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2 | \section{Changes in Recent Versions} | |

3 | ||

4 | This section contains a record of changes in recently released | |

5 | versions of ISAJET, taken from the memoranda distributed to users. | |

6 | Note that the released version numbers are not necessarily consecutive. | |

7 | ||

8 | \subsection{Version~7.51, May 2000} | |

9 | ||

10 | Several improvements in the SUSY RGE's have been made. All | |

11 | two-loop terms including both gauge and Yukawa couplings and the | |

12 | contributions from right-handed neutrinos are now included. There is a | |

13 | new keyword \verb|SSBCSC| to specify a scale other than the GUT scale | |

14 | for the RGE boundary conditions. | |

15 | ||

16 | The process $Z+\gamma$ is now included in \verb|WPAIR|. (This | |

17 | was omitted because it has no contribution from triple gauge boson | |

18 | couplings.) | |

19 | ||

20 | An incorrect type declaration produced unphysical results for | |

21 | beamsstrahlung on some computers. This has been fixed. While the bug is | |

22 | serious for $e^+e^-$ with the \verb|EEBEAM| option, it has no effect on | |

23 | other processes. Some other minor bugs have also been fixed. | |

24 | ||

25 | \subsection{Version~7.47, December 1999} | |

26 | ||

27 | There are several improvements in the treatment of | |

28 | supersymmetry. The Anomaly Mediated SUSY Breaking model of of Randall | |

29 | and Sundrum and of Gherghetta, Giudice, and Wells (hep-ph/9904378) has | |

30 | been added. The parameters of the model are a universal scalar mass | |

31 | $m_0$ at the GUT scale, a gravitino mass $m_{3/2}$, and the usual | |

32 | $\tan\beta$ and $\sgn\mu$. These are set by the \verb|AMSB| keyword. The | |

33 | renormalization group equations have been extended to include two-loop | |

34 | Yukawa terms and right-handed sneutrinos (with default masses above the | |

35 | Planck scale). The $\tilde\nu_R$ play a role in the evolution for the | |

36 | inverted hierarchy models of Bagger, Feng, and Polonsky, hep-ph/9905292. | |

