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1<html>
2<head>
3<title>R-hadrons</title>
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28<form method='post' action='RHadrons.php'>
29
30<h2>R-hadrons</h2>
31
32When a coloured SUSY particle is longer-lived than typical
33hadronization scales, i.e. around c*tau > 1 fm, or equivalently
34width Gamma < 0.2 GeV, it will have time to hadronize into a colour
35singlet hadronic state, a R-hadron. Currently a set of such
36R-hadrons have been implemented for the case of a long-lived
37gluino, stop or sbottom. Needless to say, the normal case would be
38that only one of them will be long-lived enough to form R-hadrons.
39
40<p/>
41For simplicity all gluino-mesons are assumed to have light-flavour
42spin 1, since those are the lightest and favoured by spin-state
43counting. Further, all gluino-baryons are bookkept as having
44light-flavour spin 3/2, and flavours are listed in descending order.
45This is more for convenience of notation, however, since the normal
46baryon octet e.g. has no uuu = "p++" state. When a diquark is
47extracted, a mixture of spin 0 and spin 1 is allowed. Names and codes
48are essentially in agreement with the PDG conventions, e.g. 
49<br/>1000993 <code>R0(~g g)</code> (or gluinoball)
50<br/>1009213 <code>R+(~g u dbar)</code> (or gluino-rho+)
51<br/>1092214 <code>R+(~g uud)</code> (or gluino-Delta+)
52<br/>For internal bookkeeping of momenta, the code 1009002,
53<code>Rtemp(~g q)</code>, is used to denote the intermediate
54state formed when only one of the two string peices attached to
55the gluino has broken.
56
57<p/>
58For the stop- and sbottom-hadrons the spin counting is simpler,
59since it is entirely given by the constituent quark or diquark spin.
60Again names and codes follow PDG conventions, e.g.
61<br/>1000612 <code>R+(~t dbar)</code> 
62<br/>1006211 <code>R+(~t ud0)</code> 
63
64<p/>
65The spin and electromagnetic charge of the new particle plays only
66a minor role in the hadronization process, that can be neglected
67to first approximation. Therefore it is possible to use the same
68R-hadrons framework instead for other BSM scenarios with long-lived
69coloured particles, e.g. with massive extra-dimensions copies
70of gluons and quarks, or with leptoquarks. This can be regulated by
71the switches below. Note that the codes and names of the R-hadrons
72is not changed when the heavy particle involved is switched, for
73reasons of administrative simplicity. R-hadron mass spectra and
74other relevant particle data is automatically updated to reflect
75the change, however.
76
77<br/><br/><strong>RHadrons:allow</strong>  <input type="radio" name="1" value="on"><strong>On</strong>
78<input type="radio" name="1" value="off" checked="checked"><strong>Off</strong>
79 &nbsp;&nbsp;(<code>default = <strong>off</strong></code>)<br/>
80Allows the gluino, stop and sbottom to hadronize if their respective
81widths are below the limit <code>RHadrons:maxWidth</code>.
82 
83
84<br/><br/><table><tr><td><strong>RHadrons:maxWidth </td><td></td><td> <input type="text" name="2" value="0.2" size="20"/>  &nbsp;&nbsp;(<code>default = <strong>0.2</strong></code>; <code>minimum = 0.0</code>; <code>maximum = 1.0</code>)</td></tr></table>
85The maximum width of the gluino for which it is possible to form
86R-hadrons, provided that <code>RHadrons:allow</code> is on.
87 
88
89<p/><code>mode&nbsp; </code><strong> RHadrons:idGluino &nbsp;</strong>
90 (<code>default = <strong>1000021</strong></code>)<br/>
91The gluino identity code. For other scenarios than SUSY this code
92could be changed to represent another long-lived uncharged colour
93octet particle, that then would be treated in the same spirit.
94Could be set to 0 to forbid any gluino R-hadron formation even when
95the above two criteria, <code>RHadrons:allow</code>
96and <code>RHadrons:maxWidth</code>, are met.
97 
98
99<p/><code>mode&nbsp; </code><strong> RHadrons:idStop &nbsp;</strong>
100 (<code>default = <strong>1000006</strong></code>)<br/>
101The lightest stop identity code. For other scenarios than SUSY this
102code could be changed to represent another long-lived charge 2/3
103colour triplet particle, that then would be treated in the same
104spirit. As above it could be set to 0 to forbid any stop R-hadron
105formation.
106 
107
108<p/><code>mode&nbsp; </code><strong> RHadrons:idSbottom &nbsp;</strong>
109 (<code>default = <strong>1000005</strong></code>)<br/>
110The lightest sbottom identity code. For other scenarios than SUSY this
111code could be changed to represent another long-lived charge -1/3
112colour triplet particle, that then would be treated in the same
113spirit. As above it could be set to 0 to forbid any sbottom R-hadron
114formation.
115 
116
117<br/><br/><strong>RHadrons:allowDecay</strong>  <input type="radio" name="3" value="on" checked="checked"><strong>On</strong>
118<input type="radio" name="3" value="off"><strong>Off</strong>
119 &nbsp;&nbsp;(<code>default = <strong>on</strong></code>)<br/>
120Allows the R-hadrons to decay or not. If the gluino/stop/sbottom is
121stable or too long-lived to decay inside the detector this switch
122has no real function, since then no decays will be performed anyway.
