Update on H→ZZ→2l2νν Analysis

Arun KumarUniversity of Delhi

India-CMS Meeting 22nd-23rd Dec. 2011University of Delhi, Delhi

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Introduction and Analysis Strategy

Changes in the analysis since last update

Data/MC comparison for H→ZZ→2e2ν

Trigger Studies for H→ZZ→2e2ν

Results

Summary and Outlook

Outline

I presented the results of H→ZZ→2l2ν analysis in a poster for 1.6 fb-1 luminosity in Hadron Collider Physics Symposium, held in Paris from 14th - 18th Nov. 2011.

Another poster I presented was the results of H→ZZ→2l2q analysis in a poster for 1.6 fb-1 luminosity in Lepton Photon Conference 2011. Conference Report : http://cms.cern.ch/iCMS/jsp/openfile.jsp?type=CR&year=2011&files=CR2011_322.pdf

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Introduction & Analysis Strategy

Motivation: H→ZZ→2l2ν yield is approx. 6 times larger than H→ZZ*→4l so important channel for heavy Higgs (m

H > 250 GeV)

Signal : H→ZZ→2l2ν ~250 GeV < m(H) < ~600 GeV. For m(H) <200 GeV, Z+jets completely dominated.

Backgrounds and Rejection methods: All backgrounds can be reduced by applying cut on MET, ΔΦ(MET,closestJet) , M

T , PT(2l),

m(2l)

Z+jets (Dominant) : Fake MET so Hard cut on MET kills it considerably.

ΔΦ(MET,closestJet) helps in reducing it for lower Higgs masses.

TTbar : anti-b-Tagging & soft muon veto

ZZ→2l2ν (Irreducible)

WZ→3lν : 3rd Lepton Veto

WW→2l2ν : Invariant Mass cut of Z boson

W+jets, QCD are less effective backgrounds and can be controlled easily.

We have shown interest in Electron Studies for this channel like ID comparison and data/MC comparison, Trigger Studies, ttBar estimation and MVA Analysis for this channel. It is shown in the following link:https://indico.cern.ch/getFile.py/access?contribId=6&sessionId=5&resId=0&materialId=slides&confId=130679

PAS : HIG-11-026AnalysisNote: AN2011_407

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Changes in the Analysis since last update

Adjustments in γ+jets method for background estimationOver-estimation of background in 0-jet bin, contamination from real MET sources like (Z+γ , W+γ , W+Jets)Contamination can be reduced by requiring atleast one “soft-jet” in the photon event with pT > 15 GeV

Cut based analysis was retuned using GARCON algorithmOptimize the expected limitOptimization done with larger MC samplesNew working points are mainly tight M

T windows

Parametrization of systematic uncertainity estimate in the optimization procedure has been changed

MT shape-based analysis has been introduced. 10% improvement has been seen in the limits.

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Event SelectionPrimary Vertex: Official Deterministic Annealing Algorithm is used to reconstruct PV PV isNotFake && isValid && ndof >= 4.0 && position.Rho < 2.0 mm && abs(z) < 24 cm

Electron Selection: PT > 20 GeV , |η| < 2.5 Veto electrons in the transition region (1.4442 < |η| < 1.566) VBTF ID (WP80) (detailed cuts in back-up) H/E cut in endcap relaxed to 0.15 to remove inefficiency due to pileup Combined relative isolation < 0.1 (Fast-jet Corrected)

Further Selection: Soft Muon veto : Reject events having muons with pT > 3GeV and reconstructed as TrackerMuon. If pT > 20 GeV then it should be non-isolated. Third Lepton Veto: Reject Event having the third electron with pT > 10 GeV and pass the above ID cuts 76.2 GeV < Inv mass < 106.2 GeV

Preselection = Electron Selection + Further Selection

Pile Up reweighting is done as per the official recipe mentioned on :https://twiki.cern.ch/twiki/bin/viewauth/CMS/PileupMCReweightingUtilities

Beam-Halo and HCAL Noise filters are applied to remove non-collision events.

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Other variables which we cut on are :diLeptonPT, B-Tag discrminator, MET, ΔΦ(MET,closestJet), MT(Trans. Mass of Higgs)

Data/MC comparison Plots at 4.6 fb-1 (1/2)

DiElectronPT [GeV/c]

Fig.6 AN2011_407 Fig.7 AN2011_407

B-Tag Discriminator after PT(ee) > 55 GeV cut

Cuts used:DiElectron PT > 55 GeV ( in earlier update it was 25 GeV)B-Tag Discrm < 2

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Data/MC comparison Plots at 4.6 fb-1 (2/2)Fig.8 AN2011_407 Fig.31 AN2011_407

ΔΦ(MET,closestJet) After Applying MET cut

Fig.34 AN2011_407

MET [GeV]

MT [GeV/c2]

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Background Estimation MC : ZZ,WZ Data Driven : Z+jets, tt~/W+jets/WW

Z+jets : γ+Jets events are used as a control sample to model Z+Jets background.

tt~/WW/W+jets : To estimate the non-resonant background, Z-sideband method with the events in eµ final state is used.

