Transcript Slide 1

V+jets m/e studies with 21X: Status and plans
General EWK Meeting 20-01-09
Christopher Rogan
California Institute of Technology
for
Marcella Bona, Emanuele Di Marco, Ran Feldesh,
Joseph D. Lykken, Paolo Meridiani, C.R., Chiara Rovelli,
Maurizio Pierini, Ilaria Segoni, Maria Spiropulu, Thiago
Tomei, Lukas Vanelderen, Marco Zanetti
◉ goal of the analyses:
◎ candle with the Z mass: validate e and m reconstruction
◎ application examples:
◍ MC tuning with the dN/dnjets and dN/dpT(Z)
◍ check and correction of MET
◍ ratios good for start-up: systematics cancel
◉ references
◎ CMS notes
for 16X analyses:
Z+jets & W+jets Alpgen Validation: CMS AN-2008/091
◉ Z(ee)+jets Candle Analysis: CMS AN-2008/092
◉ Z(mm)+jets Candle Analysis: CMS AN-2008/095
◉ W(en)/Z(ee)+jets Ratio Analysis: CMS AN-2008/096
◉ W(mn)/Z(mm)+jets Ratio Analysis: CMS AN-2008/105
◉
◎
previous EWK talks on 16X analysis:
summary by M.Pierini Nov 11th 2008
◉ note release: E. Di Marco, C. Rogan, and I. Segoni: Oct 17th 2008
◉
◎
V+jets talks:
e and m analyses: I. Segoni and M.Zanetti: Nov 14th 2008
◉ m selection: M. Bona: Nov 28th 2008
◉
V+j so far
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◉ samples: 2.1.X and Fall09
◎ signals, other Z/W decays andtt events: MADGRAPH
◎ QCD: “InclusiveMu15” sample (muon enriched QCD)
◉
general strategy for the analyses
single non isolated muon trigger
muon selection: optimization in the next slides
Z mass window [60, 120] GeV/c2
closest-to-the-leading-muon PV selection
jet clustering (calo jets and track jets: SisCone with 0.5)
with E/pT and h cuts (30/15 GeV and 3/2.4, respectively)
◎ 2D maximum likelihood fit: Z mass and sin(angleMET, MHT)
for Z+jets; transverse mass and sin(angleTS-jet)
◎ floating the shape parameters for low jet multiplicities
and fixing for the high multiplicities
◎ sPlots for verify shapes on data
◎
◎
◎
◎
◎
◉ muon selection in 16X
◎
◎
◎
only global muons
pT > 15 GeV/c
vertex variables and
isolation variables
simultaneous optimization:
◉ vertex variables:
Dxy/s(Dxy) and Dz(m-PV)
◉ isolation variables:
tracking isolation i piT/pmT
ECAL isolation R<0.35 ETECAL
HCAL isolation R<0.5 ETHCAL
◍ extensive study to select the
variables and to establish the
optimization procedure:
done in 16X and now repeated
in 21X production, the PV is
displaced in x so we can calculate
the distance wrt the PV but the
error is calculated wrt (0,0,0)
so we started looking at:
Dxy
better for the electrons that have
typically poorer tracking resolution
about the same discrimination for
muons (wrt the significance)
Hcal isolation:
H0 excluded and
zero suppression introduced
Cut variables
R<0.35 ETECAL
i piT/pmT
Dz(m-PV)
R<0.5 ETHCAL
Dxy
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Optimization on the W selection
 Optimize the Punzi Significance:
 Consider all backgrounds and scan over all cut values
simultaneously, with rates normalized to 100 pb-1
 Consider only events in ML fit ‘signal region’
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R<0.35
ETECAL
<2.25 GeV
R<0.5 ETHCAL
<2.8 GeV
Optimization scans requiring:
i
piT/pmT
<0.15
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Optimization scans requiring:
Dz(m-PV) <0.11 cm
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Dxy(PV) <0.005 cm
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Optimized cut values
Calo jets
Track jets
Values
used
0.15
0.2
0.2
Values
used
0.11
0.11
0.11
2.0
2.0
2.0
3.1
4.5
4.5
0.1
0.11
0.11
0.0045
0.0045
0.0045
(0.11)
2.25
2.75
2.5
(1.6)
2.8
2.8
4.1
4.0
(6.0)
0.11
0.1
0.11
(0.08)
0.005
0.005
0.005
(n.a.)
