3 <title>SUSY Processes</title>
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30 <h2>SUSY Processes</h2>
32 The implementation of SUSY processes was only recently completed, and
33 hence case-by-case validations against other codes are still
34 recommended. In all cases, a set of default validations have already been
35 carried out by the authors. These validations compared to the PYTHIA 6
36 SUSY implementation, using an sps1a spectrum. Most of the
37 SLHA2-specific extensions have not been explicitly validated,
38 however, with the exception of the R-parity violating single-sparticle
39 production cross sections.
42 Here is collected processes involving supersymmetric particle
43 production, with the exception of the (extended) Higgs sector.
44 Since the number of separate but closely related processes is so big,
45 there will not be switches for each separate process but only for a
46 reasonable set of subgroups. However, the general
47 switches <code>SUSY:idA</code> and <code>SUSY:idB</code> may be used in
48 conjunction with any of these groups to provide some additional
49 flexibility to concentrate on processes involving only specific (s)particle
50 final states, see below.
52 <br/><br/><b>Important note:</b>
53 In order to simulate SUSY processes it is required to read in the
54 couplings and masses relevant for the scenario to be studied. This
55 is done with the help of the SUSY Les Houches Accord (SLHA), including
56 the SLHA2 extensions and generalizations. (Internally, the SLHA2
57 conventions are used. SLHA1 spectra are automatically translated into
58 SLHA2 notation during initialization.) The
59 reading of a relevant SLHA file <b>must</b> be set up, as described
60 on <?php $filepath = $_GET["filepath"];
61 echo "<a href='SUSYLesHouchesAccord.php?filepath=".$filepath."' target='page'>";?>the SLHA page</a>.
64 Note also that lepton- and photon-initial states are not yet available.
65 Only quark/gluon-initiated <i>2 -> 2</i> and <i>2 -> 1</i> (RPV)
66 processes have been implemented. Likewise, direct slepton production
67 has not yet been implemented (i.e., <i>2 -> 2</i> processes
68 involving sleptons in the final state). Sleptons will of course still be
69 produced through cascade decays of heavier (s)particles.
72 Finally, note that these cross sections will be correctly folded with open
73 branching fractions of cascade decays, but at present any difference between
74 particle and antiparticle decay tables is not taken into account. This
75 possibility will be included in a future update.
77 <br/><br/><strong>SUSY:all</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 (<code>default = <strong>off</strong></code>)<br/>
80 Common switch for production of supersymmetric particles, i.e.
81 particles with R-parity -1.
84 <br/><br/><table><tr><td><strong>SUSY:idA </td><td></td><td> <input type="text" name="2" value="0" size="20"/> (<code>default = <strong>0</strong></code>; <code>minimum = 0</code>)</td></tr></table>
85 Option to limit the sum over possible outgoing states in SUSY
86 <i>2 -> 2</i> processes to ones including a specific particle
87 identity code. The default corresponds to summing over all possible
88 indices. A non-zero value of <code>SUSY:idA</code> selects only processes
89 that contain the state corresponding to that particular particle identity
90 code in the fundamental <i>2 -> 2</i> scattering process (symmetrized
91 over particle/antiparticle). It is the user's responsibility to ensure
92 that (a subset of) the processes be to simulated actually include this
93 particle at the <i>2 -> 2</i> level; thus, asking for the lightest
94 neutralino (code 1000021) to be present in a squark-squark production
95 process will give no match.
98 <br/><br/><table><tr><td><strong>SUSY:idB </td><td></td><td> <input type="text" name="3" value="0" size="20"/> (<code>default = <strong>0</strong></code>; <code>minimum = 0</code>)</td></tr></table>
99 As for <code>SUSY:idA</code>, but requires an additional particle
100 with PDG code <code>SUSY:idB</code> to be present in the <i>2 -> 2</i>
101 process. Thus, using <code>SUSY:idA</code> and <code>SUSY:idB</code>
102 a specific subprocess can be selected. Again only the absolute sign is
103 used, i.e. the summation over particle and antiparticle is retained.
