5 * Revision 1.2 1996/12/04 17:39:53 cernlib
6 * Version 7.22 from author
9 * This directory was created from /afs/cern.ch/user/m/mclareni/isajet/isajet.car patch isassdoc
11 Decay Modes in the Minimal Supersymmetric Model
14 Florida State University
18 Brookhaven National Laboratory
22 Brookhaven National Laboratory
31 The code in patch ISASUSY of ISAJET calculates decay modes of
32 supersymmetric particles based on the work of H. Baer, M. Bisset, D.
33 Dzialo (Karatas), X. Tata, J. Woodside, and their collaborators. The
34 calculations assume the minimal supersymmetric extension of the
35 standard model. Supersymmetric grand unification is assumed by
36 default in the chargino and neutralino mass matrices, although the
37 user can override this by specifying arbitrary U(1) and SU(2) gaugino
38 masses at the weak scale. The squark, left and right slepton and
39 sneutrino masses are treated as arbitrary. Soft breaking masses are
40 input for the 3rd generation; mass eigenstates are computed from
41 these. Most calculations are done at the tree level, but one-loop
42 results for gluino loop decays, H -> GM GM and H -> GL GL, loop
43 corrections to the Higgs mass spectrum and couplings, and QCD
44 corrections to H -> q qbar are included. The Higgs masses have been
45 calculated using the effective potential approximation including both
46 top and bottom Yukawa and mixing effects. Mike Bisset and Xerxes Tata
47 have contributed the Higgs mass, couplings, and decay routines. Note
48 that e+e- annihilation to SUSY particles and SUSY Higgs bosons have
49 been included in ISAJET versions >7.11. The following are NOT included
52 * WH and ZH Higgs production mechanisms in hadronic collisions
54 * Large tan(beta) solution (tan(beta)<=10 should be chosen)
56 * Non-degenerate 1st and 2nd generation sfermions
58 These and other processes may be added in future versions as the physics
59 interest warrants. Note that the details of the masses and the decay
60 modes can be quite sensitive to choices of standard model parameters
61 such as the QCD coupling ALFA3 and the quark masses. To change these,
62 you must modify subroutine SSMSSM. By default, ALFA3=.12.
64 All the mass spectrum and branching ratio calculations in ISASUSY
65 are performed by the call to
67 SUBROUTINE SSMSSM(XM1,XM2,XMG,XMS,XMTL,XMTR,XMLL,XMLR,XMNL
68 $,XTANB,XMHA,XMU,XMT,XAT,XMBR,XAB,IALLOW)
70 where the following are taken to be independent parameters:
72 XM1 = U(1) gaugino mass
73 = computed from XMG if > 1E19
74 XM2 = SU(2) gaugino mass
75 = computed from XMG if > 1E19
77 XMS = common u,d,s,c squark mass
78 XMTL = left soft breaking stop mass
79 XMTR = right soft breaking stop mass
80 XMBR = right soft breaking sbottom mass
81 XMLL = left slepton mass
82 XMLR = right slepton mass
84 XTANB = tan(beta) = ratio of vev's
85 = 1/R (of old Baer-Tata notation).
86 XMU = mu = SUSY Higgs mass
87 = -2*m_1 of Baer et al.
88 XMHA = pseudo-scalar Higgs mass
90 XAT = stop squark trilinear term
91 XAB = sbottom squark trilinear term
93 The variable IALLOW is returned:
95 IALLOW = 1 if Z1SS is not LSP, 0 otherwise
97 All variables are of type REAL except IALLOW, which is INTEGER, and all
98 masses are in GeV. The notation is taken to correspond to that of Haber
99 and Kane, although the Tata Lagrangian is used internally. All other
100 standard model parameters are hard wired in this subroutine; they are
101 not obtained from the rest of ISAJET. The theoretically favored range of
104 50 < M(gluino) < 2000 GeV
105 50 < M(squark) < 2000 GeV
106 50 < M(slepton) < 2000 GeV
107 -1000 < mu < 1000 GeV
108 1 < tan(beta) < mt/mb
109 100 < M(top) < 200 GeV
110 50 < M(HA) < 1000 GeV
111 M(t_l), M(t_r) < M(squark)
113 -1000 < A_t < 1000 GeV
114 -1000 < A_b < 1000 GeV
116 It is assumed that the lightest supersymmetric particle is the lightest
117 neutralino Z1. Some choices of the above parameters may violate this
118 assumption, yielding a light chargino or light stop squark lighter than
119 Z1SS. In such cases SSMSSM does not compute any branching ratios and
122 SSMSSM does not check the parameters or resulting masses against
123 existing experimental data. SSTEST provides a minimal test. This routine
124 is called after SSMSSM by ISAJET and ISASUSY and prints suitable warning
127 SSMSSM first calculates the other SUSY masses and mixings and puts
128 them in the common block /SSPAR/:
132 It then calculates the widths and branching ratios and puts them in the
133 common block /SSMODE/:
135 #include "ssmode.inc"
137 Decay modes for a given particle are not necessarily adjacent in this
138 common block. Note that the branching ratio calculations use the full
139 matrix elements, which in general will give nonuniform distributions in
140 phase space, but this information is not saved in /SSMODE/. In
141 particular, the decays H -> Z + Z* -> Z + f + fbar give no indication
142 that the f + fbar mass is strongly peaked near the upper limit.
