SUSY examples

The SUSY routines and commonblock variables are described in section . To illustrate the usage of the switches and parameters, we give three simple examples.

Example 1: Light Stop
The first example is an MSSM model with a light neutralino $\tilde{\chi}_1$ and a light stop $\tilde{\mathrm t}_1$, so that $\t\to \tilde{\mathrm t}_1\tilde{\chi}_1$ can occur. The input parameters are
IMSS(1)=1, RMSS(1)=70., RMSS(2)=70., RMSS(3)=225., RMSS(4)=-40., RMSS(5)=1.5,
RMSS(6)=100., RMSS(7)=125., RMSS(8)=250., RMSS(9)=250., RMSS(10)=1500.,
RMSS(11)=1500., RMSS(12)=-128., RMSS(13)=100., RMSS(14)=125., RMSS(15)=800.,
RMSS(16)=800., RMSS(17)=0., and RMSS(19)=400.0.
The top mass is fixed at 175 GeV, PMAS(6,1)=175.0. The resulting model has $M_{\tilde{\mathrm t}_1}=55$ GeV and $M_{\tilde{\chi}_1}=38$ GeV. IMSS(1)=1 turns on the MSSM simulation. By default, there are no intrinsic relations between the gaugino masses, so $M_1=70$ GeV, $M_2=70$ GeV, and $M_3=225$ GeV. The pole mass of the gluino is slightly higher than the parameter $M_3$, and the decay $\tilde{\mathrm g}\to\tilde{\mathrm t}_1^*\t +\tilde{\mathrm t}_1\overline{\mathrm{t}}$ occurs almost 100% of the time.

Example 2: Approximate SUGRA
The second example is an approximate SUGRA model. The input parameters are
IMSS(1)=2, RMSS(1)=200., RMSS(4)=1., RMSS(5)=10., RMSS(8)=800., and
RMSS(16)=0.0.
The resulting model has $M_{\tilde{\mathrm d}_L}=901$ GeV, $M_{\tilde{\mathrm u}_R}=890$ GeV, $M_{\tilde{\mathrm t}_1}=538$ GeV, $M_{\tilde{\mathrm e}_L}=814$ GeV, $M_{\tilde{\mathrm g}}=560$ GeV, $M_{\tilde{\chi}_1}=80$ GeV, $M_{\tilde{\chi}^{\pm}_1}=151$ GeV, $M_{\mathrm{h}}=110$ GeV, and $M_{A}=883$ GeV. It corresponds to the choice $M_0$=800 GeV, $M_{1/2}=$200 GeV, $\tan\beta=10$, $A_0=0$, and sign($\mu$)$>0$. The output is similar to an ISASUSY run, but there is not exact agreement.

Example 3: Calling ISASUSY 7.58 at runtime
The third example shows how to use the built-in interface to ISASUSY. First, the PYTHIA source code needs to be changed. Rename the function VISAJE to, for example, FDUMMY, rename the subroutine SUGRA to e.g. SDUMMY, and recompile. In the calling program, set IMSS(1)=12 and the RMSS input parameters exactly as in example 2, and compile the executable while linked to both ISAJET and the modified PYTHIA. The resulting mass and mixing spectrum is printed in the PYTHIA output.

Example 4: ISASUSY 7.58 Model
The final example demonstrates how to convert the output of an ISASUSY run using the same SUGRA inputs into the PYTHIA format. This assumes that you already made an ISASUSY run, e.g. with the equivalents of the input parameters above. From the output of this run you can now extract those physical parameters that need to be handed to PYTHIA, in the above example
IMSS(1)=1, IMSS(3)=1, IMSS(8)=0, IMSS(9)=1, RMSS(1)=79.61, RMSS(2)=155.51,
RMSS(3)=533.1, RMSS(4)=241.30, RMSS(5)=10., RMSS(6)=808.0, RMSS(7)=802.8,
RMSS(8)=878.4, RMSS(9)=877.1, RMSS(10)=743.81, RMSS(11)=871.26,
RMSS(12)=569.87, RMSS(13)=803.20, RMSS(14)=794.71, RMSS(15)=-554.96,
RMSS(16)=-383.23, RMSS(17)=-126.11, RMSS(19)=829.94 and RMSS(22)=878.5.