106 <br/><br/><table><tr><td><strong>SUSY:sin2thetaWMode </td><td> (<code>default = <strong>2</strong></code>; <code>minimum = 1</code>; <code>maximum = 3</code>)</td></tr></table>
107 The value of <ei>sin2(thetaW)</ei> should be taken from
109 <input type="radio" name="4" value="1"><strong>1 </strong>: SM value, defined at <ei>M_Z</ei>, taken from PYTHIA's <code>StandardModel:sin2thetaW</code> parameter.<br/>
110 <input type="radio" name="4" value="2" checked="checked"><strong>2 </strong>: SUSY value, defined at <ei>M_SUSY</ei>, derived from the running gauge couplings in <code>BLOCK GAUGE</code> in the SLHA file. Note: if no such block is present in the input file, this option will default back to option 1 above, i.e., the SM value.<br/>
111 <input type="radio" name="4" value="3"><strong>3 </strong>: Pole value, defined by <ei>1 - M_W^2/M_Z^2</ei>, using the pole masses stored in the SLHA <code>BLOCK MASS</code>, or, alternatively, PYTHIA's internal pole masses if no such block is present.<br/>
113 <h3>Gluino Pair Production</h3>
115 <br/><br/><strong>SUSY:gg2gluinogluino</strong> <input type="radio" name="5" value="on"><strong>On</strong>
116 <input type="radio" name="5" value="off" checked="checked"><strong>Off</strong>
117 (<code>default = <strong>off</strong></code>)<br/>
118 Pair production of gluinos by gluon-gluon initial states.
121 <br/><br/><strong>SUSY:qqbar2gluinogluino</strong> <input type="radio" name="6" value="on"><strong>On</strong>
122 <input type="radio" name="6" value="off" checked="checked"><strong>Off</strong>
123 (<code>default = <strong>off</strong></code>)<br/>
124 Pair production of gluinos by quark-antiquark annihilation and
125 <i>t</i>-channel squark exchange. So far, these cross sections assume the
126 squark CKM is aligned with the quark CKM and that all quantities are
127 real, so effects of non-minimal flavour violation and/or CP violation
128 are not yet included.
131 <h3>Associated Squark-Gluino Production</h3>
133 <br/><br/><strong>SUSY:qg2squarkgluino</strong> <input type="radio" name="7" value="on"><strong>On</strong>
134 <input type="radio" name="7" value="off" checked="checked"><strong>Off</strong>
135 (<code>default = <strong>off</strong></code>)<br/>
136 Associated production of a squark with a gluino. Only implemented for the
137 flavor-diagonal case. So far, these cross sections assume the
138 squark CKM is aligned with the quark CKM and that all quantities are
139 real, so effects of non-minimal flavour violation and/or CP violation
140 are not yet included.
143 <h3>Squark Pair Production</h3>
145 <br/><br/><strong>SUSY:gg2squarkantisquark</strong> <input type="radio" name="8" value="on"><strong>On</strong>
146 <input type="radio" name="8" value="off" checked="checked"><strong>Off</strong>
147 (<code>default = <strong>off</strong></code>)<br/>
148 Pair production of a scalar quark together with a scalar antiquark by
149 gluon annhilation via <i>s</i>-channel gluon exhange, <i>t</i>- and
150 <i>u</i>-channel squark exchange, and the direct 4-point coupling.
151 The cross section expression follows [<a href="Bibliography.php" target="page">Boz07</a>].
152 Validation of the FLV and CPV cases has not yet been completed.
155 <br/><br/><strong>SUSY:qqbar2squarkantisquark</strong> <input type="radio" name="9" value="on"><strong>On</strong>
156 <input type="radio" name="9" value="off" checked="checked"><strong>Off</strong>
157 (<code>default = <strong>off</strong></code>)<br/>
158 Pair production of a scalar quark together with a scalar antiquark
159 by quark-antiquark annihilation.
