performance of met with pu - tifrindiacms/indiacms-meetings/december-2011/sarany… · 23.12.2011...
TRANSCRIPT
Performance of MET with PU
Saranya GhoshEHEP, TIFR
December, 2011
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Study of the efffects of Pile-Up (PU) on MET with Z→μμ events
● Distribution of reconstructed primary vertices
● Basic Definitions
● Momentum spectra of photons and Zs
● Study on Data samples:
Scale
Resolution
● Comparison of Data and MC
● Effect of instantaneous luminosity on Data and OOT PU on MC\
● Effect of 2ts reconstruction and 25ns BX
Outline
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Distribution of reconstructed primary vertices
May 10 ReReco
Prompt v4
Aug 5 ReReco
Prompt v6
● Significant number of events with high PU
● Mean number of vertices increases slightly with time.
Log scale
Courtesy E Gallo
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● CMSSW_4_2_3
● All figures using PFMET with Type1 corrections
● 3BX average Pile-up reweighting done with respect to the file: Pileup_2011_to_173692_LPLumiScale_68mb.root
Samples, CMSSW & Details
● Z→μμ samples:
MC samples:
➢ /DYToMuMu_M-20_CT10_TuneZ2_7TeV-powheg-pythia/Summer11-PU_S4_START42_V11-v1/GEN-SIM-RECO
● Data samples: /SingleMu/Run2011A
➢ May10ReReco-v1
➢ PromptReco-v4
➢ PromptReco-v6
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Basic definitions
qT : Electroweak boson (Z) or photon (γ) momentum in transverse plane.
uT : Hadronic recoil in the transverse plane.
ul l : component that is parallel to q
T.
ET : Missing Transverse Energy (MET).
Scale factor corrections for MET depends on ET /q
T which is related to l<u
l l>l/q
T or the
'response' .
(Z or γ)
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Momentum spectra
Z→μμ Data samplelog N
In bins of qT and number of primary vertices in event (log scale)
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Z→μμ Data
● Scale is largely unaffected by the number of vertices
● Only minor variations in Scale in the plateau region
Response plots (Scale vs qT) for events with different number of primary vertices
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Resolution plots (scaled RMS of u vs qT) for parallel (left) and perpendicular (right) component of u wrt qT for different numbers of primary vertices
Resolution becomes poorer as number of vertices increase
Z→μμ Data Scaled RMS is the RMS corrected for the Scale (in case Scale is not unity as it is expected to be)
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Scale for Data and MC overlaid
● Data and MC similar in Plateau region
Z→μμ
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Resolution for Data and MC overlaidZ→μμ Samples
● Resolution in data is poorer than in MC● Trend in similar for the different numbers of primary vertices● Smearing of Jets in MC tried in order to account for difference (in following slides)● Note: Observed data-MC differences are not quite consistent among analyzers, and this is under investigation.
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Resolution for Data and MC sample with smearingZ→μμ
An extra smearing factor was applied to PF Jets in MC
thanks to Christian V.
● Reconstructed PF JET associated to generator level jet (ΔR <0.5)● Determine mismeasures energy: δE = Erec - Egen
● Compute smeared reconstructed PF JET energy: Erec
smear = Erec + k.δE● Update PF Jet four vectors and rcompute MET
● Better agreement between Data and MC after smearing● Data still has slightly poorer resolution● Difference is there since smearing does not account for OOT PU● "rhoNeutral reweighting” technique (reweighting MC according to density of neutral particles in event) developed by DESY group to account for this● 3D PU reweighting might improve Data-MC agreement
Uncertainties not used
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Effect of luminosity on MET Resolution
● Scale remains similar● At low qT : Resolution is slightly poorer when luminosity is higher
Events with same number of primary vertices (5 below) but different values of instantaneous luminosity (< and > 1.0 Hz/ub) compared in data samples
Z→μμ Data
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Effect of OOT PU on MET Resolution
Resolution is poorer when OOT PU is higher
Z→μμ MC
Events with same number of primary vertices (5 below) but different number (1-3 vs 4-12) of OOT PU compared in MC sample
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Study of effect of 2ts reconstruction on 50 and 25 ns BX MC samples
●Using 2 time-slices for HCAL energy reconstruction (instead of 4) was proposed to improve MET resolution.
● 4Ts is more sensitive to Out Of Time (late) PU
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● CMSSW_4_2_3 used with updated Type1 corrections for PFMET
● MC samples:
1. S4 50ns : /DYToMuMu_M-20_TuneZ2_7TeV-pythia6/Summer11-HCal_PU_S4_START42_V11-v1/REN-SIM-RECO
2. S4 50ns 2ts : /DYToMuMu_M-20_TuneZ2_7TeV-pythia6/Summer11-HCal_2TS_PU_S4_START42_V11-v2/GEN-SIM-RECO
3. S4 25ns : /DYToMuMu_M-20_TuneZ2_7TeV-pythia6/Summer11-HCal25_PU_S4_START42_V11-v1/GEN-SIM-RECO,AODSIM
4. S4 25ns 2ts : /DYToMuMu_M-20_TuneZ2_7TeV-pythia6/Summer11-HCal25_2TS_PU_S4_START42_V11-v2/GEN-SIM-RECO
● Pile-up reweighting done with respect to the file:
Pileup_2011_to_173692_LPLumiScale_68mb.root
CMSSW, MC Samples & Reweighting Details
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For the entire samples
● 50 ns samples give better resolution.● 2ts samples give better resolution.
