Pythia8 versus Pythia-6-Dis-modified
From Uta KleinAdd contact
To Lhec-phys-higgs TopAdd contact
Date 2017-04-12 17:19
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Dear All,
I had a quick look at the default Pythia8 installation.
In particular, I checked the NC DIS process
define j = g u d s c b u~ d~ s~ c~ b~
define p = g u d s c b u~ d~ s~ c~ b~
generate p e- > j e- j
for some pt>6.5 GeV cuts for all particles species (jets, electrons, photons)
For technical reasons I was using 2 slightly different MG5 versions,
but as tested multiple times, this doesn't matter, and I got the same cross section of 1.33*10^4 pb for both versions (so another check)
I was always using Delphes 3.4 and the FCC-eh detector.
Here the comparison on Delphes-level
Pythia8 Pythia6-Dis-modified
jetsize 2.266 2.448
eta-jet 3.495 1.165 -> the distributions look totally different,
and 'ill' for Pythia8 (like 'ears' of a hare, nothing central)
pt-jet 10.76GeV 11.22GeV
el-size 4860 5000
eta-el 1.527 -1.806 -> looks totally wrong for Pythia8
MET> 7.256GeV 2.539GeV -> about factor 2 higher for Pythia8
So, although nominal Pythia8 has a survival rate of 4860 out of 5000 events (our Dis modified Pythia has 5000 out of 5000), for me it looks like that something is going wrong and may need a further adjustment for a pe-collider.
Please let me know your observations. The kinematics for NC-pe DIS can be easily checked. Jets have to be more central/forward (0 to +eta ranges) while electrons are scattered backwards (-eta range) - at least for the small pT-jets that I was using here.
Any other observations?
Thanks and cheers, Uta.