SCALUP and shower_scale_factor in NLO simulation
Dear MG5 team,
May I know how shower_scale_factor in run_card of NLO simulation works in detail?
It looks like first setting min and max scale for this from subroutine assign_scaleminmax in Template/
xscalemin = max( shower_scale_factor * 0.1 * HT/2 , 10.0)
xscalemax = min( max( shower_scale_factor * 1.0 * HT/2, xscalemin + 20.0 ), 2 Sqrt( E_beam1 * E_beam2 ) )
subroutine set_shower_scale in Template/
S-event
SCALUP = min( xscalemax, shower_S_scale )
H-event
SCALUP = min( xscalemax, max( shower_H_scale , ref_H_scale - min (emsca, xscalemax) )
shower_S_scale and shower_H_scale seem to be a kT distance between two partons which will be merged at next step in kt clustering when I check subroutine set_shower_
The question is: if there is a light-parton in S-event, for example, p p > t t~ j [QCD] and j have smaller pt than HT/2, then does shower_scale_factor do nothing when we generate showering?
I guess this is related to aMC@NLO matching part in pythia8 but I want to make sure.
Best wishes,
Sung Hak
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- Paolo Torrielli Edit question
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