Higgs & Top at LHeC

Monday 24 Apr 2017, 11:00 → 13:00 Europe/Zurich

CERN

CERN - Tokyo - Liverpool - Johannesburg - Beijing - Hamburg

Satoshi made a short presentation on the comparison of invisible search with delphes_card_FCCeh_PK_final.tcl(3.4.0) and delphes_card_FCCeh_PK.tcl(3.1.2).
The sensitivity is essentially the same (cut-based: 2.75%, MVA: 2.41% for 1ab--1 of FCC-he).
Uta mentioned that we are as good as FCC-hh detector.

Uta reminded about the problem with Pythia 8 on generating NC DIS.

Orhan showed slides about MadGraph5+Pythia8+DIRE setup, generating NC DIS events.
Uta asked to use the HERA frame to avoid confusion.

11:00 → 11:10 Update on invisible decay study

Speaker: Satoshi Kawaguchi (Tokyo Institute of Technology (JP))

April_24th.pdf

11:10 → 11:20 Hbb coupling measurement

Speaker: Masahiro Tanaka (Tokyo Institute of Technology (JP))

11:20 → 11:30 Liverpool studies

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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Message Body
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.

Speaker: Uta Klein (University of Liverpool (GB))

I will comment of Pythia8 mysteries

11:30 → 11:40 H to phiphi to 4b

Speaker: Mr Chen Zhang (Peking University)

11:40 → 11:50 Status of RPC SUSY

Speaker: Dr Kechen Wang (DESY / IHEP)

11:50 → 12:00 Status of Wits Studies

Speakers: Mukesh Kumar (University of the Witwatersrand (ZA)), Xifeng Ruan (University of the Witwatersrand (ZA))

12:00 → 12:10 FCNC top-Higgs couplings

Speaker: hao sun (DaLian University of Technology)

12:10 → 12:20 Top-q-gamma FCNC

Speaker: Orhan Cakir (University of Ankara (TR))