Figure 24. AN2011_407

Table 13. AN2011_407

MET distribution of single photon events and dilepton data

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Trigger Studies for HZZ2l2nu

Data Samples and JSON: /DoubleElectron/Run2011A-05Aug2011-v1/AOD/DoubleElectron/Run2011A-03Oct2011-v1/AOD/DoubleElectron/Run2011B-PromptReco-v1/AOD

S/W : CMSSW_4_2_7_patch3

Tag Selection :

Tag & Probe method is used to calculate the Trigger EfficienciesHLT Path HLT_Ele17_CaloIdT_CaloIsoVL_TrkIdVL_TrkIsoVL_Ele8_CaloIdT_CaloIsoVL_TrkIdVL_TrkIsoVL_v(6-10) ( after Run 170053)

Tag must pass Single Electron Trigger: HLT_Ele27_CaloIdVT_CaloIsoT_TrkIdT_TrkIsoT_v* OR HLT_Ele32_CaloIdVT_CaloIsoT_TrkIdT_TrkIsoT_v*

All cuts are same for Probe except pT and Single lepton trigger requirement

PT > 20 GeVΔR = 0.2

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Trigger Eff. In PT and Eta Bins (1/2)

Probe pT > 20GeVTrigger Eff. is > 99% over whole pT range and whole ECAL fiducial region.

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Results

Figure 53. AN2011_407

Higgs Boson is excluded in the mass range 312 – 455 GeV/c2 at 95% CL

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Service Tasks and Shifts

I am working in ECAL Reco Software Development. First task was : Remove custom logging in favour of LogTrace.

https://savannah.cern.ch/task/?18294 Its been completed and submitted. Following Tags of packages have these changes included in them. These changes are queued for CMSSW_4_4_XRecoEcal/EgammaClusterAlgos V00-06-28RecoEcal/EgammaClusterProducers V00-09-20

I took 3 weeks of ECAL PFG Expert shifts from August 2011 to December 2011. Shifter reports has been shown in weekly ECAL PFG meetings.

https://indico.cern.ch/conferenceDisplay.py?confId=151243https://indico.cern.ch/conferenceDisplay.py?confId=151256https://indico.cern.ch/conferenceDisplay.py?confId=166414

Last Visit : My last visit to cern was from 17th Sept. - 17th Dec. 2011.In my last visit i was involved in following things:

Overall Contribution I took 10 ECAL Online shifts and 5 Online Trigger shifts in CMS control room at P5 in 2010.

Then in 2011, I took 21 Online Trigger Shifts at P5. I took 3 weeks of ECAL PFG expert shifts in 2011. I am also involved in ECAL DPG tasks.

Future work : Second task in hand is : Removal of MyWatcher instances from ECAL Software Signed for Trigger Online shifts for 2012 Run. Signed for 3 weeks of ECAL PFG expert shifts.

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Presented the results of H->ZZ->2l2nu Analysis with full 2011 data and these results

will be published in JHEP. My involvement in this study are: Trigger Studies, Data/MC

comparison and Systematics.

During last CERN visit (17th Sept. 2011 – 17th Dec. 2011) , I took 3 weeks of ECAL

PFG Expert shifts.

Also involved in ECAL Reconstruction Software Development as ECAL DPG task.

Summary

Outlook Plan to apply MVA BDT in this Analysis.

Continue with the ECAL DPG task.

I signed for 21 Trigger Online shifts at CMS Control room.

Also I got 3 weeks of ECAL PFG Expert shifts in the next year.

I also started with H->WW*->l+tau analysis with Ajay Kumar. Will contiue working on it.

I will also be involved in Trigger studies for backgrounds in H->ZZ->2l2nu channel for

February 2012 Trigger Review.

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Thanks

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Back up

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Changes in Gamma+jets method

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Datasets and Software(1/2)Summer 11 MC samples

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Datasets and Software(2/2)

S/W: MC : CMSSW_4_2_X, Global Tag: START42_V13Data: CMSSW_4_2_X, Global Tag: GR_R_42_V19

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Soft Muon Selection

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Pile Up Reweighting

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MC Reweighting for ZZ

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Mass Dependent Selection

Jet Selection PT > 30GeV |η| < 2.4 ΔR with the leptons < 0.5

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Electron Selection

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Background Estimation MC : ZZ,WZ Data Driven : Z+jets, tt~/W+jets/WW

Z+jets : γ+Jets events are used as a control sample to model Z+Jets background. Z+Jets and γ+jets events have similar MET response Also γ+jets events have much larger statistics compared to Z+Jets γ+Jets events are reweighted to match the photon PT shape with Z PT shape Also they are reweighted to match the number of primary vertices. A “mass” is assigned to each photon by sampling from the Z line shape from data γ+Jets yield is normalized to match the Z+Jets yields in data

tt~/WW/W+jets : To estimate the non-resonant background, events in eµ final state passing the full analysis selection are used. A scale factor α is computed from the sidebands (SB) of the Z peak to get the estimate of events in ee/µµ final states. Method can not distinguish between background events and possible signal events in H->WW->2l2ν channel Hence we do not treat H->WW events as a part of the signal when looking for an excess.

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Z+jets Estimation

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Systematics

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Event Yields at 4.6 fb-1

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