[1] | 1 | <html> |
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| 2 | <head> |
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| 3 | <title>Left-Right-Symmetry Processes</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>Left-Right-Symmetry Processes</h2> |
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| 10 | |
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| 11 | At current energies, the world is left-handed, i.e. the Standard Model |
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| 12 | contains an <i>SU(2)_L</i> group. Left-right symmetry at some larger |
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| 13 | scale implies the need for an <i>SU(2)_R</i> group. Thus the particle |
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| 14 | content is expanded by right-handed <i>Z_R^0</i> and <i>W_R^+-</i> |
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| 15 | and right-handed neutrinos. The Higgs fields have to be in a triplet |
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| 16 | representation, leading to doubly-charged Higgs particles, one set for |
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| 17 | each of the two <i>SU(2)</i> groups. Also the number of neutral and |
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| 18 | singly-charged Higgs states is increased relative to the Standard Model, |
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| 19 | but a search for the lowest-lying states of this kind is no different |
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| 20 | from e.g. the freedom already accorded by the MSSM Higgs scenarios. |
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| 21 | |
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| 22 | <p/> |
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| 23 | PYTHIA implements the scenario of [<a href="Bibliography.html" target="page">Hui97</a>]. |
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| 24 | |
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| 25 | <p/> |
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| 26 | The <i>W_R^+-</i> has been implemented as a simple copy of the |
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| 27 | ordinary <i>W^+-</i>, with the exception that it couples to |
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| 28 | right-handed neutrinos instead of the ordinary left-handed ones. |
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| 29 | Thus the standard CKM matrix is used in the quark sector, and the |
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| 30 | same vector and axial coupling strengths, leaving only the mass as |
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| 31 | free parameter. The <i>Z_R^0</i> implementation (without interference |
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| 32 | with the photon or the ordinary <i>Z^0</i>) allows decays both to |
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| 33 | left- and right-handed neutrinos, as well as other fermions, according |
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| 34 | to one specific model ansatz. Obviously both the <i>W_R^+-</i> |
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| 35 | and the <i>Z_R^0</i> descriptions are likely to be simplifications, |
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| 36 | but provide a starting point. |
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| 37 | |
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| 38 | <p/> |
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| 39 | For the doubly-charged Higgses, the main decay modes implemented are |
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| 40 | <i>H_L^++ -> W_L^+ W_L^+, l_i^+ l_j^+ </i> (<i>i, j</i> generation |
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| 41 | indices) and <i>H_R^++ -> W_R^+ W_R^+, l_i^+ l_j^+</i>. |
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| 42 | |
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| 43 | <p/> |
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| 44 | The right-handed neutrinos can be allowed to decay further. Assuming them |
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| 45 | to have a mass below that of <i>W_R^+-</i>, they decay to three-body |
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| 46 | states via a virtual <i>W_R^+-</i>, <i>nu_Rl -> l+- f fbar'</i>, |
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| 47 | where both lepton charges are allowed owing to the Majorana character |
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| 48 | of the neutrinos. If there is a significant mass splitting, also |
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| 49 | sequential decays <i>nu_Rl -> l+- l'-+ nu'_Rl</i> are allowed. |
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| 50 | Currently the decays are isotropic in phase space. If the neutrino |
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| 51 | masses are close to or above the <i>W_R^</i> ones, this description |
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| 52 | has to be substituted by a sequential decay via a real <i>W_R^</i> |
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| 53 | (not implemented, but actually simpler to do than the one here). |
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| 54 | |
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| 55 | |
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| 56 | <h3>Production processes</h3> |
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| 57 | |
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| 58 | A few different production processes have been implemented, which normally |
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| 59 | would not overlap and therefore could be run together. |
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| 60 | |
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| 61 | <p/><code>flag </code><strong> LeftRightSymmmetry:all </strong> |
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| 62 | (<code>default = <strong>off</strong></code>)<br/> |
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| 63 | Common switch for the group of implemented processes within a |
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| 64 | left-right-symmetric scenario. |
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| 65 | |
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| 66 | |
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| 67 | <p/><code>flag </code><strong> LeftRightSymmmetry:ffbar2ZR </strong> |
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| 68 | (<code>default = <strong>off</strong></code>)<br/> |
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| 69 | Scatterings <i>f fbar -> Z_R^0</i>. |