37 | SUSY loop corrections to Yukawa couplings have been incorporated in the | |

38 | SUSY mass calculations. | |

39 | ||

40 | The Helas library of Murayama, Watanabe, and Hagiwara has been | |

41 | incorporated together with a simple multi-body phase space generator. | |

42 | This makes it possible to use code generated by MadGraph to produce | |

43 | multi-body hard scattering processes. As a first example, a \verb|ZJJ| | |

44 | process that generates $Z + \hbox{2 jets}$ has been added, with the $Z$ | |

45 | treated as a narrow resonance. Additional processes may be added in | |

46 | future releases. | |

47 | ||

48 | A new \verb|EXTRADIM| process has been added to generate | |

49 | Kaluza-Klein graviton production in association with a jet or photon in | |

50 | models with extra dimensions at the TeV scale. The cross sections are | |

51 | from G.F.Giudice et al., hep-ph/9811291. We thank I. Hinchliffe and L. | |

52 | Vacavant for providing this. | |

53 | ||

54 | A number of bugs have been fixed, including in particular one in | |

55 | the decay $\widetilde W_i \to \widetilde Z_j \tau \nu$. | |

56 | ||

57 | \subsection{Version~7.44, April 1999} | |

58 | ||

59 | A serious bug introduced in Version~7.42 that could lead to | |

60 | matrix elements being stored for the wrong mode has been corrected. | |

61 | Some sign errors in the matrix elements for gaugino decays have also | |

62 | been corrected. | |

63 | ||

64 | \subsection{Version~7.42, January 1999} | |

65 | ||

66 | Beginning with this version, matrix elements are taken into | |

67 | account in the event generator as well as in the calculation of decay | |

68 | widths for MSSM three-body decays of the form $\tilde A \to \tilde B f | |

69 | \bar f$, where $\tilde A$ and $\tilde B$ are gluinos, charginos, or | |

70 | neutralinos. This is implemented by having ISASUSY save the poles and | |

71 | their couplings when calculating the decay width and then using these | |

72 | to reconstruct the matrix element. Other three-body decays may be | |

73 | included in the future. Decays selected with \verb|FORCE| use the | |

74 | appropriate matrix elements. | |

75 | ||

76 | As part of the changes to implement these matrix elements, the | |

77 | format of the decay table has changed. It now starts with a header | |

78 | line; if this does not match the internal version, then a warning is | |

79 | printed. The decay table now includes an index MELEM that specifies the | |

80 | matrix element to be used for all processes. This is also used for | |

81 | \verb|FORCE| decays and is printed on the run listing for them. SUSY | |

82 | 3-body decays have internally generated negative values of MELEM. | |

83 | ||

84 | This version also includes both initial state radiation and | |

85 | beamstrahlung for $e^+e^-$ interactions. For initial state radiation | |

86 | (bremsstrahlung), if the \verb|EEBREM| keyword is selected, an electron | |

87 | structure function will be used. For a convolution of both | |

88 | bremsstrahlung and beamstrahlung, the keyword \verb|EEBEAM| must be | |

89 | used, with appropriate inputs (see documentation). | |

90 | ||

91 | \subsection{Version~7.40, October 1998} | |

92 | ||

93 | A new process WHIGGS generates $W^\pm+H$ and $Z+H$ events for | |

94 | both the Standard Model and SUSY models and also Higgs pair production | |

