Sherpa 1.4.3 is installed on Stampede, in the directory /work/02130/ponyisi/sherpa-intel. It is compiled with the Intel compiler with MPI enabled, so it is able to run on (in principle) hundreds of cores simultaneously while generating Feynman diagrams and process grids.
To run Sherpa, create a directory and an appropriate run card in it:
# The following generates p p -> t t~ tau+ tau-
(run){
# ATLAS general parameters
MASS[6]=172.5
MASS[23]=91.1876
MASS[24]=80.399
WIDTH[23]=2.4952
WIDTH[24]=2.085
SIN2THETAW=0.23113
MAX_PROPER_LIFETIME=10.0
MI_HANDLER=Amisic
# Events to generate?
EVENTS = 1000
# Output events in HEPMC format, with this filename prefix
HEPMC_OUTPUT = ttll-hi
# take tau mass into account
MASSIVE[15] = 1
}(run)
(beam){
# beams are protons at 7 TeV each
BEAM_1 = 2212; BEAM_ENERGY_1 = 7000;
BEAM_2 = 2212; BEAM_ENERGY_2 = 7000;
}(beam)
(processes){
# collide light quarks/gluons (93) to top, antitop, tau, antitau, and up to two additional light quarks/gluons
Process 93 93 -> 6[a] -6[b] 15 -15 93{2};
# on shell top -> W b
DecayOS 6[a] -> 5 24;
DecayOS -6[b] -> -5 -24;
# matrix element/showering match with CKKW prescription
CKKW sqr(30/E_CMS)
# enhance rates for final states with seven and eight partons - events will be weighted
Enhance_Factor 2.0 {7}
Enhance_Factor 5.0 {8}
# Factorization/renormalization scales: loose prescription for high multiplicity states
Scales LOOSE_METS{MU_F2}{MU_R2} {8}
# Allow larger error for high multiplicity states
Integration_Error 0.1 {7,8}
End process;
}(processes)
(selector){
# Dilepton mass between 7 GeV and CM energy
Mass 15 -15 7.0 E_CMS
}(selector)
(mi){
# Multiple interactions on
MI_HANDLER = Amisic # None or Amisic
}(mi)