 819 | <p/><strong>void ParticleData::mayDecay(int id, bool mayDecay) </strong> <br/> |
|---|
| 820 | |
|---|
| 821 | <strong>bool ParticleData::mayDecay(int id) </strong> <br/> |
|---|
| 822 | a flag telling whether a particle species may decay or not, offering |
|---|
| 823 | the main user switch. Whether a given particle of this kind then actually |
|---|
| 824 | will decay also depends on it having allowed decay channels, and on |
|---|
| 825 | other flags for <a href="ParticleDecays.html" target="page">particle decays</a>. |
|---|
| 826 | All particles with <code>tau0</code> below 1000 mm are |
|---|
| 827 | by default initialized to allow decays. |
|---|
| 828 | |
|---|
| 829 | |
|---|
| 830 | <a name="method31"></a> |
|---|
| 831 | <p/><strong>void ParticleData::doExternalDecays(int id, bool doExternalDecays) </strong> <br/> |
|---|
| 832 | |
|---|
| 833 | <strong>bool ParticleData::doExternalDecay(int id) </strong> <br/> |
|---|
| 834 | a flag telling whether a particle should be handled by an external |
|---|
| 835 | decay package or not, with the latter default. Can be manipulated as |
|---|
| 836 | described on this page, but should normally not be. Instead the |
|---|
| 837 | <code><a href="ExternalDecays.html" target="page">pythia.decayPtr</a></code> |
|---|
| 838 | method should be provided with the list of relevant particles. |
|---|
| 839 | |
|---|
| 840 | |
|---|
| 841 | <a name="method32"></a> |
|---|
| 842 | <p/><strong>void ParticleData::isVisible(int id, bool isVisible) </strong> <br/> |
|---|
| 843 | |
|---|
| 844 | <strong>bool ParticleData::isVisible(int id) </strong> <br/> |
|---|
| 845 | a flag telling whether a particle species is to be considered as |
|---|
| 846 | visible in a detector or not, as used e.g. in analysis routines. |
|---|
| 847 | By default this includes neutrinos and a few BSM particles |
|---|
| 848 | (gravitino, sneutrinos, neutralinos) that have neither strong nor |
|---|
| 849 | electromagnetic charge, and are not made up of constituents that |
|---|
| 850 | have it. The value of this flag is only relevant if a particle is |
|---|
| 851 | long-lived enough actually to make it to a detector. |
|---|
| 852 | |
|---|
| 853 | |
|---|
| 854 | <a name="method33"></a> |
|---|
| 855 | <p/><strong>void ParticleData::doForceWidth(int id, bool doForceWidth) </strong> <br/> |
|---|
| 856 | |
|---|
| 857 | <strong>bool ParticleData::doForceWidth(int id) </strong> <br/> |
|---|
| 858 | a flag valid only for resonances where PYTHIA contains code to |
|---|
| 859 | calculate the width of the resonance from encoded matrix-element |
|---|
| 860 | expressions, i.e. the <i>Z^0</i>, <i>W^+-</i>, <i>t</i>, |
|---|
| 861 | <i>h^0</i>, and a few more. The normal behaviour (<code>false</code>) |
|---|
| 862 | is then that the width is calculated from the mass, but it is |
|---|
| 863 | possible to <a href="ResonanceDecays.html" target="page">force</a> the resonance |
|---|
| 864 | to retain the nominal width. Branching ratios and the running of the |
|---|
| 865 | total width are unaffected. |
|---|
| 866 | |
|---|
| 867 | |
|---|
| 868 | <a name="method34"></a> |
|---|
| 869 | <p/><strong>void ParticleData::hasChanged(int id, bool hasChanged) </strong> <br/> |
|---|
| 870 | |
|---|
| 871 | <strong>bool ParticleData::hasChanged(int id) </strong> <br/> |
|---|
| 872 | keep track of whether the data for a particle has been changed |
|---|
| 873 | in any respect between initialization and the current status. |
|---|
| 874 | Is used e.g. by the <code>listChanged</code> method to determine |
|---|
| 875 | which particles to list. |
|---|
| 876 | |
|---|
| 877 | |
|---|
| 878 | <a name="method35"></a> |
|---|
| 879 | <p/><strong>bool ParticleData::useBreitWigner(int id) </strong> <br/> |
|---|
| 880 | tells whether a particle will have a Breit-Wigner mass distribution or |
|---|
| 881 | not. Is determined by an internal logic based on the particle width and |
|---|
| 882 | on the value of the |
|---|
| 883 | <code><a href="ParticleData.html" target="page">ParticleData:modeBreitWigner</a></code> |
|---|
| 884 | switch. |
|---|
| 885 | |
|---|
| 886 | |
|---|
| 887 | <a name="method36"></a> |
|---|
| 888 | <p/><strong>double ParticleData::constituentMass(int id) </strong> <br/> |
|---|
| 889 | is the constituent mass for a quark, hardcoded as |
|---|
| 890 | <i>m_u = m_d = 0.325</i>, <i>m_s = 0.50</i>, <i>m_c = 1.60</i> |
|---|
| 891 | and <i>m_b = 5.0</i> GeV, for a diquark the sum of quark constituent |
|---|
| 892 | masses, and for everything else the same as the ordinary mass. |
|---|
| 893 | |
|---|
| 894 | |
|---|
| 895 | <a name="method37"></a> |
|---|
| 896 | <p/><strong>double ParticleData::mass(int id) </strong> <br/> |
|---|
| 897 | returns a mass distributed according to a truncated Breit-Wigner, |
|---|
| 898 | with parameters as described here. Is equal to <code>m0(id)</code> for |
|---|
| 899 | particles without width. |
|---|
| 900 | |
|---|
| 901 | |
|---|
| 902 | <a name="method38"></a> |
|---|
| 903 | <p/><strong>double ParticleData::mRun(int id, double mH) </strong> <br/> |
|---|
| 904 | calculate the running mass of species <code>id</code> when probed at a |
|---|
| 905 | hard mass scale of <code>mH</code>. Only applied to obtain the |
|---|
| 906 | running quark masses; for all other particle the normal fixed mass |
|---|
| 907 | is used. |