95 | for SUSY models. The types and $W$ decay modes are selected with | |

96 | JETTYPE and WMODE as for WPAIR events. This process is of particular | |

97 | interest for producing fairly light Higgs bosons at the Tevatron. See | |

98 | the documentation for more details. | |

99 | ||

100 | Some non-minimal GMSB models can be generated using a new | |

101 | keyword GMSB2. The optional parameters are an extra factor between the | |

102 | gaugino and scalar masses, shifts in the Higgs masses, a $D$-term | |

103 | proportional to hypercharge, and independent numbers of messenger | |

104 | fields for the three gauge groups. The documentation gives more | |

105 | details and references. | |

106 | ||

107 | The default for SUGRA models has been changed to use | |

108 | $\alpha_s(M_Z)=0.118$, the experimental value. This means that the | |

109 | couplings do not exactly unify at the GUT scale, presumably because of | |

110 | the effects of heavy particles. The keyword AL3UNI can be used to | |

111 | select exact unification, which produces too large a value for | |

112 | $\alpha_s(M_Z)$. | |

113 | ||

114 | A number of three-body slepton decays that occur through | |

115 | left-right mixing are now included. These are obviously small but | |

116 | might compete with gravitino decays. In particular, a decay like | |

117 | $\tilde\mu_R \to \tilde\tau_1 \nu\bar\nu$ might lead to a wrong | |

118 | momentum measurement in the muon system. So far we have found no case | |

119 | in which this is probable. | |

120 | ||

121 | The new release also includes a separate Unix tar file | |

122 | \verb|mcpp.tar| containing C++ code to read a standard ISAJET output | |

123 | file and copy all the information into C++ classes. The tar file | |

124 | contains makefiles for Software Release Tools, documentation, and | |

125 | examples as well as the code. | |

126 | ||

127 | \subsection{Version~7.37, April 1998} | |

128 | ||

129 | Version~7.37 incorporates Gauge Mediated SUSY Breaking models | |

130 | for the first time. In these models, SUSY is broken in a hidden sector | |

131 | at a relatively low scale, and the masses of the MSSM fields are then | |

132 | produced through ordinary gauge interactions with messenger fields. | |

133 | The parameters of the GMSB model in ISAJET are $M_m$, the messenger | |

134 | mass scale; $\Lambda_m = F_m/M_m$, where $F_m$ is the SUSY breaking | |

135 | scale in the messenger sector; $N_5$, the number of messenger fields; | |

136 | the usual $\tan\beta$ and $\sgn\mu$; and $C_{\rm grav} \ge 1$, a | |

137 | factor which scales the gravitino mass and hence the lifetime for the | |

138 | lightest MSSM particle to decay into it. | |

139 | ||

140 | GMSB models have a light gravitino $\tilde G$ as the lightest | |

141 | SUSY particle. The phenomenology of the model depends mainly on the | |

142 | nature of the next lightest SUSY particle, a $\tilde\chi_1^0$ or a | |

143 | $\tilde\tau_1$, which changes with the number $N_5$ of messengers. The | |

144 | phenomenology also depends on the lifetime for the $\tilde\chi_1^0 \to | |

145 | \tilde G \gamma$ or $\tilde\tau_1 \to \tilde G \tau$ decay; this | |

146 | lifetime can be short or very long. All the relevant decays are | |

147 | included except for $\tilde\mu \to \nu \nu \tilde\tau_1$, which is very | |