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Optimized cut values
Calo jets
2.8
Track jets
Values
used
0.2
0.15
0.2
2.25
2.75
2.5
Values
used
0.11
0.11
0.11
2.5
2.0
2.0
2.0
4.5
4.0
2.5
4.5
4.5
0.11
0.1
0.11
0.1
0.11
0.11
0.0055
0.005
0.005
0.0045
0.0045
0.0045
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Changing muon pt cut
W selection
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Changing muon pt cut
Z selection
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Analysis strategy
Common requirements:
Single non isolated HLT trigger (HLT_Ele15_LW_L1R)
pixel-match GSF electron reconstruction
electron identification*
electron isolation*
electron - PV compatibility
calo-jet clustering (SisCone, ΔR=0.5)
electron(s) from W(Z) cleaning from calo-jets
jet counting
* for Z, asymmetric id+iso
W-specific requirements:
Z-specific requirements:
exactly 1 electron (against Z+j)
Z mass veto (decouple W+j dataset from
≥2 electrons (against W+j)
Z+j)
Z mass range (decouple Z+j dataset from
MET > 20 GeV (against QCD)
W+j)
mT(W) > 30 GeV (against QCD)
yields and ratio determination:
Maximum Likelihood fit
efficiency correction of yields, if needed
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why re-iteration with 2.1.X ?
electron reconstruction details changed w.r.t. 1.6.X. (i.e.
CSA07)
tracker material changed
some electron identification related to tracker - ECAL match can
be changed
among others, H/E definition changed
pre-shower is excluded
HO is excluded and zero-suppression in HCAL has been
introduced
H/E is affected
HCAL isolation is affected
PV is displaced in x w.r.t. (0,0,0)
Disclaimer!
In this iteration, possibly no new variables w.r.t. the ones used in
CSA07 analysis are used. Various new quantities have been
developed and released, will be tested in W+j/Z+j @ next round
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Electron identification
We use the set of variables from egamma POG, with selection
depending on electron classification (based on fbrem)
tracker-ECAL
match
ECAL-HCAL match
ECAL cluster
shapes
we compare 2.1.X - 1.6.X and re-optimize selection for golden /
showering both barrel and endcap
this defines the W electron and the first Z electron (i.e. tight)
loose egamma identification on the other (asymmetric ID)
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Efficiency of ele - id
Cuts optimized simultaneously to maximize W signal significance
against QCD
QCD e.m. enriched + b,c→electrons used
The optimized cuts
Single electron efficiency on W+≥0j
selection
ε(CSA07)
ε(Summer08)-*- total eID: 75.5 +/- 0.2 79.0 +/- 0.2
egamma loose
the optimization is driven by W+j. For Z+j, the highest pT electron is
identified with the same criteria to allow efficiency cancelation in Wj/Zj
the ID of the second is based on the same variables, but looser
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S and B yields (W+j)
yields, normalized in 100 pb-1, up to electron definition.
large stat error
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S and B yields (Z+j)
yields, normalized in 100 pb-1, up to electron definition
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Z+jets (MADGRAPH)
m(e+e-) lineshapes
≥1 jet
≥2 jet
≥3 jet
Cruijff = Gaussian + exp tails for signal, parabola for
inclusive bkg
tt+jets (MADGRAPH)
consistent parameters for signal lineshape as a function of jet multiplicity
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mT(W) lineshapes
W+jets
tt+jets
Z+jets
QCD
≥2 jet
≥1 jet
Cafu = Crystal ball + Gaussian with same mean
decreasing importance
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slope correction
e-Slope=6.8±0.5
W/Z = 1.09±0.20
Z+j
e-Slope=7.5±1.2
Yields efficiency-corrected
W+j
Yields uncorrected
e-Slope=6.9±1.1
e-Slope=6.8±0.5
W/Z = 1.01±0.19
⇒ eff changes the slope, but effect on double ratio is within uncertainty
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slope correction
e-Slope=8.0±0.4
W/Z = 0.91±0.05
Z+j
e-Slope=7.32±0.09
Yields efficiency-corrected
W+j
Yields uncorrected
e-Slope=6.82±0.08
e-Slope=7.4±0.3
W/Z = 0.93±0.04
⇒ eff changes the slope, but effect on double ratio is within uncertainty
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◉ for the candle analysis:
◎
we start from the optimization values obtained
for the ratio in the W selection
we can afford to loosen the cut to increase efficiency
◉ muon pT > 10 GeV/c
◉ vertex variables:
Dxy <0.02 cm & Dz(m-PV) <0.15 cm
◉ isolation:
i piT/pmT <0.30 (on the second leg)