|---|
| 908 | |
|---|
| 909 | |
|---|
| 910 | <a name="method39"></a> |
|---|
| 911 | <p/><strong>bool ParticleData::canDecay(int id) </strong> <br/> |
|---|
| 912 | true for a particle with at least one decay channel defined. |
|---|
| 913 | |
|---|
| 914 | |
|---|
| 915 | <a name="method40"></a> |
|---|
| 916 | <p/><strong>bool ParticleData::isLepton(int id) </strong> <br/> |
|---|
| 917 | true for a lepton or an antilepton (including neutrinos). |
|---|
| 918 | |
|---|
| 919 | |
|---|
| 920 | <a name="method41"></a> |
|---|
| 921 | <p/><strong>bool ParticleData::isQuark(int id) </strong> <br/> |
|---|
| 922 | true for a quark or an antiquark. |
|---|
| 923 | |
|---|
| 924 | |
|---|
| 925 | <a name="method42"></a> |
|---|
| 926 | <p/><strong>bool ParticleData::isGluon(int id) </strong> <br/> |
|---|
| 927 | true for a gluon. |
|---|
| 928 | |
|---|
| 929 | |
|---|
| 930 | <a name="method43"></a> |
|---|
| 931 | <p/><strong>bool ParticleData::isDiquark(int id) </strong> <br/> |
|---|
| 932 | true for a diquark or antidiquark. |
|---|
| 933 | |
|---|
| 934 | |
|---|
| 935 | <a name="method44"></a> |
|---|
| 936 | <p/><strong>bool ParticleData::isParton() </strong> <br/> |
|---|
| 937 | true for a gluon, a quark or antiquark up to the b (but excluding top), |
|---|
| 938 | and a diquark or antidiquark consisting of quarks up to the b. |
|---|
| 939 | |
|---|
| 940 | |
|---|
| 941 | <a name="method45"></a> |
|---|
| 942 | <p/><strong>bool ParticleData::isHadron(int id) </strong> <br/> |
|---|
| 943 | true for a hadron (made up out of normal quarks and gluons, |
|---|
| 944 | i.e. not for R-hadrons and other exotic states). |
|---|
| 945 | |
|---|
| 946 | |
|---|
| 947 | <a name="method46"></a> |
|---|
| 948 | <p/><strong>bool ParticleData::isMeson(int id) </strong> <br/> |
|---|
| 949 | true for a meson. |
|---|
| 950 | |
|---|
| 951 | |
|---|
| 952 | <a name="method47"></a> |
|---|
| 953 | <p/><strong>bool ParticleData::isBaryon(int id) </strong> <br/> |
|---|
| 954 | true for a baryon or antibaryon. |
|---|
| 955 | |
|---|
| 956 | |
|---|
| 957 | <a name="method48"></a> |
|---|
| 958 | <p/><strong>bool ParticleData::isOctetHadron(int id) </strong> <br/> |
|---|
| 959 | true for an intermediate hadron-like state with a colour octet charge |
|---|
| 960 | as used in the colour octet model for |
|---|
| 961 | <a href="OniaProcesses.html" target="page">onia</a> production. |
|---|
| 962 | |
|---|
| 963 | |
|---|
| 964 | <a name="method49"></a> |
|---|
| 965 | <p/><strong>int ParticleData::heaviestQuark(int id) </strong> <br/> |
|---|
| 966 | extracts the heaviest quark or antiquark, i.e. one with largest |
|---|
| 967 | <code>id</code> number, for a hadron. |
|---|
| 968 | |
|---|
| 969 | |
|---|
| 970 | <a name="method50"></a> |
|---|
| 971 | <p/><strong>int ParticleData::baryonNumberType(int id) </strong> <br/> |
|---|
| 972 | is 1 for a quark, 2 for a diquark, 3 for a baryon, the same with a |
|---|
| 973 | minus sign for antiparticles, and else zero. |
|---|
| 974 | |
|---|
| 975 | |
|---|
| 976 | <a name="method51"></a> |
|---|
| 977 | <p/><strong>void ParticleData::rescaleBR(int id, double newSumBR = 1.) </strong> <br/> |
|---|
| 978 | rescales all partial branching ratios by a common factor, such that |
|---|
| 979 | the sum afterward becomes <code>newSumBR</code>. |
|---|
| 980 | |
|---|
| 981 | |
|---|
| 982 | <a name="method52"></a> |
|---|
| 983 | <p/><strong>void setResonancePtr(int id, ResonanceWidths* resonancePtr) </strong> <br/> |
|---|
| 984 | set a pointer for a particle kind to a <code>ResonanceWidths</code> object. |
|---|
| 985 | This is done, from inside <code>ParticleData::initWidths</code>, only for |
|---|
| 986 | resonances, i.e. for particles such as <i>Z^0</i>, <i>W^+-</i>, top, |
|---|
| 987 | Higgs, and new unstable states beyond the Standard Model. The presence |
|---|
| 988 | of such an object will allow a more dynamic calculation of partial and |
|---|
| 989 | total widths, as illustrated by the following methods. |
|---|
| 990 | |
|---|
| 991 | |
|---|
| 992 | <a name="method53"></a> |
|---|
| 993 | <p/><strong>void ParticleData::resInit(int id) </strong> <br/> |
|---|
| 994 | initialize the treatment of a resonance. |
|---|
| 995 | |
|---|
| 996 | |
|---|
| 997 | <a name="method54"></a> |
|---|
| 998 | <p/><strong>double ParticleData::resWidth(int id, double mHat, int idInFlav = 0, bool openOnly = false, bool setBR = false) </strong> <br/> |
|---|
| 999 | calculate the total with for a resonance of a given current mass, |
|---|
| 1000 | optionally including coupling to incoming flavour state (consider |
|---|
| 1001 | the <i>gamma*/Z^0</i> combination), optionally excluding decay |
|---|
| 1002 | channels that have been closed by the user, and optionally storing |
|---|
| 1003 | the results in the normal decay table. |
|---|
| 1004 | |
|---|
| 1005 | |
|---|
| 1006 | <a name="method55"></a> |
|---|
| 1007 | <p/><strong>double ParticleData::resWidthOpen(int id, double mHat, int idInFlav = 0) </strong> <br/> |
|---|
| 1008 | special case of <code>resWidth</code>, where only open channels are |
|---|
| 1009 | included, but results are not stored in the normal decay table. |
|---|
| 1010 | |
|---|
| 1011 | |
|---|
| 1012 | <a name="method56"></a> |
|---|
| 1013 | <p/><strong>double ParticleData::resWidthStore(int id, double mHat, int idInFlav = 0) </strong> <br/> |