148 | suppressed. | |

149 | ||

150 | The keyword MGVTNO allows the user to independently input a | |

151 | gravitino gravitino mass for the MSSM option. This allows studies of | |

152 | SUGRA (or other types) of models where the gravitino is the LSP. | |

153 | ||

154 | Version~7.37 also contains an extension of the SUGRA model | |

155 | with a variety of non-universal gaugino and sfermion masses and $A$ | |

156 | terms at the GUT scale. This makes it possible to study, for example, | |

157 | how well the SUGRA assumptions can be tested. | |

158 | ||

159 | Two significant bugs have also been corrected. The decay modes | |

160 | for $B^*$ mesons were missing from the decay table since Version~7.29 | |

161 | and have been restored. A sign error in the interference term for | |

162 | chargino production has been corrected, leading to a larger chargino | |

163 | pair cross section at the Tevatron. | |

164 | ||

165 | \subsection{Version 7.32, November 1997} | |

166 | ||

167 | This version makes several corrections in various chargino and | |

168 | neutralino widths, thus changing the branching ratios for large | |

169 | $\tan\beta$. For $\tilde\chi_2^0$, for example, the $\tilde\chi_1^0 | |

170 | b\bar b$ branching ratio is decreased significantly, while the | |

171 | $\tilde\chi_1^0 \tau^+ \tau^-$ one is increased. Thus the SUGRA | |

172 | phenomenology for $\tan\beta \sim 30$ is modified substantially. | |

173 | ||

174 | The new version also fixes a few bugs, including a possible | |

175 | numerical precision problem in the Drell-Yan process at high mass and | |

176 | $q_T$. It also includes a missing routine for the Zebra interface. | |

177 | ||

178 | \subsection{Version 7.31, August 1997} | |

179 | ||

180 | Version fixes a couple of bugs in Version~7.29. In | |

181 | particular, the JETTYPE selection did not work correctly for | |

182 | supersymmetric Higgs bosons, and there was an error in the interactive | |

183 | interface for MSSM input. Since these could lead to incorrect results, | |

184 | users should replace the old version. We thank Art Kreymer for finding | |

185 | these problems. | |

186 | ||

187 | Since top quarks decay before they have time to hadronize, | |

188 | they are now put directly onto the particle list. Top hadrons ($t\bar | |

189 | u$, $t\bar d$, etc.) no longer appear, and FORCE should be used | |

190 | directly for the top quark, i.e. | |

191 | \begin{verbatim} | |

192 | FORCE | |

193 | 6,11,-12,5/ | |

194 | \end{verbatim} | |

195 | ||

196 | The documentation has been converted to LaTeX. Run either | |

197 | LaTeX~2.09 or LaTeX~2e three times to resolve all the forward | |

198 | references. Either US (8.5x11 inch) or A4 size paper can be used. | |

199 | ||

200 | \subsection{Version 7.30, July 1997} | |

201 | ||

202 | This version fixes a couple of bugs in the previous version. | |

203 | In particular, the JETTYPE selection did not work correctly for | |

204 | supersymmetric Higgs bosons, and there was an error in the interactive | |

205 | interface for MSSM input. Since these could lead to incorrect results, | |

206 | users should replace the old version. We thank Art Kreymer for finding | |

207 | these problems. | |

208 | ||

209 | Since top quarks decay before they have time to hadronize, | |

210 | they are now put directly onto the particle list. Top hadrons ($t\bar | |

211 | u$, $tud$, etc.) no longer appear, and FORCE should be used directly | |

212 | for the top quark, i.e. | |

213 | \begin{verbatim} | |

214 | FORCE | |

215 | 6,11,-12,5/ | |

216 | \end{verbatim} | |

217 | ||

218 | The documentation has been converted to \LaTeX. Run either | |

219 | \LaTeX~2.09 or \LaTeX~2e three times to resolve all the forward | |

220 | references. Either US ($8.5\times11$~inch) or A4 size paper can be | |

221 | used. | |

222 | ||

223 | \subsection{Version 7.29, May 1997} | |

224 | ||

225 | While the previous version was applicable for large as well as | |

226 | small $\tan\beta$, it did contain approximations for the 3-body decays | |

227 | $\tilde g \to t \bar b \tilde W_i$, $\tilde Z_i \to b \bar b \tilde | |

228 | Z_j, \tau \tau \tilde Z_j$, and $\tilde W_i \to \tau \nu \tilde Z_j$. | |

229 | The complete tree-level calculations for three body decays of the | |

230 | gluino, chargino and neutralino, with all Yukawa couplings and | |

231 | mixings, have now been included (thanks mainly to M. Drees). We have | |

232 | compared our branching ratios with those calculated by A.~Bartl and | |

233 | collaborators; the agreement is generally good. | |

234 | ||

235 | The decay patterns of gluinos, charginos and neutralinos may | |

236 | differ from previous expectations if $\tan\beta$ is large. In | |

237 | particular, decays into $\tau$'s and $b$'s are often enhanced, while | |

238 | decays into $e$'s and $\mu$'s are reduced. It could be important for | |

239 | experiments to study new types of signatures, since the cross sections | |

240 | for conventional signatures may be considerably reduced. | |

241 | ||

242 | We have also corrected several bugs, including a fairly | |

243 | serious one in the selection of jet types for SUSY Higgs. We thank | |

244 | A.~Kreymer for pointing this out to us. | |

245 | ||

246 | \subsection{Version 7.27, January 1997} | |

247 | ||

248 | The new version contains substantial improvements in the | |

249 | treatment of the Minimal Supersymmetric Standard Model (MSSM) and the | |

250 | SUGRA model. The squarks of the first two generations are no longer | |

251 | assumed to be degenerate. The mass splittings and all the two-body | |

252 | decay modes are now correctly calculated for large $\tan\beta$. While | |

253 | there are still some approximations for three-body modes, ISAJET is | |

254 | now usable for the whole range $1 \simle \tan\beta \simle M_t/M_b$. The | |