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| 70 | Code 3101. |
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| 71 | |
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| 72 | |
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| 73 | <p/><code>flag </code><strong> LeftRightSymmmetry:ffbar2WR </strong> |
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| 74 | (<code>default = <strong>off</strong></code>)<br/> |
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| 75 | Scatterings <i><f fbar' -> W_R^+</i>. |
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| 76 | Code 3102. |
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| 77 | |
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| 78 | |
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| 79 | <p/><code>flag </code><strong> LeftRightSymmmetry:ll2HL </strong> |
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| 80 | (<code>default = <strong>off</strong></code>)<br/> |
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| 81 | Scatterings <i>l_i l_j -> H_L^--</i>. |
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| 82 | Code 3121. |
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| 83 | |
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| 84 | |
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| 85 | <p/><code>flag </code><strong> LeftRightSymmmetry:lgm2HLe </strong> |
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| 86 | (<code>default = <strong>off</strong></code>)<br/> |
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| 87 | Scatterings <i>l_i gamma -> H_L^-- e^+</i>. |
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| 88 | Code 3122. |
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| 89 | |
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| 90 | |
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| 91 | <p/><code>flag </code><strong> LeftRightSymmmetry:lgm2HLmu </strong> |
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| 92 | (<code>default = <strong>off</strong></code>)<br/> |
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| 93 | Scatterings <i>l_i gamma -> H_L^-- mu^+</i>. |
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| 94 | Code 3123. |
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| 95 | |
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| 96 | |
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| 97 | <p/><code>flag </code><strong> LeftRightSymmmetry:lgm2HLtau </strong> |
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| 98 | (<code>default = <strong>off</strong></code>)<br/> |
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| 99 | Scatterings <i>l_i gamma -> H_L^-- tau^+</i>. |
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| 100 | Code 3124. |
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| 101 | |
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| 102 | |
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| 103 | <p/><code>flag </code><strong> LeftRightSymmmetry:ff2HLff </strong> |
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| 104 | (<code>default = <strong>off</strong></code>)<br/> |
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| 105 | Scatterings <i>f_1 f_2 -> H_L^-- f_3 f_4</i> via <i>WW</i> fusion. |
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| 106 | Code 3125. |
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| 107 | |
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| 108 | |
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| 109 | <p/><code>flag </code><strong> LeftRightSymmmetry:ffbar2HLHL </strong> |
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| 110 | (<code>default = <strong>off</strong></code>)<br/> |
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| 111 | Scatterings <i>f fbar -> H_L^++ H_L^--</i>. |
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| 112 | Code 3126. |
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| 113 | |
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| 114 | |
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| 115 | <p/><code>flag </code><strong> LeftRightSymmmetry:ll2HR </strong> |
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| 116 | (<code>default = <strong>off</strong></code>)<br/> |
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| 117 | Scatterings <i>l_i l_j -> H_R^--</i>. |
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| 118 | Code 3141. |
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| 119 | |
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| 120 | |
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| 121 | <p/><code>flag </code><strong> LeftRightSymmmetry:lgm2HRe </strong> |
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| 122 | (<code>default = <strong>off</strong></code>)<br/> |
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| 123 | Scatterings <i>l_i gamma -> H_R^-- e^+</i>. |
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| 124 | Code 3142. |
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| 125 | |
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| 126 | |
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| 127 | <p/><code>flag </code><strong> LeftRightSymmmetry:lgm2HRmu </strong> |
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| 128 | (<code>default = <strong>off</strong></code>)<br/> |
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| 129 | Scatterings <i>l_i gamma -> H_R^-- mu^+</i>. |
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| 130 | Code 3143. |
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| 131 | |
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| 132 | |
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| 133 | <p/><code>flag </code><strong> LeftRightSymmmetry:lgm2HRtau </strong> |
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| 134 | (<code>default = <strong>off</strong></code>)<br/> |
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| 135 | Scatterings <i>l_i gamma -> H_R^-- tau^+</i>. |
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| 136 | Code 3144. |
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| 137 | |
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| 138 | |
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| 139 | <p/><code>flag </code><strong> LeftRightSymmmetry:ff2HRff </strong> |
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| 140 | (<code>default = <strong>off</strong></code>)<br/> |
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| 141 | Scatterings <i>f_1 f_2 -> H_R^-- f_3 f_4</i> via <i>WW</i> fusion. |
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| 142 | Code 3145. |
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| 143 | |
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| 144 | |