|---|
| 1014 | special case of <code>resWidth</code>, where only open channels are |
|---|
| 1015 | included, and results are stored in the normal decay table. |
|---|
| 1016 | |
|---|
| 1017 | |
|---|
| 1018 | <a name="method57"></a> |
|---|
| 1019 | <p/><strong>double ParticleData::resOpenFrac(int id1, int id2 = 0, int id3 = 0) </strong> <br/> |
|---|
| 1020 | calculate the fraction of the full branching ratio that is left |
|---|
| 1021 | open by the user choice of allowed decay channels. Can be applied |
|---|
| 1022 | to a final state with up to three resonances. Since the procedure |
|---|
| 1023 | is multiplicative, it would be easy to generalize also to more. |
|---|
| 1024 | |
|---|
| 1025 | |
|---|
| 1026 | <a name="method58"></a> |
|---|
| 1027 | <p/><strong>double ParticleData::resWidthRescaleFactor(int id) </strong> <br/> |
|---|
| 1028 | the factor used to rescale all partial widths in case the total |
|---|
| 1029 | width is being forced to a specific value by the user. |
|---|
| 1030 | |
|---|
| 1031 | |
|---|
| 1032 | <a name="method59"></a> |
|---|
| 1033 | <p/><strong>double ParticleData::resWidthChan(int id,double mHat, int idAbs1 = 0, int idAbs2 = 0) </strong> <br/> |
|---|
| 1034 | special case to calculate one final-state width; currently only used |
|---|
| 1035 | for Higgs decay to <i>q qbar</i>, <i>g g</i> or |
|---|
| 1036 | <i>gamma gamma</i>. |
|---|
| 1037 | |
|---|
| 1038 | |
|---|
| 1039 | <a name="method60"></a> |
|---|
| 1040 | <p/><strong>ParticleDataEntry* ParticleData::particleDataEntryPtr(int id) </strong> <br/> |
|---|
| 1041 | returns a pointer to the <code>ParticleDataEntry</code> object. |
|---|
| 1042 | The methods in the next section can then be used to manipulate |
|---|
| 1043 | this object. |
|---|
| 1044 | |
|---|
| 1045 | |
|---|
| 1046 | <h3>The ParticleDataEntry methods</h3> |
|---|
| 1047 | |
|---|
| 1048 | Most of the methods that can be applied to a single |
|---|
| 1049 | <code>ParticleDataEntry</code> object are almost identical with |
|---|
| 1050 | those used above for the <code>ParticleData</code>, except |
|---|
| 1051 | that the <code>id</code> argument is no longer needed to find |
|---|
| 1052 | the right entry in the table. By and large, this makes direct |
|---|
| 1053 | access to the <code>ParticleDataEntry</code> methods superfluous. |
|---|
| 1054 | There are a few methods that are unique to each class, however. |
|---|
| 1055 | Furthermore, to avoid some naming ambiguities, many methods that |
|---|
| 1056 | set values begin with <code>set</code>. |
|---|
| 1057 | |
|---|
| 1058 | <a name="method61"></a> |
|---|
| 1059 | <p/><strong>ParticleDataEntry::ParticleDataEntry(int id = 0, string name = " ", int spinType = 0, int chargeType = 0, int colType = 0, double m0 = 0., double mWidth = 0., double mMin = 0., double mMax = 0., double tau0 = 0.) </strong> <br/> |
|---|
| 1060 | |
|---|
| 1061 | <strong>ParticleDataEntry::ParticleDataEntry(int id, string name, string antiName, int spinType = 0, int chargeType = 0, int colType = 0, double m0 = 0., double mWidth = 0., double mMin = 0., double mMax = 0., double tau0 = 0.) </strong> <br/> |
|---|
| 1062 | there are two alternative constructors, that both expect the |
|---|
| 1063 | properties of a particle as input. The first assumes that there |
|---|
| 1064 | is only one particle, thet latter that there is a |
|---|
| 1065 | particle-antiparticle pair (but if the antiparticle name is |
|---|
| 1066 | <code>void</code> one reverts back to the particle-only case). |
|---|
| 1067 | |
|---|
| 1068 | |
|---|
| 1069 | <a name="method62"></a> |
|---|
| 1070 | <p/><strong>ParticleDataEntry::~ParticleDataEntry </strong> <br/> |
|---|
| 1071 | the destructor is needed to delete any <code>ResonanceWidths</code> |
|---|
| 1072 | objects that have been created and linked to the respective particle. |
|---|
| 1073 | |
|---|
| 1074 | |
|---|
| 1075 | <a name="method63"></a> |
|---|
| 1076 | <p/><strong>void ParticleDataEntry::setDefaults() </strong> <br/> |
|---|
| 1077 | initialize some particle flags with default values, e.g. whether |
|---|
| 1078 | a particle is a resonance, may decay, or is visible. Is called from the |
|---|
| 1079 | constructors and from <code>setAll</code>. |
|---|
| 1080 | |
|---|
| 1081 | |
|---|
| 1082 | <a name="method64"></a> |
|---|
| 1083 | <p/><strong>void ParticleDataEntry::initPtr(ParticleData* particleDataPtrIn) </strong> <br/> |
|---|
| 1084 | initialize pointer back to the whole database (so that masses of |
|---|
| 1085 | decay products can be accessed, e.g.). |
|---|
| 1086 | |
|---|
| 1087 | |
|---|
| 1088 | <a name="method65"></a> |
|---|
| 1089 | <p/><strong>void ParticleDataEntry::setAll( string name, string antiName, int spinType = 0, int chargeType = 0, int colType = 0, double m0 = 0., double mWidth = 0., double mMin = 0., double mMax = 0.,double tau0 = 0.) </strong> <br/> |
|---|
| 1090 | change all the properties of the particle associated with a given |
|---|
| 1091 | identity code. |
|---|
| 1092 | |
|---|
| 1093 | |
|---|
| 1094 | <a name="method66"></a> |
|---|
| 1095 | <p/><strong>int ParticleDataEntry::id() </strong> <br/> |
|---|
| 1096 | the PDG identity code. |
|---|
| 1097 | |
|---|
| 1098 | |
|---|
| 1099 | <a name="method67"></a> |
|---|
| 1100 | <p/><strong>bool ParticleDataEntry::hasAnti() </strong> <br/> |
|---|
| 1101 | tell whether a separate antiparticle exists. |
|---|
| 1102 | |
|---|
| 1103 | |
|---|
| 1104 | <a name="method68"></a> |
|---|
| 1105 | <p/><strong>void ParticleDataEntry::setName(string name) </strong> <br/> |
|---|
| 1106 | |
|---|
| 1107 | <strong>void ParticleDataEntry::setAntiName(string antiName) </strong> <br/> |
|---|
| 1108 | |
|---|
| 1109 | <strong>void ParticleDataEntry::setNames(string name,string antiName) </strong> <br/> |
|---|
| 1110 | |
|---|
| 1111 | <strong>string ParticleDataEntry::name(int id = 1) </strong> <br/> |
|---|
| 1112 | set or get the particle or antiparticle name. Only the sign of |
|---|
| 1113 | <code>id</code> is needed to distinguish particle/antiparticle. |
|---|
| 1114 | |
|---|
| 1115 | |
|---|
| 1116 | <a name="method69"></a> |
|---|
| 1117 | <p/><strong>void ParticleDataEntry::setSpinType(int spinType) </strong> <br/> |
|---|
| 1118 | |
|---|
| 1119 | <strong>int ParticleDataEntry::spinType() </strong> <br/> |
|---|
| 1120 | set or get the particle spin type, i.e. <i>2 s + 1</i>, or 0 in some |
|---|
| 1121 | special cases. |
|---|
| 1122 | |
|---|
| 1123 | |
|---|
| 1124 | <a name="method70"></a> |
|---|
| 1125 | <p/><strong>void ParticleDataEntry::setChargeType(int chargeType) </strong> <br/> |
|---|
| 1126 | |
|---|
| 1127 | <strong>int ParticleDataEntry::chargeType(int id = 1) </strong> <br/> |
|---|
| 1128 | |
|---|
| 1129 | <strong>double ParticleDataEntry::charge(int id = 1) </strong> <br/> |
|---|
| 1130 | set or get the particle charge type, i.e. three times the charge, |
|---|
| 1131 | or the charge itself. Only the sign of <code>id</code> is needed |
|---|
| 1132 | to distinguish particle/antiparticle. |
|---|
| 1133 | |
|---|
| 1134 | |
|---|
| 1135 | <a name="method71"></a> |
|---|
| 1136 | <p/><strong>void ParticleDataEntry::setColType(int colType) </strong> <br/> |
|---|
| 1137 | |
|---|
| 1138 | <strong>int ParticleDataEntry::colType(int id = 1) </strong> <br/> |
|---|
| 1139 | set or get the particle colour type, 0 for singlet, 1 for triplet, |
|---|
| 1140 | -1 for antitriplet, 2 for octet. Only the sign of <code>id</code> |
|---|
| 1141 | is needed to distinguish particle/antiparticle. |
|---|
| 1142 | |
|---|
| 1143 | |
|---|
| 1144 | <a name="method72"></a> |
|---|
| 1145 | <p/><strong>void ParticleDataEntry::setM0(double m0) </strong> <br/> |
|---|
| 1146 | |
|---|
| 1147 | <strong>double ParticleDataEntry::m0() </strong> <br/> |
|---|
| 1148 | the nominal mass <i>m_0</i> (in GeV). |
|---|
| 1149 | |
|---|
| 1150 | |
|---|
| 1151 | <a name="method73"></a> |
|---|
| 1152 | <p/><strong>void ParticleDataEntry::setMWidth(double mWidth) </strong> <br/> |
|---|
| 1153 | |
|---|
| 1154 | <strong>double ParticleDataEntry::mWidth() </strong> <br/> |
|---|
| 1155 | the width <i>Gamma</i> of the Breit-Wigner distribution (in GeV). |
|---|
| 1156 | |
|---|
| 1157 | |
|---|
| 1158 | <a name="method74"></a> |
|---|
| 1159 | <p/><strong>void ParticleDataEntry::setMMin(double mMin) </strong> <br/> |
|---|
| 1160 | |
|---|
| 1161 | <strong>double ParticleDataEntry::mMin() </strong> <br/> |
|---|
| 1162 | the lower limit of the allowed mass range generated by the Breit-Wigner |
|---|
| 1163 | (in GeV). Has no meaning for particles without width, and would |
|---|
| 1164 | typically be 0 there. |
|---|
| 1165 | |
|---|
| 1166 | |
|---|
| 1167 | <a name="method75"></a> |
|---|
| 1168 | <p/><strong>void ParticleDataEntry::setMMax(double mMax) </strong> <br/> |
|---|
| 1169 | |
|---|
| 1170 | <strong>double ParticleDataEntry::mMax() </strong> <br/> |
|---|
| 1171 | the upper limit of the allowed mass range generated by the Breit-Wigner |
|---|
| 1172 | (in GeV). If <i>mMax < mMin</i> then no upper limit is imposed. |
|---|
| 1173 | Has no meaning for particles without width, and would typically |
|---|
| 1174 | be 0 there. |
|---|
| 1175 | |
|---|
| 1176 | |
|---|
| 1177 | <a name="method76"></a> |
|---|
| 1178 | <p/><strong>double ParticleDataEntry::m0Min() </strong> <br/> |
|---|
| 1179 | similar to <code>mMin()</code> above, except that for particles with |
|---|
| 1180 | no width the <code>m0(id)</code> value is returned. |
|---|
| 1181 | |
|---|
| 1182 | |
|---|
| 1183 | <a name="method77"></a> |
|---|
| 1184 | <p/><strong>double ParticleDataEntry::m0Max() </strong> <br/> |
|---|
| 1185 | similar to <code>mMax()</code> above, except that for particles with |
|---|
| 1186 | no width the <code>m0(id)</code> value is returned. |
|---|
| 1187 | |
|---|
| 1188 | |
|---|
| 1189 | <a name="method78"></a> |
|---|
| 1190 | <p/><strong>void ParticleDataEntry::setTau0(double tau0) </strong> <br/> |
|---|
| 1191 | |
|---|
| 1192 | <strong>double ParticleDataEntry::tau0() </strong> <br/> |
|---|
| 1193 | the nominal proper lifetime <i>tau_0</i> (in mm/c). |
|---|
| 1194 | |
|---|
| 1195 | |
|---|
| 1196 | <a name="method79"></a> |
|---|
| 1197 | <p/><strong>void ParticleDataEntry::setIsResonance(bool isResonance) </strong> <br/> |
|---|
| 1198 | |
|---|
| 1199 | <strong>bool ParticleDataEntry::isResonance() </strong> <br/> |
|---|
| 1200 | a flag telling whether a particle species are considered as a resonance |
|---|
| 1201 | or not. Here <a href="ResonanceDecays.html" target="page">"resonance"</a> |
|---|
| 1202 | is used as shorthand for any massive particle |
|---|
