*
* $Id$
*
* $Log$
* Revision 1.2 1996/12/04 17:39:53 cernlib
* Version 7.22 from author
*
*
* This directory was created from /afs/cern.ch/user/m/mclareni/isajet/isajet.car patch isassdoc
ISASUSY 7.21
Decay Modes in the Minimal Supersymmetric Model
Howard Baer
Florida State University
Talahassee, FL 32306
Frank E. Paige
Brookhaven National Laboratory
Upton, NY 11973
S.D. Protopopescu
Brookhaven National Laboratory
Upton, NY 11973
Xerxes Tata
University of Hawaii
Honolulu, HI 96822
The code in patch ISASUSY of ISAJET calculates decay modes of
supersymmetric particles based on the work of H. Baer, M. Bisset, D.
Dzialo (Karatas), X. Tata, J. Woodside, and their collaborators. The
calculations assume the minimal supersymmetric extension of the
standard model. Supersymmetric grand unification is assumed by
default in the chargino and neutralino mass matrices, although the
user can override this by specifying arbitrary U(1) and SU(2) gaugino
masses at the weak scale. The squark, left and right slepton and
sneutrino masses are treated as arbitrary. Soft breaking masses are
input for the 3rd generation; mass eigenstates are computed from
these. Most calculations are done at the tree level, but one-loop
results for gluino loop decays, H -> GM GM and H -> GL GL, loop
corrections to the Higgs mass spectrum and couplings, and QCD
corrections to H -> q qbar are included. The Higgs masses have been
calculated using the effective potential approximation including both
top and bottom Yukawa and mixing effects. Mike Bisset and Xerxes Tata
have contributed the Higgs mass, couplings, and decay routines. Note
that e+e- annihilation to SUSY particles and SUSY Higgs bosons have
been included in ISAJET versions >7.11. The following are NOT included
in this version:
* WH and ZH Higgs production mechanisms in hadronic collisions
* Large tan(beta) solution (tan(beta)<=10 should be chosen)
* Non-degenerate 1st and 2nd generation sfermions
These and other processes may be added in future versions as the physics
interest warrants. Note that the details of the masses and the decay
modes can be quite sensitive to choices of standard model parameters
such as the QCD coupling ALFA3 and the quark masses. To change these,
you must modify subroutine SSMSSM. By default, ALFA3=.12.
All the mass spectrum and branching ratio calculations in ISASUSY
are performed by the call to
SUBROUTINE SSMSSM(XM1,XM2,XMG,XMS,XMTL,XMTR,XMLL,XMLR,XMNL
$,XTANB,XMHA,XMU,XMT,XAT,XMBR,XAB,IALLOW)
where the following are taken to be independent parameters:
XM1 = U(1) gaugino mass
= computed from XMG if > 1E19
XM2 = SU(2) gaugino mass
= computed from XMG if > 1E19
XMG = gluino mass
XMS = common u,d,s,c squark mass
XMTL = left soft breaking stop mass
XMTR = right soft breaking stop mass
XMBR = right soft breaking sbottom mass
XMLL = left slepton mass
XMLR = right slepton mass
XMNL = sneutrino mass
XTANB = tan(beta) = ratio of vev's
= 1/R (of old Baer-Tata notation).
XMU = mu = SUSY Higgs mass
= -2*m_1 of Baer et al.
XMHA = pseudo-scalar Higgs mass
XMT = top quark mass
XAT = stop squark trilinear term
XAB = sbottom squark trilinear term
The variable IALLOW is returned:
IALLOW = 1 if Z1SS is not LSP, 0 otherwise
All variables are of type REAL except IALLOW, which is INTEGER, and all
masses are in GeV. The notation is taken to correspond to that of Haber
and Kane, although the Tata Lagrangian is used internally. All other
standard model parameters are hard wired in this subroutine; they are
not obtained from the rest of ISAJET. The theoretically favored range of
these parameters is
50 < M(gluino) < 2000 GeV
50 < M(squark) < 2000 GeV
50 < M(slepton) < 2000 GeV
-1000 < mu < 1000 GeV
1 < tan(beta) < mt/mb
100 < M(top) < 200 GeV
50 < M(HA) < 1000 GeV
M(t_l), M(t_r) < M(squark)
M(b_r) ~ M(squark)
-1000 < A_t < 1000 GeV
-1000 < A_b < 1000 GeV
It is assumed that the lightest supersymmetric particle is the lightest
neutralino Z1. Some choices of the above parameters may violate this
assumption, yielding a light chargino or light stop squark lighter than
Z1SS. In such cases SSMSSM does not compute any branching ratios and
returns IALLOW = 1.
SSMSSM does not check the parameters or resulting masses against
existing experimental data. SSTEST provides a minimal test. This routine
is called after SSMSSM by ISAJET and ISASUSY and prints suitable warning
messages.