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| 145 | <p/><code>flag </code><strong> LeftRightSymmmetry:ffbar2HRHR </strong> |
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| 146 | (<code>default = <strong>off</strong></code>)<br/> |
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| 147 | Scatterings <i>f fbar -> H_R^++ H_L^--</i>. |
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| 148 | Code 3146. |
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| 149 | |
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| 150 | |
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| 151 | <h3>Parameters</h3> |
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| 152 | |
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| 153 | The basic couplings of the model are |
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| 154 | |
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| 155 | <p/><code>parm </code><strong> LeftRightSymmmetry:gL </strong> |
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| 156 | (<code>default = <strong>0.64</strong></code>; <code>minimum = 0.0</code>)<br/> |
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| 157 | lefthanded coupling <i>g_L = e / sin(theta)</i>. |
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| 158 | |
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| 159 | |
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| 160 | <p/><code>parm </code><strong> LeftRightSymmmetry:gR </strong> |
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| 161 | (<code>default = <strong>0.64</strong></code>; <code>minimum = 0.0</code>)<br/> |
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| 162 | righthanded coupling <i>g_R</i>, assumed the same as <i>g_L</i>. |
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| 163 | |
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| 164 | |
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| 165 | <p/><code>parm </code><strong> LeftRightSymmmetry:vL </strong> |
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| 166 | (<code>default = <strong>5.</strong></code>; <code>minimum = 0.0</code>)<br/> |
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| 167 | vacuum expectation value <i>v_L</i> (in GeV) for the left-triplet. |
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| 168 | |
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| 169 | |
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| 170 | <p/> |
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| 171 | The corresponding vacuum expectation value <i>v_R</i> is assumed |
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| 172 | given by <i>v_R = sqrt(2) M_WR / g_R</i> and is not stored explicitly. |
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| 173 | |
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| 174 | <p/> |
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| 175 | The Yukawa couplings of a lepton pair to a <i>H^--</i>, assumed the |
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| 176 | same for <i>H_L^--</i> and <i>H_R^--</i>, is described by a symmetric |
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| 177 | 3-by-3 matrix. The default matrix is dominated by the diagonal elements |
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| 178 | and especially by the <i>tau tau</i> one. |
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| 179 | |
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| 180 | <p/><code>parm </code><strong> LeftRightSymmmetry:coupHee </strong> |
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| 181 | (<code>default = <strong>0.1</strong></code>; <code>minimum = 0.0</code>)<br/> |
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| 182 | Yukawa coupling for <i>H^-- -> e- e-</i>. |
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| 183 | |
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| 184 | |
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| 185 | <p/><code>parm </code><strong> LeftRightSymmmetry:coupHmue </strong> |
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| 186 | (<code>default = <strong>0.01</strong></code>; <code>minimum = 0.0</code>)<br/> |
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| 187 | Yukawa coupling for <i>H^-- -> mu- e-</i>. |
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| 188 | |
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| 189 | |
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| 190 | <p/><code>parm </code><strong> LeftRightSymmmetry:coupHmumu </strong> |
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| 191 | (<code>default = <strong>0.1</strong></code>; <code>minimum = 0.0</code>)<br/> |
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| 192 | Yukawa coupling for <i>H^-- -> mu- mu-</i>. |
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| 193 | |
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| 194 | |
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| 195 | <p/><code>parm </code><strong> LeftRightSymmmetry:coupHtaue </strong> |
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| 196 | (<code>default = <strong>0.01</strong></code>; <code>minimum = 0.0</code>)<br/> |
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| 197 | Yukawa coupling for <i>H^-- -> tau- e-</i>. |
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| 198 | |
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| 199 | |
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| 200 | <p/><code>parm </code><strong> LeftRightSymmmetry:coupHtaumu </strong> |
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| 201 | (<code>default = <strong>0.01</strong></code>; <code>minimum = 0.0</code>)<br/> |
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| 202 | Yukawa coupling for <i>H^-- -> tau- mu-</i>. |
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| 203 | |
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| 204 | |
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| 205 | <p/><code>parm </code><strong> LeftRightSymmmetry:coupHtautau </strong> |
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| 206 | (<code>default = <strong>0.3</strong></code>; <code>minimum = 0.0</code>)<br/> |
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| 207 | Yukawa coupling for <i>H^-- -> tau- tau-</i>. |
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| 208 | |
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| 209 | |
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| 210 | </body> |
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| 211 | </html> |
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| 212 | |
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| 213 | <!-- Copyright (C) 2012 Torbjorn Sjostrand --> |
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| 214 | |
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