Diapositiva 1

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FxFx merging
in tt+(up to) 2jets
with [email protected]
in PYTHIA8
J. Fernandez
(with many thanks for the
comments and prompt answer
from Josh Bendavid)
Setup and settings (I)
• pp>t t~ +0,1,2j @13TeV generated in separated multiplicity samples
(100k events each) using [email protected] v2.1.1 (No PS):
A.
B.
With FxFx merging option (ickkw=3)
With NO merging option (ickkw=0)
• Same options for the rest:
–
Running options:
•
•
•
•
•
•
–
Jets options:
•
•
•
•
8th April 2014
cteq6_m = pdlabel ! PDF set
average = event_norm ! Normalize events to sum or average to the X
sect.
F
= fixed_ren_scale ! if .true. use fixed ren scale
F
= fixed_fac_scale ! if .true. use fixed fac scale
4 = maxjetflavor
PYTHIA8 = parton_shower
! PS set to OFF in any case
1 = jetalgo ! FastJet jet algorithm (1=kT, 0=C/A, -1=anti-kT)
0.7 = jetradius ! The radius parameter for the jet algorithm
10 = ptj
! Min jet transverse momentum
-1 = etaj
! Max jet abs(pseudo-rap) (a value .lt.0 means no cut)
J. Fernández
2
Setup and settings (II)
• Hadronized with PYTHIA8 (interfaced
through CMSSW_7_1_0_pre7)
– Script provided by Josh Bendavid
– Key parameters:
•
•
•
•
•
•
•
8th April 2014
'JetMatching:coneRadius = 1.',
'JetMatching:qCut = 30.',
'JetMatching:qCutME = 10.',
'JetMatching:nQmatch = 4',
'JetMatching:nPartonsNow = 0', # 1 for 1j, 2 for 2j
'TimeShower:nPartonsInBorn = 2', # 3 for 1j, 4 for 2j
'JetMatching:nJetMax = 1‘ #2 to merge 0j+1j+2j
J. Fernández
3
Some numbers
Process
NNLO
Xsec
(pb)
Frac
Neg
weights
Matching Effective Matching Effective
Eff 1jmax Xsec(pb) Eff 2jmax Xsec(pb)
Gen
CPU
time*
tt0j FxFx
693.0
0.25
0.26
244.7
0.26
244.7
1h
tt1j FxFx
746.4
0.39
0.50
485.2
0.27
262.9
6.5h
tt2j FxFx
600.7
tt0j
NoFxFx
652.3
0.25
-
-
-
-
<1h
tt1j
NoFxFx
715.4
0.40
-
-
-
-
5.6h
tt2j
NoFxFx
656.4
0.41
-
-
-
-
>24h
>24h
*Generation time on a dedicated 32-core multiCPU Xeon. In addition grid process time must be added…
- Xsec values do not match those from Table 5 of arXiv:1405.0301v1 (same ptj value?)
- Many problems running t t + 2j NNLO: 359 subprocesses, some (residual) subprocesses getting stuck
over and over, and crashing after 16h… (P0_gg_ttxgg/GF62, P0_gg_ttxgg/GF61, P0_gg_ttxgg/GF22).
Need them all successfully completed in order to merge properly the full result…
J. Fernández
8th April 2014
4
Caveats for plots
• Gen Jet: any Jet AK4
• Radiated Jet: any Gen Jet not matched
(dR<0.1) to any top decay product
• qCut = 30 GeV
• Two validation checks:
– FxFx merging vs Born level contributions
– FxFx merging vs NoFxFx (simple adding of
histograms according to weights)
• Normalization required to compare same scales
8th April 2014
J. Fernández
5
1 jet Max comparison
8th April 2014
J. Fernández
6
Total number of jets (1jmax)
FxFx
FxFx
NoFxFx
8th April 2014
NoFxFx
J. Fernández
7
Radiated pT>10 jets & pT>30
FxFx
FxFx
1j
2j
NoFxFx
8th April 2014
NoFxFx
J. Fernández
8
1st and 2nd leading jets
FxFx
FxFx
NoFxFx
8th April 2014
J. Fernández
NoFxFx
9
1st and 2nd radiated jets
FxFx
FxFx
30GeV
30GeV
NoFxFx
8th April 2014
NoFxFx
J. Fernández
10
3rd and 4th leading jets
FxFx
FxFx
NoFxFx
8th April 2014
J. Fernández
NoFxFx
11
3rd and 4th radiated jets
FxFx
FxFx
NoFxFx
8th April 2014
J. Fernández
NoFxFx
12
Normalized FxFx vs NoFxFx
FxFx
FxFx
NoFxFx
8th April 2014
J. Fernández
NoFxFx
13
Normalized FxFx vs NoFxFx
FxFx
FxFx
NoFxFx
8th April 2014
J. Fernández
NoFxFx
14
Questions
•
0.7 = jetradius
≠ 'JetMatching:coneRadius = 1.‘
– [email protected] seems to force it to 1. when FxFx is enable in a
warning message but LHE file keeps the 0.7 value
• Grid pack working in 7XY? Using code from [email protected]
independent of CMSSW for the moment
• LHAPDF interface, full or lite?
• CPU time in tt +2j?
• If SIM&RECO CMSSW step fails for some events, are
the weights still valid?
– Should use sum = event_norm instead?
• Differences in xsec obtained wrt those in Table 5 of
arXiv:1405.0301v1
• Cross/section dependes on parton_shower/ickkw
parameters?
8th April 2014
J. Fernández
15
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