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Background
≥1jet
≥1jet
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Signal
≥1jet
≥2jet
≥3jet
≥4jet
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Background
≥1jet
≥2jet
≥3jet
≥4jet
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Signal
≥1jet
≥2jet
≥3jet
≥4jet
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Background
≥1jet
≥3jet
≥2jet
≥4jet
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◉ for the electron candle analysis:
we can afford to loosen the cut to increase efficiency
◉ electron pT > 10 GeV/c
◉ loose electron ID on both legs
◉ Best Z candidate choice (highest pt electrons)
◉ vertex variables:
Dxy <0.04 cm & Dz(m-PV) <0.12 cm
◉ isolation:
i piT/pmT <0.15 (on both legs)
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Signal
≥1jet
≥2jet
≥1jet
≥2jet
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Background
≥1jet
≥2jet
≥1jet
≥2jet
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EXTRA SLIDES
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Madgraph/Alpgen Production changes
 For tt+j
 parton pt 20, matched at 30 MADGRAPH – KT MLM matching
x-section 317pb @ 10 TeV, x-section 750 pb @ 14 TeV
 Parton pt 70, matched at 20 GeV, ALPGEN –MLM (old, IC) Matching
x-sec 450 pb @14 TeV – if 20 GeV parton pt x-sec
754 pb@14 TeV,
x-section 270 pb@ 10 TeV [15% compared to MAD, MAD>ALPGEN
but different scales, PDFs see below]
 Scale (m_top)^2 at MADGRAPH
 Scale (M_T)^2=sum(m_top^2+P_T^2) ALPGEN
Lower Q^2 pushes the cross section up (MAD>ALPG) (10%)
 PDF CTEQ6L NLO and corresponding a_s change in MADGRPAH
 PDF CTEQ5L LO ALPGEN
NLO PDF pushes x-section up (MAD>ALPG) (10%)
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Comparison of isolation variables: CSA07 - FALL08
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Comparison of vertex variables: CSA07 - FALL08
significance
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isolation variables:
tracking isolation
normalized:
i piT/pmT
ECAL isolation: R<0.35 ETECAL
HCAL isolation: R<0.5 ETHCAL
◉
tracking isolation:
tracks within DR < 0.5
◈ at least 5 associated hits
◈ |Dz(track-PV)| < 0.1
cm
|Dxy/s(Dxy)| < 5
◈ 500 MeV/c < pT < 500 GeV/c
◈
ECAL isolation: EM
calotowers in the 0.35 cone
around the m
m energy is not subtracted
HCAL isolation: hadronic
calotowers in the 0.5 cone
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W selection efficiencies
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Z selection efficiencies
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Eseed/Pout
Major point: track pout estimation depends by the tracker
material knowledge
barrel
endcap
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Δηvtx
GSF-track - ECAL supercluster match
larger tails for non-showering
non-showering endcap bumps for η>0, η<0: tilt changed in the
geometry?
barrel
endcap
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ΔΦvtx
GSF-track - ECAL supercluster match
barrel
endcap
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H/E
CSA07: H/E = sum(H rechits) / supercluster energy in cone
ΔR=0.1
no HCAL zero-suppression
Summer08: H/E = max (H rechit / basic cluster ), the H rechit is
the one above the ECAL basic cluster
HCAL zero - suppression
barrel
endcap
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s9/s25
Cluster shape variable
barrel
endcap
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σηη
Cluster shape variable (cluster width)
changed thresholds?
barrel
endcap
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R<0.35
ETECAL
Dz(m-PV)
R<0.5 ETHCAL
i
piT/pmT
Dxy(PV)
Optimization scan requiring:
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R<0.35
ETECAL
Dz(m-PV)
R<0.5 ETHCAL
i
piT/pmT
Dxy(PV)
Optimization scan requiring:
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R<0.35
ETECAL
Dz(m-PV)
R<0.5 ETHCAL
i
piT/pmT
Dxy(PV)
Optimization scan requiring:
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Optimization
 Some comments:
 Currently we are not including a sphericity cut or MET cut in the
optimization (we will include this once I finish the W MET calibration
using the Z candle)
 As a result, we are cutting more tightly on these five variables
relative to what we will do when including MET or sphericity - I
anticipate that the signal efficiency will go up with
 Ultimately, we will also do the optimization in the signal region of
the ‘angular variable’ which we use in the fit - we can’t do this until
we have the W MET calibration.