255 | most interesting new feature for large $\tan\beta$ is that third | |

256 | generation modes can be strongly enhanced or even completely dominant. | |

257 | ||

258 | To accomodate these changes it was necessary to change the | |

259 | MSSM input parameters. To avoid confusion, the MSSM keywords have | |

260 | been renamed MSSM[A-C] instead of MSSM[1-3], and the order of the | |

261 | parameters has been changed. See the input section of the manual for | |

262 | details. | |

263 | ||

264 | Treatment of the MSSM Higgs sector has also been improved. In | |

265 | the renormalization group equations the Higgs couplings are frozen at | |

266 | a higher scale, $Q = \sqrt{M(\tilde t_L)M(\tilde t_R)}$. Running | |

267 | $t$, $b$ and $\tau$ masses evaluated at that scale are used to | |

268 | reproduce the dominant 2-loop effects. There is some sensitivity to | |

269 | the choice of $Q$; our choice seems to give fairly stable results over | |

270 | a wide range of parameters and reasonable agreement with other | |

271 | calculations. In particular, the resulting light Higgs masses are | |

272 | significantly lower than those from Version~7.22. | |

273 | ||

274 | The default parton distributions have been updated to CTEQ3L. | |

275 | A bug in the PDFLIB interface and other minor bugs have been fixed. | |

276 | ||

277 | \subsection{Version 7.22, July 1996} | |

278 | ||

279 | The new version fixes errors in $\tilde b \to \tilde W t$ and in | |

280 | some $\tilde t$ decays and Higgs decays. It also contains a new decay | |

281 | table with updated $\tau$, $c$, and $b$ decays, based loosely on the | |

282 | QQ decay package from CLEO. The updated decays are less detailed than | |

283 | the full CLEO QQ program but an improvement over what existed before. | |

284 | The new decays involve a number of additional resonances, including | |

285 | $f_0(980)$, $a_1(1260)$, $f_2(1270)$, $K_1(1270)$, $K_1^*(1400)$, | |

286 | $K_2^*(1430)$, $\chi_{c1,2,3}$, and $\psi(2S)$, so users may have to | |

287 | change their interface routines. | |

288 | ||

289 | A number of other small bugs have been corrected. | |

290 | ||

291 | \subsection{Version 7.20, June 1996} | |

292 | ||

293 | The new version corrects both errors introduced in Version~7.19 | |

294 | and longstanding errors in the final state QCD shower algorithm. It | |

295 | also includes the top mass in the cross sections for $g b \to W t$ and | |

296 | $g t \to Z t$. When the $t$ mass is taken into account, the process $g | |

297 | t \to W b$ can have a pole in the physical region, so it has been | |

298 | removed; see the documentation for more discussion. | |

299 | ||

300 | Steve Tether recently pointed out to us that the anomalous | |

301 | dimension for the $q \to q g$ branching used in the final state QCD | |

302 | branching algorithm was incorrect. In investigating this we found an | |

303 | additional error, a missing factor of $1/3$ in the $g \to q \bar q$ | |

304 | branching. The first error produces a small but non-negligible | |

305 | underestimate of gluon radiation from quarks. The second overestimates | |

306 | quark pair production from gluons by about a factor of 3. In | |

307 | particular, this means that backgrounds from heavy quarks $Q$ coming | |

308 | from $g \to Q \bar Q$ have been overestimated. | |

309 | ||

310 | The new version also allows the user to set arbitrary masses | |

311 | for the $U(1)$ and $SU(2)$ gaugino mases in the MSSM rather than | |

312 | deriving these from the gluino mass using grand unification. This | |

313 | could be useful in studying one of the SUSY interpretations of a CDF | |

314 | $ee\gamma\gamma\etmiss$ event recently suggested by Ambrosanio, Kane, | |

315 | Kribs, Martin and Mrenna. Note, however, that radiative decay are | |

316 | {\it not} included, although the user can force them and multiply by | |

317 | the appropriate branching ratios calculated by Haber and Wyler, | |

318 | Nucl.{} Phys.{} B323, 267 (1989). No explicit provision for the decay | |

319 | $\tilde Z_1 \to \tilde G \gamma$ of the lightest zino into a gravitino | |

320 | or goldstino and a photon has been made, but forcing the decay $\tilde | |

321 | Z_1 \to \nu\gamma$ has the same effect for any collider detector. | |

322 | ||

323 | A number of other minor bugs have also been corrected. | |

324 | ||

325 | \subsection{Version 7.16, October 1995} | |

326 | ||

327 | The new version includes $e^+e^-$ cross sections for both SUSY | |

328 | and Standard Model particles with polarized beams. The $e^-$ and $e^+$ | |

329 | polarizations are specified with a new keyword EPOL. Polarization | |