SSMSSM first calculates the other SUSY masses and mixings and puts
them in the common block /SSPAR/:
#include "sspar.inc"
It then calculates the widths and branching ratios and puts them in the
common block /SSMODE/:
#include "ssmode.inc"
Decay modes for a given particle are not necessarily adjacent in this
common block. Note that the branching ratio calculations use the full
matrix elements, which in general will give nonuniform distributions in
phase space, but this information is not saved in /SSMODE/. In
particular, the decays H -> Z + Z* -> Z + f + fbar give no indication
that the f + fbar mass is strongly peaked near the upper limit.
All IDENT codes are defined by parameter statements in the PATCHY
keep sequence SSTYPE:
#include "sstype.inc"
These are based on standard ISAJET but can be changed to interface with
other generators. Since masses except the t mass are hard wired, one
should check the kinematics for any decay before using it with possibly
different masses.
Instead of specifying all the SUSY parameters at the electroweak
scale using the MSSMi commands, one can instead use the SUGRA parameter
to specify in the minimal supergravity framework the common scalar mass
M_0, the common gaugino mass M_(1/2), and the soft trilinear SUSY
breaking parameter A_0 at the GUT scale, the ratio tan(beta) of Higgs
vacuum expectation values at the electroweak scale, and sign(mu), the
sign of the Higgsino mass term. The renormalization group equations are
solved iteratively using Runge-Kutta numerical integration, as follows:
(1) The RGE's are run from the weak scale M_Z up to the GUT scale,
where alpha_1 = alpha_2, taking all thresholds into account. We use
two loop RGE equations for the gauge couplings only.
(2) The GUT scale boundary conditions are imposed, and the RGE's
are run back to M_Z, again taking thresholds into account.
(3) The masses of the SUSY particles and the values of the soft
breaking parameters B and mu needed for radiative symmetry are
computed, e.g.
mu**2(M_Z) = (M_H1**2 - M_H2**2 * tan**2(beta))
/(tan**2(beta)-1) - M_Z**2/2
(4) The 1-loop radiative corrections are computed.
(5) The process is then interated until stable results are
obtained.
This is essentially identical to the procedure used by several other
groups. Other possible constraints such as b-tau unification and limits
on proton decay have not been included.
Patch ISASSRUN of ISAJET provides a main program SSRUN and some
utility programs to produce human readable output. These utilities must
be rewritten if the IDENT codes in /SSTYPE/ are modified. To create the
stand-alone version of ISASUSY with SSRUN, run YPATCHY on isajet.pam
with the following cradle:
\+USE,*ISASUSY. Select all code
\+USE,NOCERN. No CERN Library
\+USE,IMPNONE. Use IMPLICIT NONE
\+EXE. Write everything to ASM
\+PAM. Read PAM file
\+QUIT. Quit
Compile, link, and run the resulting program, and follow the prompts for
input. Patch ISASSRUN also contains a main program SUGRUN that reads
the SUGRA parameters, solves the renormalization group equations, and
calculates the masses and branching ratios. To create the stand-alone
version of ISASUGRA, run YPATCHY with the following cradle:
\+USE,*ISASUGRA. Select all code
\+USE,NOCERN. No CERN Library
\+USE,IMPNONE. Use IMPLICIT NONE
\+EXE. Write everything to ASM
\+PAM. Read PAM file
\+QUIT. Quit
To produce the documentation, run YPATCHY with the following cradle:
\+USE,CDESUSY,ISASSDOC
\+EXE
\+PAM
\+QUIT
This documentation is automatically appended to that for ISAJET.
ISASUSY is written in ANSI standard Fortran 77 except that
IMPLICIT NONE is used if +USE,IMPNONE is selected in the Patchy cradle.
All variables are explicitly typed, and variables starting with
I,J,K,L,M,N are not necessarily integers. All external names such as
the names of subroutines and common blocks start with the letters SS.
Most calculations are done in double precision. If +USE,NOCERN is
selected in the Patchy cradle, then the Cernlib routines EISRS1 and its
auxiliaries to calculate the eigenvalues of a real symmetric matrix and
DDILOG to calculate the dilogarithm function are included. Hence it is
not necessary to link with Cernlib.
The physics assumptions and details of incorporating the Minimal
Supersymmetric Model into ISAJET have appeared in a conference
proceedings entitled
H. Baer, F. Paige, S. Protopopescu and X. Tata,
"Simulating Supersymmetry with ISAJET 7.0/ISASUSY 1.0",
which has appeared in the proceedings of the workshop on "Physics at
Current Accelerators and Supercolliders", ed. J. Hewett, A. White and
D. Zeppenfeld, (Argonne National Laboratory, 1993). Detailed
references may be found therein. Users wishing to cite an appropriate
source may cite the above report.