 Hence these are probably not the ‘final’ values, but they
demonstrate the procedure/philosophy of the optimization
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what looks different
Most of the electron ID variables looks very similar to CSA07.
(see backup)
larger differences in: H/E, σηη
H/E: definition changed, was H/E in a cone ΔR=0.1, now is HoverECALseed/Eseed
σηη: noise threshold for covariance matrix calculation changed
(w0=4.2 → 4.7): expected larger width
σηη
barrel
H/E
barrel
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what’s looks different: Δηvtx
double peak for golden (i.e. when the super-cluster = 1 basic
cluster) in the endcap
peak>(<)0 for η<(>)0
true also evaluating Δη=ηclus-ηgenele
it is a cluster problem
difference 1.6.X - 2.1.X:
2.1.X has not the preshower: the cluster position
(depth in crystal) accounts for it with a parameter
hypothesis check. In 3.0.X preshower is back
Δηvtx(3.0.X)
ηclus-ηgenele
the double peak disappears
η
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electron isolation
Comparison of the variables used in the CSA07 notes
Traker: sum(pTtracks)/pTele , with internal cone veto
internal cone veto found to be good and robust
external cone ΔR=0.4: all similar, chosen the
intermediate one
ECAL: sum(ET5x5 crystals-ETsuper-cluster)/ETsuper-cluster in a cone
ΔR=0.4
electron footprint ETsuper-cluster not optimal, move to
rechits
isolation
soon
tracker
veto cone
ECAL
rechits
removal
HCAL: sum(ETrechits)/ETsuper-cluster in a cone ΔR=0.4
See summary from M. Le Bourgeois:
http://indico.cern.ch/contributionDisplay.py?contribId=4&confId=4
3146
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isolation: distributions
tracker
HCAL
ECAL
ε(CSA07)
isolation
*- tracker:
*- ECAL:
*- HCAL:
91.8 +/- 0.4
90.3 +/- 0.4
93.6 +/- 0.4
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ε(Summer08)-
89.025 +/- 0.294.748 +/- 0.291.989 +/- 0.2
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vertexing variables
Used to suppress events not coming from Primary Vertex
(PV):
dz = zele-zPV
dxy = distance in transverse plane w.r.t. PV
RMS=210μm
RMS=66μm
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jet multiplicity dependency (1)
-estimate on Fall08 samples with HLT
efficiency variations in different multiplicities change the slope V+(n-1)j /
V+(n)j
but mostly cancels out in double ratio W+nj / Z+nj (W ele and 1st ele of Z
have the same selection)
Z+jets: no variations at all
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jet multiplicity dependency (2)
re-estimate on Fall08 samples with HLT
W+jets: 2% drop at each added jet
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maximum likelihood fit
signal, backgrounds yields extracted on data with extended,
maximum likelihood fit
for Z+≥1jet also Z lineshape parameters extracted on data
Z+jets:
1dim fit: P=PDF(mee)
total number of events
entering the fit
(i.e. extended likelihood)
W+jets:
1dim fit: P=PDF(mTW)
Ni=signal and backgrounds yields
Z+jets: i=signal, tt
W+jets: i=signal, tt+QCD, Z+jets
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Tracking Isolation i piT/pmT
comparison
wrt the jet bin
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ECAL Isolation R<0.35 ETECAL
comparison
wrt the jet bin
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HCAL Isolation R<0.5 ETHCAL
comparison
wrt the jet bin
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vertex variable: Dz(m-PV)
comparison
wrt the jet bin
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vertex variable: Dxy
comparison
wrt the jet bin
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W selection results
Calo jets
16X numbers: CAVEAT
different cuts
and different energy!
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W selection results
Track jets
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Z selection results
Calo jets
16X numbers: CAVEAT
different cuts
and different energy!
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Z selection results
Track jets
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W slopes
Calo jets
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W slopes
Track jets
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Z slopes
Calo jets
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Z slopes
Track jets
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Calo jets
Track jets
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W/Z Ratio
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