| 1203 | where the decay process should be counted as part of the hard process |
|---|
| 1204 | itself, and thus be performed before showers and other event aspects |
|---|
| 1205 | are added. Restrictions on allowed decay channels is also directly |
|---|
| 1206 | reflected in the cross section of simulated processes, while those of |
|---|
| 1207 | normal hadrons and other light particles are not. |
|---|
| 1208 | In practice, it is reserved for states above the <i>b bbar</i> |
|---|
| 1209 | bound systems in mass, i.e. for <i>W, Z, t</i>, Higgs states, |
|---|
| 1210 | supersymmetric states and (most?) other states in any new theory. |
|---|
| 1211 | All particles with <code>m0</code> above 20 GeV are by default |
|---|
| 1212 | initialized to be considered as resonances. |
|---|
| 1213 | |
|---|
| 1214 | |
|---|
| 1215 | <a name="method80"></a> |
|---|
| 1216 | <p/><strong>void ParticleDataEntry::setMayDecay(bool mayDecay) </strong> <br/> |
|---|
| 1217 | |
|---|
| 1218 | <strong>bool ParticleDataEntry::mayDecay() </strong> <br/> |
|---|
| 1219 | a flag telling whether a particle species may decay or not, offering |
|---|
| 1220 | the main user switch. Whether a given particle of this kind then actually |
|---|
| 1221 | will decay also depends on it having allowed decay channels, and on |
|---|
| 1222 | other flags for <a href="ParticleDecays.html" target="page">particle decays</a>. |
|---|
| 1223 | All particles with <code>tau0</code> below 1000 mm are |
|---|
| 1224 | by default initialized to allow decays. |
|---|
| 1225 | |
|---|
| 1226 | |
|---|
| 1227 | <a name="method81"></a> |
|---|
| 1228 | <p/><strong>void ParticleDataEntry::setDoExternalDecays(bool doExternalDecays) </strong> <br/> |
|---|
| 1229 | |
|---|
| 1230 | <strong>bool ParticleDataEntry::doExternalDecay() </strong> <br/> |
|---|
| 1231 | a flag telling whether a particle should be handled by an external |
|---|
| 1232 | decay package or not, with the latter default. Can be manipulated as |
|---|
| 1233 | described on this page, but should normally not be. Instead the |
|---|
| 1234 | <code><a href="ExternalDecays.html" target="page">pythia.decayPtr</a></code> |
|---|
| 1235 | method should be provided with the list of relevant particles. |
|---|
| 1236 | |
|---|
| 1237 | |
|---|
| 1238 | <a name="method82"></a> |
|---|
| 1239 | <p/><strong>void ParticleDataEntry::setIsVisible(bool isVisible) </strong> <br/> |
|---|
| 1240 | |
|---|
| 1241 | <strong>bool ParticleDataEntry::isVisible() </strong> <br/> |
|---|
| 1242 | a flag telling whether a particle species is to be considered as |
|---|
| 1243 | visible in a detector or not, as used e.g. in analysis routines. |
|---|
| 1244 | By default this includes neutrinos and a few BSM particles |
|---|
| 1245 | (gravitino, sneutrinos, neutralinos) that have neither strong nor |
|---|
| 1246 | electromagnetic charge, and are not made up of constituents that |
|---|
| 1247 | have it. The value of this flag is only relevant if a particle is |
|---|
| 1248 | long-lived enough actually to make it to a detector. |
|---|
| 1249 | |
|---|
| 1250 | |
|---|
| 1251 | <a name="method83"></a> |
|---|
| 1252 | <p/><strong>void ParticleDataEntry::setDoForceWidth(bool doForceWidth) </strong> <br/> |
|---|
| 1253 | |
|---|
| 1254 | <strong>bool ParticleDataEntry::doForceWidth() </strong> <br/> |
|---|
| 1255 | a flag valid only for resonances where PYTHIA contains code to |
|---|
| 1256 | calculate the width of the resonance from encoded matrix-element |
|---|
| 1257 | expressions, i.e. the <i>Z^0</i>, <i>W^+-</i>, <i>t</i>, |
|---|
| 1258 | <i>h^0</i>, and a few more. The normal behaviour (<code>false</code>) |
|---|
| 1259 | is then that the width is calculated from the mass, but it is |
|---|
| 1260 | possible to <a href="ResonanceDecays.html" target="page">force</a> the resonance |
|---|
| 1261 | to retain the nominal width. Branching ratios and the running of the |
|---|
| 1262 | total width are unaffected. |
|---|
| 1263 | |
|---|
| 1264 | |
|---|
| 1265 | <a name="method84"></a> |
|---|
| 1266 | <p/><strong>void ParticleDataEntry::setHasChanged(bool hasChanged) </strong> <br/> |
|---|
| 1267 | |
|---|
| 1268 | <a name="method85"></a> |
|---|
| 1269 | <p/><strong>void ParticleDataEntry::hasChanged(bool hasChanged) </strong> <br/> |
|---|
| 1270 | keep track of whether the data for a particle has been changed |
|---|
| 1271 | in any respect between initialization and the current status. |
|---|
| 1272 | Is used e.g. by the <code>ParticleData::listChanged</code> method |
|---|
| 1273 | to determine which particles to list. |
|---|
| 1274 | |
|---|
| 1275 | |
|---|
| 1276 | <a name="method86"></a> |
|---|
| 1277 | <p/><strong>void ParticleDataEntry::initBWmass() </strong> <br/> |
|---|
| 1278 | Prepare the Breit-Wigner mass selection by precalculating |
|---|
| 1279 | frequently-used expressions. |
|---|
| 1280 | |
|---|
| 1281 | |
|---|
| 1282 | <a name="method87"></a> |
|---|
| 1283 | <p/><strong>double ParticleDataEntry::constituentMass() </strong> <br/> |
|---|
| 1284 | is the constituent mass for a quark, hardcoded as |
|---|
| 1285 | <i>m_u = m_d = 0.325</i>, <i>m_s = 0.50</i>, <i>m_c = 1.60</i> |
|---|
| 1286 | and <i>m_b = 5.0</i> GeV, for a diquark the sum of quark constituent |
|---|
| 1287 | masses, and for everything else the same as the ordinary mass. |
|---|
| 1288 | |
|---|
| 1289 | |
|---|
| 1290 | <a name="method88"></a> |
|---|
| 1291 | <p/><strong>double ParticleDataEntry::mass() </strong> <br/> |
|---|
| 1292 | give the mass of a particle, either at the nominal value |
|---|
| 1293 | or picked according to a (linear or quadratic) Breit-Wigner. |
|---|
| 1294 | |
|---|
| 1295 | |
|---|
| 1296 | <a name="method89"></a> |
|---|
| 1297 | <p/><strong>double ParticleDataEntry::mRun(double mH) </strong> <br/> |
|---|
| 1298 | calculate the running quark mass at a hard scale <code>mH</code>. |
|---|
| 1299 | For other particles the on-shell mass is given. |
|---|
| 1300 | |
|---|
| 1301 | |
|---|
| 1302 | <a name="method90"></a> |
|---|
| 1303 | <p/><strong>bool ParticleDataEntry::useBreitWigner() </strong> <br/> |
|---|
| 1304 | tells whether a particle will have a Breit-Wigner mass distribution or |
|---|
| 1305 | not. Is determined by an internal logic based on the particle width and |
|---|
| 1306 | on the value of the <code><a href="ParticleData.html" target="page"> |
|---|
| 1307 | ParticleData:modeBreitWigner</a></code> switch. |
|---|
| 1308 | |
|---|
| 1309 | |
|---|
| 1310 | <a name="method91"></a> |
|---|
| 1311 | <p/><strong>bool ParticleDataEntry::canDecay(int id) </strong> <br/> |
|---|
| 1312 | true for a particle with at least one decay channel defined. |
|---|
| 1313 | |
|---|
| 1314 | |
|---|
| 1315 | <a name="method92"></a> |
|---|
| 1316 | <p/><strong>bool ParticleDataEntry::isLepton() </strong> <br/> |
|---|
| 1317 | true for a lepton or an antilepton (including neutrinos). |
|---|
| 1318 | |
|---|
| 1319 | |
|---|
| 1320 | <a name="method93"></a> |
|---|
| 1321 | <p/><strong>bool ParticleDataEntry::isQuark() </strong> <br/> |
|---|
| 1322 | true for a quark or an antiquark. |
|---|
| 1323 | |
|---|
| 1324 | |
|---|
| 1325 | <a name="method94"></a> |
|---|
| 1326 | <p/><strong>bool ParticleDataEntry::isGluon() </strong> <br/> |
|---|
| 1327 | true for a gluon. |
|---|
| 1328 | |
|---|
| 1329 | |
|---|
| 1330 | <a name="method95"></a> |
|---|
| 1331 | <p/><strong>bool ParticleDataEntry::isDiquark() </strong> <br/> |
|---|
| 1332 | true for a diquark or antidiquark. |
|---|
| 1333 | |
|---|
| 1334 | |
|---|
| 1335 | <a name="method96"></a> |
|---|
| 1336 | <p/><strong>bool ParticleDataEntry::isParton() </strong> <br/> |
|---|
| 1337 | true for a gluon, a quark or antiquark up to the b (but excluding top), |
|---|
| 1338 | and a diquark or antidiquark consisting of quarks up to the b. |
|---|
| 1339 | |
|---|
| 1340 | |
|---|
| 1341 | <a name="method97"></a> |
|---|
| 1342 | <p/><strong>bool ParticleDataEntry::isHadron() </strong> <br/> |
|---|
| 1343 | true for a hadron (made up out of normal quarks and gluons, |
|---|
| 1344 | i.e. not for R-hadrons and other exotic states). |
|---|
| 1345 | |
|---|
| 1346 | |
|---|
| 1347 | <a name="method98"></a> |
|---|
| 1348 | <p/><strong>bool ParticleDataEntry::isMeson() </strong> <br/> |
|---|
| 1349 | true for a meson. |
|---|
| 1350 | |
|---|
| 1351 | |
|---|
| 1352 | <a name="method99"></a> |
|---|
| 1353 | <p/><strong>bool ParticleDataEntry::isBaryon() </strong> <br/> |
|---|
| 1354 | true for a baryon or antibaryon. |
|---|
| 1355 | |
|---|
| 1356 | |
|---|
| 1357 | <a name="method100"></a> |
|---|
| 1358 | <p/><strong>bool ParticleDataEntry::isOctetHadron() </strong> <br/> |
|---|
| 1359 | true for an intermediate hadron-like state with a colour octet charge |
|---|
| 1360 | as used in the colour octet model for |
|---|
| 1361 | <a href="OniaProcesses.html" target="page">onia</a> production. |
|---|
| 1362 | |
|---|
| 1363 | |
|---|
| 1364 | <a name="method101"></a> |
|---|
| 1365 | <p/><strong>int ParticleDataEntry::heaviestQuark(int id) </strong> <br/> |
|---|
| 1366 | extracts the heaviest quark or antiquark, i.e. one with largest |
|---|
| 1367 | <code>id</code> number, for a hadron. Only the sign of the input |
|---|
| 1368 | argument is relevant. |
|---|
| 1369 | |
|---|
| 1370 | |
|---|
| 1371 | <a name="method102"></a> |
|---|
| 1372 | <p/><strong>int ParticleDataEntry::baryonNumberType(int id) </strong> <br/> |
|---|
| 1373 | is 1 for a quark, 2 for a diquark, 3 for a baryon, the same with a |
|---|
| 1374 | minus sign for antiparticles, and else zero. Only the sign of the |
|---|
| 1375 | input argument is relevant. |
|---|
| 1376 | |
|---|
| 1377 | |
|---|
| 1378 | <a name="method103"></a> |
|---|
| 1379 | <p/><strong>void ParticleDataEntry::clearChannels() </strong> <br/> |
|---|
| 1380 | resets to an empty decay table. |
|---|
| 1381 | |
|---|
| 1382 | |
|---|
| 1383 | <a name="method104"></a> |
|---|
| 1384 | <p/><strong>void ParticleDataEntry::addChannel(int onMode = 0, double bRatio = 0., int meMode = 0, int prod0 = 0, int prod1 = 0,int prod2 = 0, int prod3 = 0, int prod4 = 0, int prod5 = 0, int prod6 = 0, int prod7 = 0,) </strong> <br/> |
|---|
| 1385 | adds a decay channel with up to 8 products. |
|---|
| 1386 | |
|---|
| 1387 | |
|---|
| 1388 | <a name="method105"></a> |
|---|
| 1389 | <p/><strong>int ParticleDataEntry::sizeChannels() </strong> <br/> |
|---|
| 1390 | returns the number of decay channels for a particle. |
|---|
| 1391 | |
|---|
| 1392 | |
|---|
| 1393 | <a name="method106"></a> |
|---|
| 1394 | <p/><strong>DecayChannel& ParticleDataEntry::channel(int i) </strong> <br/> |
|---|
| 1395 | |
|---|
| 1396 | <strong>const DecayChannel& ParticleDataEntry::channel(int i) </strong> <br/> |