144 All IDENT codes are defined by parameter statements in the PATCHY
145 keep sequence SSTYPE:
147 #include "sstype.inc"
149 These are based on standard ISAJET but can be changed to interface with
150 other generators. Since masses except the t mass are hard wired, one
151 should check the kinematics for any decay before using it with possibly
154 Instead of specifying all the SUSY parameters at the electroweak
155 scale using the MSSMi commands, one can instead use the SUGRA parameter
156 to specify in the minimal supergravity framework the common scalar mass
157 M_0, the common gaugino mass M_(1/2), and the soft trilinear SUSY
158 breaking parameter A_0 at the GUT scale, the ratio tan(beta) of Higgs
159 vacuum expectation values at the electroweak scale, and sign(mu), the
160 sign of the Higgsino mass term. The renormalization group equations are
161 solved iteratively using Runge-Kutta numerical integration, as follows:
163 (1) The RGE's are run from the weak scale M_Z up to the GUT scale,
164 where alpha_1 = alpha_2, taking all thresholds into account. We use
165 two loop RGE equations for the gauge couplings only.
167 (2) The GUT scale boundary conditions are imposed, and the RGE's
168 are run back to M_Z, again taking thresholds into account.
170 (3) The masses of the SUSY particles and the values of the soft
171 breaking parameters B and mu needed for radiative symmetry are
173 mu**2(M_Z) = (M_H1**2 - M_H2**2 * tan**2(beta))
174 /(tan**2(beta)-1) - M_Z**2/2
176 (4) The 1-loop radiative corrections are computed.
178 (5) The process is then interated until stable results are
181 This is essentially identical to the procedure used by several other
182 groups. Other possible constraints such as b-tau unification and limits
183 on proton decay have not been included.
185 Patch ISASSRUN of ISAJET provides a main program SSRUN and some
186 utility programs to produce human readable output. These utilities must
187 be rewritten if the IDENT codes in /SSTYPE/ are modified. To create the
188 stand-alone version of ISASUSY with SSRUN, run YPATCHY on isajet.pam
189 with the following cradle:
191 \+USE,*ISASUSY. Select all code
192 \+USE,NOCERN. No CERN Library
193 \+USE,IMPNONE. Use IMPLICIT NONE
194 \+EXE. Write everything to ASM
198 Compile, link, and run the resulting program, and follow the prompts for
199 input. Patch ISASSRUN also contains a main program SUGRUN that reads
200 the SUGRA parameters, solves the renormalization group equations, and
201 calculates the masses and branching ratios. To create the stand-alone
202 version of ISASUGRA, run YPATCHY with the following cradle:
204 \+USE,*ISASUGRA. Select all code
205 \+USE,NOCERN. No CERN Library
206 \+USE,IMPNONE. Use IMPLICIT NONE
207 \+EXE. Write everything to ASM
211 To produce the documentation, run YPATCHY with the following cradle:
213 \+USE,CDESUSY,ISASSDOC
218 This documentation is automatically appended to that for ISAJET.
220 ISASUSY is written in ANSI standard Fortran 77 except that
221 IMPLICIT NONE is used if +USE,IMPNONE is selected in the Patchy cradle.
222 All variables are explicitly typed, and variables starting with
223 I,J,K,L,M,N are not necessarily integers. All external names such as
224 the names of subroutines and common blocks start with the letters SS.
225 Most calculations are done in double precision. If +USE,NOCERN is
226 selected in the Patchy cradle, then the Cernlib routines EISRS1 and its
227 auxiliaries to calculate the eigenvalues of a real symmetric matrix and
228 DDILOG to calculate the dilogarithm function are included. Hence it is
229 not necessary to link with Cernlib.
231 The physics assumptions and details of incorporating the Minimal
232 Supersymmetric Model into ISAJET have appeared in a conference
235 H. Baer, F. Paige, S. Protopopescu and X. Tata,
236 "Simulating Supersymmetry with ISAJET 7.0/ISASUSY 1.0",
238 which has appeared in the proceedings of the workshop on "Physics at
239 Current Accelerators and Supercolliders", ed. J. Hewett, A. White and
240 D. Zeppenfeld, (Argonne National Laboratory, 1993). Detailed
241 references may be found therein. Users wishing to cite an appropriate
242 source may cite the above report.