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For events with 5 primary vertices
● 50 ns samples give better resolution.● 2ts samples give better resolution.
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Events with 1 to 4 in-time pile-up vertices, 1 to 3 pile-up vertices in the preceding bunch crossing and 0 pile-up vertices in the following bunch crossing
● 50ns samples have better resolution in low qT bins.● For S4 25ns: 2ts sample gives slightly better resolution.
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Events with 1 to 4 in-time pile-up vertices, 0 pile-up vertices in the preceding bunch crossing and 1 to 3 pile-up vertices in the following bunch crossing
● 50 ns samples give slightly better resolution.● 2ts samples give slightly better resolution.● Inconsistency in the 100GeV qt bin
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Events with 1 to 4 in-time pile-up vertices, 1 to 3 pile-up vertices in the preceding bunch crossing and 1 to 3 pile-up vertices in the following bunch crossing
● 50 ns samples give better resolution in most qt bins.● 2ts samples give better resolution.
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Events with 1 to 4 in-time pile-up vertices, 4 to 12 pile-up pile-up vertices in the preceding bunch crossing and 4 to 12 pile-up vertices in the following bunch crossing
● 50 ns samples give better resolution.● 2ts samples give better resolution.
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Conclusions
● For studies od Data and Data-MC comparison
● The scale is more or less independant on the number of vertices.
● Resolution becomes worse as the number of vertices increases.
● Resolution in Data is poorer than the resolution obtained from MC samples.
● Better agreement between Data and MC in terms of resolution when smearing is applied.
● OOT PU causes deterioration of MET Resolution.
● OOT PU and luminosity affect MET resolution along with the number of in-time primary vertices.
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Conclusions
● For 2ts reconstruction studies
● 50ns samples have better resolution that 25ns samples especially when there are pile-up vertices in the following bunch crossing.
● Difference between resolutions for 50ns samples and 25ns samples is larger when the number of pile-up vertices is more.
● The 2ts samples give better resolution than corresponding 4ts samples.
● For 50ns samples: The 2ts sample gives lower resolution only when there are pile-up vertices in the following bunch crossing.
● For 25ns samples: 2ts samples give lower resolution when there are out-time pile-up vertices. Difference is more significant when there are pile-ups in the following bunch crossing.
● Improvement in resolution for 2ts samples is more for events with higher pile-up.
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Continuation
● Work is going on to study MET from generator level information.
● Attempt being made to recreate MET as observed in data after applying various modifications to generator level information in MC such as smearing, thresholds and Pile-Up.
● Study being performed to understand the different effects that affect the observed MET.
Thank you.
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Backup Slides
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For events with 1 primary vertex
● 50 ns samples give better resolution for perpendicular and at low qT for parallel component.● 2ts samples give better resolution.
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For events with 7 primary vertices
● 50 ns samples give better resolution.● 2ts samples give better resolution.
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Events with 0 in-time pile-up, 0 out-time pile-up
● No visible difference between the different S4 samples.
● Expected, since there is no pile-up whatsoever.
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Events with 0 in-time pile-up, 1 to 3 pile-up vertices in the preceding bunch crossing and 1 to 3 pile-up vertices in the following bunch crossing
● 50ns samples give better resolution than the 25 ns samples.● 2ts samples give better resolution.