|---|
| 1397 | gain access to a specified channel in the decay table. |
|---|
| 1398 | |
|---|
| 1399 | |
|---|
| 1400 | <a name="method107"></a> |
|---|
| 1401 | <p/><strong>void ParticleDataEntry::rescaleBR(double newSumBR = 1.) </strong> <br/> |
|---|
| 1402 | rescales all partial branching ratios by a common factor, such that |
|---|
| 1403 | the sum afterward becomes <code>newSumBR</code>. |
|---|
| 1404 | |
|---|
| 1405 | |
|---|
| 1406 | <a name="method108"></a> |
|---|
| 1407 | <p/><strong>bool ParticleDataEntry::preparePick(int idSgn, double mHat = 0., int idInFlav = 0) </strong> <br/> |
|---|
| 1408 | prepare to pick a decay channel. |
|---|
| 1409 | |
|---|
| 1410 | |
|---|
| 1411 | <a name="method109"></a> |
|---|
| 1412 | <p/><strong>DecayChannel& ParticleDataEntry::pickChannel() </strong> <br/> |
|---|
| 1413 | pick a decay channel according to branching ratios from |
|---|
| 1414 | <code>preparePick</code>. |
|---|
| 1415 | |
|---|
| 1416 | |
|---|
| 1417 | <a name="method110"></a> |
|---|
| 1418 | <p/><strong>void ParticleDataEntry::setResonancePtr(ResonanceWidths* resonancePtr) </strong> <br/> |
|---|
| 1419 | |
|---|
| 1420 | <strong>ResonanceWidths* ParticleDataEntry::getResonancePtr() </strong> <br/> |
|---|
| 1421 | set or get a pointer to an object that can be used for dynamic calculation |
|---|
| 1422 | of partial and total resonance widths. Here a resonance is a particle |
|---|
| 1423 | such as top, <i>Z^0</i>, <i>W^+-</i>, Higgs, and new unstable states |
|---|
| 1424 | beyond the Standard Model. |
|---|
| 1425 | |
|---|
| 1426 | |
|---|
| 1427 | <a name="method111"></a> |
|---|
| 1428 | <p/><strong>void ParticleDataEntry::resInit(Info* infoPtrIn, Settings* settingsPtrIn, ParticleData* particleDataPtrIn, CoupSM* coupSMPtrIn) </strong> <br/> |
|---|
| 1429 | initialize the treatment of a resonance. |
|---|
| 1430 | |
|---|
| 1431 | |
|---|
| 1432 | <a name="method112"></a> |
|---|
| 1433 | <p/><strong>double ParticleDataEntry::resWidth(int idSgn,double mHat, int idInFlav = 0, bool openOnly = false, bool setBR = false) </strong> <br/> |
|---|
| 1434 | calculate the total with for a resonance of a given current mass, |
|---|
| 1435 | optionally including coupling to incoming flavour state (consider |
|---|
| 1436 | the <i>gamma*/Z^0</i> combination), optionally excluding decay |
|---|
| 1437 | channels that have been closed by the user, and optionally storing |
|---|
| 1438 | the results in the normal decay table. For the first argument only |
|---|
| 1439 | the sign is relevant. |
|---|
| 1440 | |
|---|
| 1441 | |
|---|
| 1442 | <a name="method113"></a> |
|---|
| 1443 | <p/><strong>double ParticleDataEntry::resWidthOpen(int idSgn,double mHat, int idInFlav = 0) </strong> <br/> |
|---|
| 1444 | special case of <code>resWidth</code>, where only open channels are |
|---|
| 1445 | included, but results are not stored in the normal decay table. |
|---|
| 1446 | |
|---|
| 1447 | |
|---|
| 1448 | <a name="method114"></a> |
|---|
| 1449 | <p/><strong>double ParticleDataEntry::resWidthStore(int idSgn,double mHat, int idInFlav = 0) </strong> <br/> |
|---|
| 1450 | special case of <code>resWidth</code>, where only open channels are |
|---|
| 1451 | included, and results are stored in the normal decay table. |
|---|
| 1452 | |
|---|
| 1453 | |
|---|
| 1454 | <a name="method115"></a> |
|---|
| 1455 | <p/><strong>double ParticleDataEntry::resOpenFrac(int idSgn) </strong> <br/> |
|---|
| 1456 | calculate the fraction of the full branching ratio that is left |
|---|
| 1457 | open by the user choice of allowed decay channels. |
|---|
| 1458 | |
|---|
| 1459 | |
|---|
| 1460 | <a name="method116"></a> |
|---|
| 1461 | <p/><strong>double ParticleDataEntry::resWidthRescaleFactor() </strong> <br/> |
|---|
| 1462 | the factor used to rescale all partial widths in case the total |
|---|
| 1463 | width is being forced to a specific value by the user. |
|---|
| 1464 | |
|---|
| 1465 | |
|---|
| 1466 | <a name="method117"></a> |
|---|
| 1467 | <p/><strong>double ParticleDataEntry::resWidthChan(double mHat, int idAbs1 = 0, int idAbs2 = 0) </strong> <br/> |
|---|
| 1468 | special case to calculate one final-state width; currently only used |
|---|
| 1469 | for Higgs decay to <i>q qbar</i>, <i>g g</i> or |
|---|
| 1470 | <i>gamma gamma</i>. |
|---|
| 1471 | |
|---|
| 1472 | |
|---|
| 1473 | <h3>The DecayChannel methods</h3> |
|---|
| 1474 | |
|---|
| 1475 | The properties stored in an individual decay channel can be set or get |
|---|
| 1476 | by the methods in this section. |
|---|
| 1477 | |
|---|
| 1478 | <a name="method118"></a> |
|---|
| 1479 | <p/><strong>DecayChannel::DecayChannel(int onMode = 0, double bRatio = 0., int meMode = 0, int prod0 = 0, int prod1 = 0, int prod2 = 0, int prod3 = 0, int prod4 = 0, int prod5 = 0, int prod6 = 0, int prod7 = 0) </strong> <br/> |
|---|
| 1480 | the constructor for a decay channel. Internal. |
|---|
| 1481 | |
|---|
| 1482 | |
|---|
| 1483 | <a name="method119"></a> |
|---|
| 1484 | <p/><strong>void DecayChannel::onMode(int onMode) </strong> <br/> |
|---|
| 1485 | |
|---|
| 1486 | <strong>int DecayChannel::onMode() </strong> <br/> |
|---|
| 1487 | set or get the <code>onMode</code> of a decay channel,<br/> |
|---|
| 1488 | 0 if a channel is off,<br/> |
|---|
| 1489 | 1 if on,<br/> |
|---|
| 1490 | 2 if on for a particle but off for an antiparticle,<br/> |
|---|
| 1491 | 3 if on for an antiparticle but off for a particle.<br/> |
|---|
| 1492 | If a particle is its own antiparticle then 2 is on and 3 off |
|---|
| 1493 | but, of course, for such particles it is much simpler and safer |
|---|
| 1494 | to use only 1 and 0.<br/> |
|---|
| 1495 | The 2 and 3 options can be used e.g. to encode CP violation in |
|---|
| 1496 | B decays, or to let the <i>W</i>'s in a <i>q qbar -> W^+ W^-</i> |
|---|
| 1497 | process decay in different channels. |
|---|
| 1498 | |
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| 1499 | |
|---|
| 1500 | <a name="method120"></a> |
|---|
| 1501 | <p/><strong>void DecayChannel::bRatio(double bRatio, bool countAsChanged = true) </strong> <br/> |
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| 1502 | |
|---|
| 1503 | <strong>double DecayChannel::bRatio() </strong> <br/> |
|---|
| 1504 | set or get the branching ratio of the channel. Second argument only |
|---|
| 1505 | for internal use. |
|---|
| 1506 | |
|---|
| 1507 | |
|---|
| 1508 | <a name="method121"></a> |
|---|
| 1509 | <p/><strong>void DecayChannel::rescaleBR(double fac) </strong> <br/> |
|---|
| 1510 | multiply the current branching ratio by <code>fac</code>. |
|---|
| 1511 | |
|---|
| 1512 | |
|---|
| 1513 | <a name="method122"></a> |
|---|
| 1514 | <p/><strong>void DecayChannel::meMode(int meMode) </strong> <br/> |
|---|
| 1515 | |
|---|
| 1516 | <strong>int DecayChannel::meMode() </strong> <br/> |
|---|
| 1517 | set or get the mode of processing this channel, possibly with matrix |
|---|
| 1518 | elements (see the <a href="ParticleDecays.html" target="page">particle decays</a> |
|---|
| 1519 | description). |
|---|
| 1520 | |
|---|
| 1521 | |
|---|
| 1522 | <a name="method123"></a> |
|---|
| 1523 | <p/><strong>void DecayChannel::multiplicity(int multiplicity) </strong> <br/> |
|---|
| 1524 | |
|---|
| 1525 | <strong>int DecayChannel::multiplicity() </strong> <br/> |
|---|
| 1526 | set or get the number of decay products in a channel, at most 8. |
|---|
| 1527 | (Is normally not to be set by hand, since it is automatically |
|---|
| 1528 | updated whenever the products list is changed.) |
|---|
| 1529 | |
|---|
| 1530 | |
|---|
| 1531 | <a name="method124"></a> |
|---|
| 1532 | <p/><strong>void DecayChannel::product(int i, int product) </strong> <br/> |
|---|
| 1533 | |
|---|
| 1534 | <strong>int DecayChannel::product(int i) </strong> <br/> |
|---|
| 1535 | set or get a list of the decay products, 8 products 0 <= i < 8, |
|---|
| 1536 | with trailing unused ones set to 0. |
|---|
| 1537 | |
|---|
| 1538 | |
|---|
| 1539 | <a name="method125"></a> |
|---|
| 1540 | <p/><strong>void DecayChannel::setHasChanged(bool hasChanged) </strong> <br/> |
|---|
| 1541 | |
|---|
| 1542 | <strong>bool DecayChannel::hasChanged() </strong> <br/> |
|---|
| 1543 | used for internal purposes, to know which decay modes have been changed. |
|---|
| 1544 | |
|---|
| 1545 | |
|---|
| 1546 | <a name="method126"></a> |
|---|
| 1547 | <p/><strong>bool DecayChannel::contains(int id1) </strong> <br/> |
|---|
| 1548 | |
|---|
| 1549 | <strong>bool DecayChannel::contains(int id1, int id2) </strong> <br/> |
|---|
| 1550 | |
|---|
| 1551 | <strong>bool DecayChannel::contains(int id1, int id2, int id3) </strong> <br/> |
|---|
| 1552 | find if the decay product list contains the one, two or three particle |
|---|
| 1553 | identities provided. If the same code is repeated then so must it be in |
|---|
| 1554 | the products list. Matching also requires correct sign. |
|---|
| 1555 | |
|---|
| 1556 | |
|---|
| 1557 | <a name="method127"></a> |
|---|
| 1558 | <p/><strong>void DecayChannel::currentBR(double currentBR) </strong> <br/> |
|---|
| 1559 | |
|---|
| 1560 | <strong>double DecayChannel::currentBR() </strong> <br/> |
|---|
| 1561 | set or get the current branching ratio, taking into account on/off |
|---|
| 1562 | switches and dynamic width for resonances. For internal use. |
|---|
| 1563 | |
|---|
| 1564 | |
|---|
| 1565 | <a name="method128"></a> |
|---|
| 1566 | <p/><strong>void DecayChannel::onShellWidth(double onShellWidth) </strong> <br/> |
|---|
| 1567 | |
|---|
| 1568 | <strong>double DecayChannel::onShellWidth() </strong> <br/> |
|---|
| 1569 | set or get the current partial width of the channel; intended for |
|---|
| 1570 | resonances where the widhts are recalculated based on the current |
|---|
| 1571 | resonance mass. For internal use. |
|---|
| 1572 | |
|---|
| 1573 | |
|---|
| 1574 | <a name="method129"></a> |
|---|
| 1575 | <p/><strong>void DecayChannel::onShellWidthFactor(double factor) </strong> <br/> |
|---|
| 1576 | multiply the current partial width by <code>factor</code>. |
|---|
| 1577 | |
|---|
| 1578 | |
|---|
| 1579 | <a name="method130"></a> |
|---|
| 1580 | <p/><strong>void DecayChannel::openSec(int idSgn, double openSecIn) </strong> <br/> |
|---|
| 1581 | |
|---|
| 1582 | <strong>double DecayChannel::openSec(nt idSgn) </strong> <br/> |
|---|
| 1583 | set or get the fraction of secondary open widths, separately for |
|---|
| 1584 | positive and negative particles. For internal use. |
|---|
| 1585 | |
|---|
| 1586 | |
|---|
| 1587 | </body> |
|---|
| 1588 | </html> |
|---|
| 1589 | |
|---|
| 1590 | <!-- Copyright (C) 2012 Torbjorn Sjostrand --> |
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