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University of Iowa

qqH qq ZZ qq e + e -  e  e Alexi Mestvirishvili 2005 Fall HCAL Meeting. University of Iowa. H Z Z e + e -  e  e. t t. N . Of Events. CS(fb). 44257. 7.3x10 3. Event generation and reconstruction. PYTHIA 6.2, CMSIM , ORCA version 7.6.0, Pileup.

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University of Iowa

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  1. qqHqq ZZ qq e+e-ee Alexi Mestvirishvili 2005 Fall HCAL Meeting University of Iowa Slide N

  2. H Z Z e+e-ee t t N. Of Events CS(fb) 44257 7.3x103 Event generation and reconstruction PYTHIA 6.2, CMSIM , ORCA version 7.6.0, Pileup Signal events - qqH 300,350 and 500 GeV mass Higgs were generated. No tracker was simulated, e+ e- were selected from generator particle information Higgs and Z decay (forced)modes Background considered in this analysis All cross sections listed here are basically BR decay chain Analysis note submitted CMS AN 2005/014 – In stage of review Presented on HIGGS working group meeting -- good response. Closely working with referees. Slide N

  3. Pre selection cuts • At least two “tracks” with opposite charge, • which then can be Identified as electron/positron • Soft cut on Pt of “tracks” > 10 GeV 1) Iterative cone algorithm Cone radius – 0.5 2) At the preselection stage as jet was Accepted any object found by the jet finder with Et > 20 GeV 3) Jets are well within CMS detector acceptance ||  5 4) No calibration Slide N

  4. Some assumptions VERY PRELIMINARY Main assumption in this analysis is made on the Electron identification and its efficiency. IT IS ASSUMED THAT ELECTRON IDENTIFICATION EFFICIENCY WILL BE AT THE LEVEL OF 94 – 95 % In a region between arrows Falls more than 90% of Electrons, provided selection Cuts are applied on tracks Assumption is based on Many different sources. One of them DC04 data with full track simulation MY STUDY a) Well isolated two opposite charge tracks b) Cut on Et of the tracks etc. Slide N

  5. Missing Et distribution for signal • And background events • H(M=300GeV) • H(M=350GeV) • H(M=500GeV) • t t a) b) c) d) Cuts for leptons and missing ET Leptons (e+ e- ) were selected from generator particles data. Lepton cuts: ||<2.4, ET > 20GeV, |M(e+ e-)-M(Z)|<15GeV, Leptons are between tag jets Cut for reconstructed missing ET > 50GeV Slide N

  6. H(M=300GeV) H(M=350GeV) H(M=500GeV) t t FORVARD JET TAGGING Jets selection Forward jets were searched using rapidity gap method Over all pseudo rapidity range. Jets ET 30GeV – reduces Pileup contamination Jet pairs per event Jet isolation criteria – nothing around the jet in cone 0.5 Jets must be in opposite hemisphere 1 . 2 < 0 Difference between jets Pseudorapidity more than 4.0 If more than one combination of such jets found, jets with largest rapidity difference were accepted as a tagged jets Majority of signal events has At lest one pair of tagged jets If no such combination was Found, event was dropped Slide N

  7. H M=300 – Green points, H M=350 – Red points H M=500 – Blue points, – Black points t t H(M=300Gev) H(M=300Gev) H(M=300Gev) t t FORVARD JET TAGGING Jets Et and di jet mass Di Jet mass distribution for Signal and background events E t of tagged jets Cut is applied at 500 GeV Slide N

  8. Central Jet veto Standard approach: first to find tag jets, then to veto events with additional central jets. First veto events with central jets, than search for tag jest Events with central jets were vetoed before forward jet tagging Pseudo rapidity range -2.0 << 2.0 No need to use b tagging at all Slide N

  9. Signal Significance Signal Significance for different range BUT SIGNAL SIGNIFICANCE IS STILL WELL BELLOW THE ACCEPTABLE 5 LEVEL . Even the background events Are suppressed substantially, Small cross section for signal Events and huge cross section For background is main reason For such low significance. Significance is calculated For 60 fb–1 LHC integrated luminosity Slide N

  10. