The order of producing cross section for SUSY decays

FCCSW
1

Dear all,

I am wondering at which level of accuracy the Pythia8_EDM4Hep will produce root files and the cross-section for SUSY decays. Is it at LO or at higher order like NLO? Because I would like to get root files at higher orders.

My Pythia card to produce events for stop-pair production is like the following:

! 1) Settings used in the main program.
Random:setSeed = on
Main:numberOfEvents = 15000 ! number of events to generate
Main:timesAllowErrors = 5 ! how many aborts before run stops

! 2) Settings related to output in init(), next() and stat().
Init:showChangedSettings = on ! list changed settings
Init:showChangedParticleData = on ! list changed particle data
Next:numberCount = 100 ! print message every n events
Next:numberShowInfo = 1 ! print event information n times
Next:numberShowProcess = 1 ! print process record n times
Next:numberShowEvent = 0 ! print event record n times

! 3) Beam parameter settings. Values below agree with default ones.
Beams:idA = 2212 ! first beam, p = 2212, pbar = -2212
Beams:idB = 2212 ! second beam, p = 2212, pbar = -2212
Beams:eCM = 100000 ! CM energy of collision

! 4) Read SLHA spectrum (a few examples are provided by default)
SLHA:file = S.spc1333
#SLHA:useDecayTable = on

! 5) Process selection
SUSY:all=on

! Optionally select only specific sparticle codes in the final state
SUSY:idA = 1000006 ! 0: all ! in our case the final susy particles are stop-pair
SUSY:idB = 1000006 ! 0: all

!set the decay mode of the stop → top X0
1000006:onMode = off
1000006:onIfAny = 6 1000022

!set the decay mode of the top → W b
6:onMode = off
6:onIfAny = 24 5

!set the decay mode of the W → electron X0
24:onMode = off
24:onIfAny = 11 13

! 6) Settings for the event generation process in the Pythia8 library.#
PartonLevel:MPI = on ! no multiparton interactions
PartonLevel:ISR = on ! no initial-state radiation
PartonLevel:FSR = on ! no final-state radiation
HadronLevel:Hadronize = on ! no hadronization

Thank you so much in advance!
Best regards,
Safura

2

Dear Safura,

Thank you for your post.

The framework ‘just’ provides a binding to Pythia8 which means that you get whatever Pythia8 generates with the card you provide. In this regard, the question would better fit a Pythia8 forum.

That being said, Pythia8 is a LO program so I think you would have to go for an alternative solution to achieve what you need. The framework can read HepMC format which means that you can generate your truth level dataset outside with any generator supporting this data format (e.g. aMC@NLO + Pythia) and load the output into your Gaudi configuration.

I hope this helps,
Brieuc

3

Dear Brieuc,

Thank you so much for your nice response!

Best
Safura