Performance of MET with PU - TIFRindiacms/indiacms-meetings/december-2011/sarany… · 23.12.2011...

Performance of MET with PU

Saranya GhoshEHEP, TIFR

December, 2011

23.12.2011 Performance of MET with PU - S Ghosh 2


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


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


● 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


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)


Momentum spectra

Z→μμ Data samplelog N

In bins of qT and number of primary vertices in event (log scale)


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


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)


Scale for Data and MC overlaid

● Data and MC similar in Plateau region

Z→μμ


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.


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


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


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


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


● 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


For the entire samples

● 50 ns samples give better resolution.● 2ts samples give better resolution.


For events with 5 primary vertices



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.


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


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.


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



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.


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.


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.


Backup Slides


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.


For events with 7 primary vertices



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.


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.


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



● Clear worsening of resolution as number of OOT PU increases● Difference in resolution is smaller than for 50ns 4ts



● Clear worsening of resolution as number of OOT PU increases● Difference in resolution is larger than for 50ns



● Clear worsening of resolution as number of OOT PU increases● Difference in resolution is smaller than for 25ns 4ts


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



● 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



● 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



● 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


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.



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



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



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


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.


Backup Slides


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


● 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


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


Distribution of reconstructed primary vertices for Z→μμ Data sample


qT spectrum of Z→μμ MC sample


Distribution of reconstructed primary vertices for Z→μμ MC

Before reweighting After reweighting


Scale for Z→μμ MC

● Scale is not affected by number of vertices


Resolution for Z→μμ MC

● Resolution becomes poorer as number of vertices increase

Performance of MET with PU - TIFRindiacms/indiacms-meetings/december-2011/sarany… · 23.12.2011...

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