Underlying event settings
This is a quick look at how the underlying event multiplicity changes with
pt-min (PARP(82)) in PYTHIA to see what to how to change UE settings to look
at how robust jet reconstruction is in di-jet and gamma-jet events.
The events were generated with PYTHIA 6.323 using the underlying event
settings given on the web:
* pythia tune for current ATLAS pythia
MSTP(68)=1
MSTP(70)=2
MSTP(82)=4
*def PARP(82)=2.6
PARP(82)=2.0
PARP(84)=0.3
PARP(90)=0.24
MSTJ(11)=3
MSTJ(22)=2
PARJ(54)=-0.07
PARJ(55)=-0.006
MSTP(128)=1
MSTP(52)=2
MSTP(54)=2
MSTP(56)=2
MSTP(51)=10042
MSTP(53)=10042
MSTP(55)=10042
10k events were generated for MB jet settings:
* setup mb events
MSEL=0
MSUB(11)=1
MSUB(12)=1
MSUB(13)=1
MSUB(28)=1
MSUB(53)=1
MSUB(68)=1
MSUB(94)=1
MSUB(95)=1
MSUB(96)=1
Some particles were made stable and this will introduce a small change
in the multiplicity.
* make some particles stable: pi0, Ks, Lambda0
MDCY(PYCOMP(111),1)=0
MDCY(PYCOMP(310),1)=0
MDCY(PYCOMP(3122),1)=0
The underlying event was defined based on the CDF analysis (ref CDF). The
particle distribution relative to the leading jet axis (this was
defined using the simple PYTHIA cone algorithm-PYCELL) was plotted for
rapidity<1. The multiplicity in the underlying event
region was then taken as the multiplicity in the region 60-120degrees
relative to the jet axis.
The results are given in:
* Name: Craig Buttar
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