160 For same-isospin <i>~q~q*</i> production (i.e., <i>~u~u*</i>,
161 <i>~u~c*</i>, ...), the <i>s</i>-channel gluon, photon, and
162 <i>Z</i> and <i>t</i>-channel gluino contributions have so far
163 been implemented (i.e., the <i>t</i>-channel neutralino contributions
164 are neglected). For opposite-isospin <i>~q~q*</i> production
165 (<i>~u~d*</i>, <i>~u~s*</i>, ...), the <i>s</i>-channel <i>W</i>
166 and <i>t</i>-channel gluino contributions have been implemented
167 (i.e., the <i>t</i>-channel neutralino contributions are neglected).
168 The cross section expressions follow [<a href="Bibliography.php" target="page">Boz07</a>].
169 Validation of the FLV and CPV cases has not yet been completed.
170 (Note to PYTHIA 6 users:
171 in older PYTHIA 6 versions, a bug caused the <i>~t1~t2*</i> cross to be
172 overcounted by a factor of 2. Starting from version 6.4.24, that
173 generator now agrees with the implementation here.)
176 <br/><br/><strong>SUSY:qqbar2squarkantisquark:onlyQCD</strong> <input type="radio" name="10" value="on"><strong>On</strong>
177 <input type="radio" name="10" value="off" checked="checked"><strong>Off</strong>
178 (<code>default = <strong>off</strong></code>)<br/>
179 When switched <code>on</code> this flag switches off all but the
180 <i>s</i>-channel gluon contribution in the
181 calculation of same-isospin squark-antisquark production cross
182 sections. Intended for reference only. For the most
183 accurate physics simulation, leave this flag in the <code>off</code>
187 <br/><br/><strong>SUSY:qq2squarksquark</strong> <input type="radio" name="11" value="on"><strong>On</strong>
188 <input type="radio" name="11" value="off" checked="checked"><strong>Off</strong>
189 (<code>default = <strong>off</strong></code>)<br/>
190 Pair production of scalar quarks (squark-squark and its charge
191 conjugate process; for squark-antisquark production see above)
192 by <i>t</i>- and <i>u</i>-channel gluino, neutralino, and
193 chargino exchange. The cross section expressions follow [<a href="Bibliography.php" target="page">Boz07</a>].
194 Validation of the FLV and CPV cases has not yet been completed.
195 (Note to PYTHIA 6 users: PYTHIA 6 only included the gluino exchange
196 contribution, which typically dominates due to the size of the strong
197 coupling; for counterchecks,
198 the flag <code>SUSY:qq2squarksquark:onlyQCD</code>
199 below can be switched on to eliminate the chargino and neutralino
203 <br/><br/><strong>SUSY:qq2squarksquark:onlyQCD</strong> <input type="radio" name="12" value="on"><strong>On</strong>
204 <input type="radio" name="12" value="off" checked="checked"><strong>Off</strong>
205 (<code>default = <strong>off</strong></code>)<br/>
206 When switched <code>on</code> this flag causes the <i>t</i>- or
207 <i>u</i>-channel neutralino and chargino contributions to be
208 ignored in the calculation of squark pair production cross sections.
209 Intended for reference only. For the most accurate physics simulation,
210 leave this flag in the <code>off</code> position.
213 <h3>Neutralino and Chargino Pair Production</h3>
215 <br/><br/><strong>SUSY:qqbar2chi0chi0</strong> <input type="radio" name="13" value="on"><strong>On</strong>
216 <input type="radio" name="13" value="off" checked="checked"><strong>Off</strong>
217 (<code>default = <strong>off</strong></code>)<br/>
218 Pair production of neutralinos by quark-antiquark annihilation. With
219 four neutralino species this gives ten separate processes, codes
220 1201 - 1210. The cross section expressions follow [<a href="Bibliography.php" target="page">Boz07</a>].
