Update on H ZZ 2l2ν Analysis

Transcription

1 Update on H ZZ 2l2ν Analysis Arun Kumar University of Delhi India-CMS Meeting 22 nd -23 rd Dec University of Delhi, Delhi

2 Outline 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 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 14 th - 18 th Nov 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 Conference Report : 2

3 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 completely dominated. ~250 GeV < m(h) < ~600 GeV. For m(h) <200 GeV, Z+jets 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 : 3 rd Lepton Veto WW 2l2ν : Invariant Mass cut of Z boson PAS : HIG AnalysisNote: AN2011_407 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: 3

4 Changes in the Analysis since last update Adjustments in γ+jets method for background estimation Over-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 algorithm Optimize the expected limit Optimization done with larger MC samples New 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. 4

5 Event Selection Primary 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 Beam-Halo and HCAL Noise filters are applied to remove non-collision events. Electron Selection: PT > 20 GeV, η < 2.5 Veto electrons in the transition region ( < 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 nonisolated. Third Lepton Veto: Reject Event having the third electron with pt > 10 GeV and pass the above ID cuts 76.2 GeV < Inv mass < GeV Preselection = Electron Selection + Further Selection Pile Up reweighting is done as per the official recipe mentioned on : 5

6 Data/MC comparison Plots at 4.6 fb-1 (1/2) Other variables which we cut on are : dileptonpt, B-Tag discrminator, MET, ΔΦ(MET,closestJet), MT(Trans. Mass of Higgs) Fig.6 AN2011_407 Fig.7 AN2011_407 DiElectronPT [GeV/c] 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 6

7 Data/MC comparison Plots at 4.6 fb-1 (2/2) Fig.8 AN2011_407 Fig.31 AN2011_407 MET [GeV] ΔΦ(MET,closestJet) After Applying MET cut M T [GeV/c 2 ] Fig.34 AN2011_407 7

8 MC : ZZ,WZ Data Driven : Z+jets, tt~/w+jets/ww Z+jets : Background Estimation γ+jets events are used as a control sample to model Z+Jets background. MET distribution of single photon events and dilepton data Figure 24. AN2011_407 tt~/ww/w+jets : To estimate the non-resonant background, Z-sideband method with the events in eµ final state is used. Table 13. AN2011_407 8

9 Trigger Studies for HZZ2l2nu Tag & Probe method is used to calculate the Trigger Efficiencies HLT Path HLT_Ele17_CaloIdT_CaloIsoVL_TrkIdVL_TrkIsoVL_Ele8_CaloIdT_CaloIsoVL_TrkIdVL_Trk IsoVL_v(6-10) ( after Run ) 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 : PT > 20 GeV ΔR = 0.2 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 9

10 Trigger Eff. In PT and Eta Bins (1/2) Probe pt > 20GeV Trigger Eff. is > 99% over whole pt range and whole ECAL fiducial region. 10

11 Results Figure 53. AN2011_407 Higgs Boson is excluded in the mass range GeV/c 2 at 95% CL 11

12 Service Tasks and Shifts Overall Contribution I took 10 ECAL Online shifts and 5 Online Trigger shifts in CMS control room at P5 in Then in 2011, I took 21 Online Trigger Shifts at P5. I took 3 weeks of ECAL PFG expert shifts in I am also involved in ECAL DPG tasks. Last Visit : My last visit to cern was from 17 th Sept th Dec In my last visit i was involved in following things: I took 3 weeks of ECAL PFG Expert shifts from August 2011 to December Shifter reports has been shown in weekly ECAL PFG meetings I am working in ECAL Reco Software Development. First task was : Remove custom logging in favour of LogTrace. Its been completed and submitted. Following Tags of packages have these changes included in them. These changes are queued for CMSSW_4_4_X RecoEcal/EgammaClusterAlgos V RecoEcal/EgammaClusterProducers V 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. 12

13 Summary Outlook 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 (17 th Sept th Dec. 2011), I took 3 weeks of ECAL PFG Expert shifts. Also involved in ECAL Reconstruction Software Development as ECAL DPG task. 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. 13

14 Thanks 14

15 Back up 15

16 Changes in Gamma+jets method 16

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18 Summer 11 MC samples Datasets and Software(1/2) 18

19 Datasets and Software(2/2) S/W: MC : CMSSW_4_2_X, Global Tag: START42_V13 Data: CMSSW_4_2_X, Global Tag: GR_R_42_V19 19

20 Soft Muon Selection 20

21 Pile Up Reweighting 21

22 MC Reweighting for ZZ 22

23 Mass Dependent Selection Jet Selection PT > 30GeV η < 2.4 ΔR with the leptons <

24 Electron Selection 24

25 MC : ZZ,WZ Data Driven : Z+jets, tt~/w+jets/ww Z+jets : Background Estimation 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. 25

26 Z+jets Estimation 26

27 Systematics 27

28 Event Yields at 4.6 fb-1 28

29 29