330 | appears to be quite useful in studying SUSY particles at an $e^+e^-$ | |

331 | collider. | |

332 | ||

333 | The new release also includes some bug fixes for $pp$ reactions, | |

334 | so you should upgrade even if you do not plan to use the polarized | |

335 | $e^+e^-$ cross sections. | |

336 | ||

337 | \subsection{Version 7.13, September 1994} | |

338 | ||

339 | Version 7.13 of ISAJET fixes a bug that we introduced in the | |

340 | recently released 7.11 and another bug in $\tilde g \to \tilde q \bar | |

341 | q$. We felt it was essential to fix these bugs despite the | |

342 | proliferation of versions. | |

343 | ||

344 | The new version includes the cross sections for the $e^+e^-$ | |

345 | production of squarks, sleptons, gauginos, and Higgs bosons in Minimal | |

346 | Supersymmetric Standard Model (MSSM) or the minimal supergravity | |

347 | (SUGRA) model, including the effects of cascade decays. To generate | |

348 | such events, select the \verb|E+E-| reaction type and either SUGRA or | |

349 | MSSM, e.g., | |

350 | \begin{verbatim} | |

351 | SAMPLE E+E- JOB | |

352 | 300.,50000,10,100/ | |

353 | E+E- | |

354 | SUGRA | |

355 | 100,100,0,2,-1/ | |

356 | TMASS | |

357 | 170,-1,1/ | |

358 | END | |

359 | STOP | |

360 | \end{verbatim} | |

361 | The effects of spin correlations in the production and decay, e.g., in | |

362 | $e^+e^- \to \widetilde W_1^+ \widetilde W_1^-$, are not included. | |

363 | ||

364 | It should be noted that the Standard Model $e^+e^-$ generator in | |

365 | ISAJET does not include Bhabba scattering or $W^+W^-$ and $Z^0Z^0$ | |

366 | production. Also, its hadronization model is cruder than that | |

367 | available in some other generators. | |

368 | ||

369 | \subsection{Version 7.11, September 1994} | |

370 | ||

371 | The new version includes the cross sections for the $e^+e^-$ | |

372 | production of squarks, sleptons, gauginos, and Higgs bosons in Minimal | |

373 | Supersymmetric Standard Model (MSSM) or the minimal supergravity | |

374 | (SUGRA) model including the effects of cascade decays. To generate | |

375 | such events, select the \verb|E+E-| reaction type and either SUGRA or | |

376 | MSSM, e.g., | |

377 | \begin{verbatim} | |

378 | SAMPLE E+E- JOB | |

379 | 300.,50000,10,100/ | |

380 | E+E- | |

381 | SUGRA | |

382 | 100,100,0,2,-1/ | |

383 | TMASS | |

384 | 170,-1,1/ | |

385 | END | |

386 | STOP | |

387 | \end{verbatim} | |

388 | The effects of spin correlations in the production and decay, e.g., in | |

389 | $e^+e^- \to \widetilde W_1^+ \widetilde W_1^-$, are not included. | |

390 | ||

391 | It should be noted that the Standard Model $e^+e^-$ generator in | |

392 | ISAJET does not include Bhabba scattering or $W^+W^-$ and $Z^0Z^0$ | |

393 | production. Also, its hadronization model is cruder than that | |

394 | available in some other generators. | |

395 | ||

396 | \subsection{Version 7.10, July 1994} | |

397 | ||

398 | This version adds a new option that solves the renormalization group | |

399 | equations to calculate the Minimal Supersymmetric Standard Model (MSSM) | |

400 | parameters in the minimal supergravity (SUGRA) model, assuming only that the | |

401 | low energy theory has the minimal particle content, that electroweak | |

402 | symmetry is radiatively broken, and that R-parity is conserved. The minimal | |

403 | SUGRA model has just four parameters, which are taken to be the common | |

404 | scalar mass $m_0$, the common gaugino mass $m_{1/2}$, the common trilinear | |

405 | SUSY breaking term $A_0$, all defined at the GUT scale, and $\tan\beta$; the | |

406 | sign of $\mu$ must also be given. The renormalization group equations are | |

407 | solved iteratively using Runge-Kutta integration including the correct | |

408 | thresholds. This program can be used either alone or as part of the event | |

409 | generator. In the latter case, the parameters are specified using | |

410 | \begin{verse} | |

411 | SUGRA\\ | |

412 | $m_0$, $m_{1/2}$, $A_0$, $\tan\beta$, $\sgn\mu$ | |

413 | \end{verse} | |

414 | While the SUGRA option is less general than the MSSM, it is theoretically | |

415 | attractive and provides a much more managable parameter space. | |

416 | ||

417 | In addition there have been a number of improvements and bug fixes. An | |

418 | occasional infinite loop in the minimum bias generator has been fixed. A few | |

419 | SUSY cross sections and decay modes and the JETTYPE flags for SUSY | |

420 | particles have been corrected. The treatment of $B$ baryons has been | |

421 | improved somewhat. | |

422 | ||

423 | \end{document} |