221 Validation of the FLV and CPV cases has not yet been completed.
224 <br/><br/><strong>SUSY:qqbar2chi+-chi0</strong> <input type="radio" name="14" value="on"><strong>On</strong>
225 <input type="radio" name="14" value="off" checked="checked"><strong>Off</strong>
226 (<code>default = <strong>off</strong></code>)<br/>
227 Associated chargino-neutralino production by quark-antiquark
228 annihilation. With four neutralino species, two chargino ones, and
229 maintaining charge conjugate proceeses separate, this gives 16
230 separate processes, codes 1221 - 1236. The cross section expressions
231 follow [<a href="Bibliography.php" target="page">Boz07</a>].
232 Validation of the FLV and CPV cases has not yet been completed.
235 <br/><br/><strong>SUSY:qqbar2chi+chi-</strong> <input type="radio" name="15" value="on"><strong>On</strong>
236 <input type="radio" name="15" value="off" checked="checked"><strong>Off</strong>
237 (<code>default = <strong>off</strong></code>)<br/>
238 Pair production of charginos by quark-antiquark annihilation. With
239 two chargino species and maintaining mutually charge conjugate
240 processes separate, this gives four separate processes, codes
241 1241 - 1244. The cross section expressions follow [<a href="Bibliography.php" target="page">Boz07</a>].
242 Validation of the FLV and CPV cases has not yet been completed.
245 <h3>Associated Neutralino/Chargino + Squark/Gluino Production</h3>
247 <br/><br/><strong>SUSY:qg2chi0squark</strong> <input type="radio" name="16" value="on"><strong>On</strong>
248 <input type="radio" name="16" value="off" checked="checked"><strong>Off</strong>
249 (<code>default = <strong>off</strong></code>)<br/>
250 Pair production of neutralinos from quark-gluon initial states.
251 The cross section expressions follow [<a href="Bibliography.php" target="page">Boz07</a>].
252 Validation of the FLV and CPV cases has not yet been completed.
255 <br/><br/><strong>SUSY:qg2chi+-squark</strong> <input type="radio" name="17" value="on"><strong>On</strong>
256 <input type="radio" name="17" value="off" checked="checked"><strong>Off</strong>
257 (<code>default = <strong>off</strong></code>)<br/>
258 Associated chargino-squark production from quark-gluon initial states.
259 annihilation. The cross section expressions
260 follow [<a href="Bibliography.php" target="page">Boz07</a>].
261 Validation of the FLV and CPV cases has not yet been completed.
264 <br/><br/><strong>SUSY:qqbar2chi0gluino</strong> <input type="radio" name="18" value="on"><strong>On</strong>
265 <input type="radio" name="18" value="off" checked="checked"><strong>Off</strong>
266 (<code>default = <strong>off</strong></code>)<br/>
267 Associated neutralino-gluino production by quark-antiquark
268 annihilation. Status: not implemented yet.
271 <br/><br/><strong>SUSY:qqbar2chi+-gluino</strong> <input type="radio" name="19" value="on"><strong>On</strong>
272 <input type="radio" name="19" value="off" checked="checked"><strong>Off</strong>
273 (<code>default = <strong>off</strong></code>)<br/>
274 Associated chargino-gluino production by quark-antiquark
275 annihilation. Status: not implemented yet.
278 <h3>Slepton Production</h3>
280 No 2->2 slepton pair production or associated slepton production
281 cross sections have been implemented yet.
283 <h3>R-parity violating squark production</h3>
285 <br/><br/><strong>SUSY:qq2antisquark</strong> <input type="radio" name="20" value="on"><strong>On</strong>
286 <input type="radio" name="20" value="off" checked="checked"><strong>Off</strong>
287 (<code>default = <strong>off</strong></code>)<br/>
288 Redonant squark production via R-parity violating UDD couplings. The
289 couplings must be input using the SLHA2 structure.
292 <input type="hidden" name="saved" value="1"/>
295 echo "<input type='hidden' name='filepath' value='".$_GET["filepath"]."'/>"?>
297 <table width="100%"><tr><td align="right"><input type="submit" value="Save Settings" /></td></tr></table>
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414 <!-- Copyright (C) 2010 Peter Skands, Torbjorn Sjostrand -->