FxFx merging
in tt+(up to) 2jets
with aMC@NLO
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 aMC@NLO 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
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NoFxFx
11
3rd and 4th radiated jets
FxFx
FxFx
NoFxFx
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NoFxFx
12
Normalized FxFx vs NoFxFx
FxFx
FxFx
NoFxFx
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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.‘
– aMC@NLO 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 aMC@NLO
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