123If the sparticle is so short-lived that it decays before reaching
124the beam pipe then having the decay on is the logical choice.
125So the interesting region is when the decays happens after the
126R-hadron has passed through part of the detector, and changed its
127momentum and quite possibly its flavour content before it is to
128decay. Then normal decays should be switched off, and the R-hadron
129tracked through matter by a program like GEANT
130[<a href="Bibliography.php" target="page">Kra04,Mac07</a>]. After that, the new R-hadron info can be
131overwritten into the event record and the
132<code>Pythia::forceRHadronDecay()</code> method can be called
133to force this modified R-hadron to decay.
134 
135
136<br/><br/><strong>RHadrons:setMasses</strong>  <input type="radio" name="4" value="on" checked="checked"><strong>On</strong>
137<input type="radio" name="4" value="off"><strong>Off</strong>
138 &nbsp;&nbsp;(<code>default = <strong>on</strong></code>)<br/>
139Use simple mass formulae to construct all available R-hadron masses
140based on the currently initialized gluino/squark masses and the
141constituent masses of the other partons in the hadron. If you switch
142this off, it is your responsibility to set each of the R-hadron masses
143on your own, and set them in an internally consistent way. If you
144mess up on this you may generate accordingly crazy results.
145Specifically, it is to be assumed that none of the R-hadrons has a
146mass below its constituent sparticle, i.e. that the light degrees
147of freedom and the additional confinement gluon field gives a net
148positive contribution to the R-hadron mass.
149 
150
151<br/><br/><table><tr><td><strong>RHadrons:probGluinoball </td><td></td><td> <input type="text" name="5" value="0.1" size="20"/>  &nbsp;&nbsp;(<code>default = <strong>0.1</strong></code>; <code>minimum = 0.0</code>; <code>maximum = 1.0</code>)</td></tr></table>
152The fraction of produced gluino R-hadrons that are contain a "valence"
153gluon, with the rest containing a meson or baryon quark flavour content.
154 
155
156<br/><br/><table><tr><td><strong>RHadrons:mOffsetCloud </td><td></td><td> <input type="text" name="6" value="0.2" size="20"/>  &nbsp;&nbsp;(<code>default = <strong>0.2</strong></code>; <code>minimum = 0.0</code>)</td></tr></table>
157Extra mass (in GeV) added to each of the one or two extra constituent
158masses in an R-hadron, to calculate the mass of a R-hadron. The same
159offset is also used when the R-hadron momentum and mass is split
160between the squark or gluino and the one or two light (di)quarks,
161one for a squark and two for a gluino. Thus once or twice this amount
162represents a part of the nominal squark or gluino mass that will not
163decay weakly, since it is taken to correspond to the cloud of gluons
164that surround the squark or gluino.
165 
166
167<br/><br/><table><tr><td><strong>RHadrons:mCollapse </td><td></td><td> <input type="text" name="7" value="1.0" size="20"/>  &nbsp;&nbsp;(<code>default = <strong>1.0</strong></code>; <code>minimum = 0.0</code>)</td></tr></table>
168A colour singlet system with an invariant mass less than this amount,
169above the R-hadron mass with the given flavour content, is assumed to
170collapse to this single R-hadron, whereas a full fragmentation handling
171is applied above this mass.
172 
173
174<br/><br/><table><tr><td><strong>RHadrons:diquarkSpin1 </td><td></td><td> <input type="text" name="8" value="0.5" size="20"/>  &nbsp;&nbsp;(<code>default = <strong>0.5</strong></code>; <code>minimum = 0.0</code>; <code>maximum = 1.0</code>)</td></tr></table>
175Probability that a diquark extracted from the flavour code of a gluino
176R-hadron should be assigned spin 1, with the rest being spin 0. Does
177not apply for two identical quarks, where spin 1 is only possibility.
178Note that gluino R-hadron codes for simplicity are assigned as if spin
179is 1 always, and so give no guidance. For stop and sbottom the diquark
180spin is preserved in the particle code, so there is no corresponding
181issue.
182 
183
184<input type="hidden" name="saved" value="1"/>
185
186<?php
187echo "<input type='hidden' name='filepath' value='".$_GET["filepath"]."'/>"?>
188
189<table width="100%"><tr><td align="right"><input type="submit" value="Save Settings" /></td></tr></table>
190</form>
191
192<?php
193
194if($_POST["saved"] == 1)
195{
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197$handle = fopen($filepath, 'a');
198
199if($_POST["1"] != "off")
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209if($_POST["3"] != "on")
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214if($_POST["4"] != "on")
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216$data = "RHadrons:setMasses = ".$_POST["4"]."\n";
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224if($_POST["6"] != "0.2")
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226$data = "RHadrons:mOffsetCloud = ".$_POST["6"]."\n";
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234if($_POST["8"] != "0.5")
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237fwrite($handle,$data);
238}
239fclose($handle);
240}
241
242?>
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