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S4 50ns 4ts comparison for different PU cases of No PU, 1-3 PU in both previous and following BX, 4-12 PU in both previous and following BX
● Clear worsening of resolution as number of OOT PU increases
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S4 50ns 2ts comparison for different PU cases of No PU, 1-3 PU in both previous and following BX, 4-12 PU in both previous and following BX
● Clear worsening of resolution as number of OOT PU increases● Difference in resolution is smaller than for 50ns 4ts
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S4 25ns 4ts comparison for different PU cases of No PU, 1-3 PU in both previous and following BX, 4-12 PU in both previous and following BX
● Clear worsening of resolution as number of OOT PU increases● Difference in resolution is larger than for 50ns
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S4 25ns 2ts comparison for different PU cases of No PU, 1-3 PU in both previous and following BX, 4-12 PU in both previous and following BX
● Clear worsening of resolution as number of OOT PU increases● Difference in resolution is smaller than for 25ns 4ts
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S4 50ns 4ts comparison for different PU cases of No PU, 1-4 In-Time PU with 1-3 PU in only previous BX, 1-3 PU in only following BX, 1-3 PU in both
● Resolution becomes worse as number of OOT PU increases● Resolution is worse when there is PU in the following BX
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S4 50ns 2ts comparison for different PU cases of No PU, 1-4 In-Time PU with 1-3 PU in only previous BX, 1-3 PU in only following BX, 1-3 PU in both
● Resolution becomes worse as number of OOT PU increases● Resolution is worse when there is PU in the following BX● Difference in resolution appears to be slightly smaller than the 50ns 4ts case
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S4 25ns 4ts comparison for different PU cases of No PU, 1-4 In-Time PU with 1-3 PU in only previous BX, 1-3 PU in only following BX, 1-3 PU in both
● Resolution becomes worse as number of OOT PU increases● Resolution is worse when there is PU in the following BX● Difference in resolution is larger than for 50ns
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S4 25ns 2ts comparison for different PU cases of No PU, 1-4 In-Time PU with 1-3 PU in only previous BX, 1-3 PU in only following BX, 1-3 PU in both
● Resolution becomes worse as number of OOT PU increases● Resolution is worse when there is PU in the following BX● Difference in resolution appears to be slightly smaller than the 25ns 4ts case
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S4 50ns 4ts comparison for different PU cases of No PU, 1-4 In-Time PU with 4-12 PU in only previous BX, 4-12 PU in only following BX, 4-12 PU in
both
● Resolution becomes worse as number of OOT PU increases● Resolution is worse when there is PU in the following BX● Resolution is worst when there is PU in the both BX●In some cases, the resolution for 4-12OOT+ in lower than NO PU. This could be because of low statistics for these events.
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S4 50ns 2ts comparison for different PU cases of No PU, 1-4 In-Time PU with 4-12 PU in only previous BX, 4-12 PU in only following BX, 4-12 PU in
both
● Resolution becomes worse as number of OOT PU increases● Resolution is worse when there is PU in the following BX● Resolution is worst when there is PU in the both BX● Difference in resolution appears to be slightly lesser than the 50ns 4ts case for perpendicular component
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S4 25ns 4ts comparison for different PU cases of No PU, 1-4 In-Time PU with 4-12 PU in only previous BX, 4-12 PU in only following BX, 4-12 PU in
both
● Resolution becomes worse as number of OOT PU increases● Resolution is worse when there is PU in the following BX● Resolution is worst when there is PU in the both BX● Difference in resolution is larger than for 50ns
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S4 25ns 2ts comparison for different PU cases of No PU, 1-4 In-Time PU with 4-12 PU in only previous BX, 4-12 PU in only following BX, 4-12 PU in
both
● Resolution becomes worse as number of OOT PU increases● Resolution is worse when there is PU in the following BX● Resolution is worst when there is PU in the both BX● Difference in resolution between NO PU and PU in both BX appears to be slightly lesser than the 25ns 4ts case
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Conclusions
● 50ns samples have better resolution that 25ns samples when there are pile-up vertices in the following bunch crossing.
● Difference between resolutions for 50ns samples and 25ns samples is larger when the number of pile-up vertices is more.
● For 50ns samples: The 2ts sample gives lower resolution only when there are pile-up vertices in the following bunch crossing.
● For 25ns samples: 2ts samples give lower resolution when there are out-time pile-up vertices. Difference is more significant when there are pile-ups in the following bunch crossing.
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Backup Slides
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Effect of luminosity on MET Resolution
● Resolution is slightly poorer when luminosity is higher
Events with same number of primary vertices (5 or 6 below) but different values of instantaneous luminosity (< and > 1.0 Hz/ub) compared in data samples
Z→μμ Data
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● CMSSW_4_2_3
● All figures for PFMET with Type1 corrections
● MC samples:
/DYToMuMu_M-20_CT10_TuneZ2_7TeV-powheg-pythia/Summer11-PU_S4_START42_V11-v1/GEN-SIM-RECO
● Data samples:
● /SingleMu/Run2011A-May10ReReco-v1/RECO
● /SingleMu/Run2011A-PromptReco-v4/RECO
● /SingleMu/Run2011A-PromptReco-v6/RECO
● Pile-up reweighting done with respect to the file:
Pileup_2011_to_173692_LPLumiScale_68mb.root
CMSSW, MC Samples & Reweighting Details for Z→μμ
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Event Selection Criteria for Z→μμ events
● Events with 2 muons
● Selection criteria on muon:
✔ HLT Isolated muon 17 and HLT Isolated muon 24 triggers used✔ Global muon prompt : tight✔ # of tracker hits > 10✔ # of pixel hits > 0✔ χ2/ndf <10
✔ pT>15 GeV
✔ Isolation criteria : Σ0.3
PTtrack/PT
μ<0.15
✔ δr <0.2 ● Selection criteria for Z:
✔ 70 GeV < Mµµ < 110 GeV
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Distribution of reconstructed primary vertices for Z→μμ Data sample
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qT spectrum of Z→μμ MC sample
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Distribution of reconstructed primary vertices for Z→μμ MC
Before reweighting After reweighting
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Scale for Z→μμ MC
● Scale is not affected by number of vertices
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Resolution for Z→μμ MC
● Resolution becomes poorer as number of vertices increase
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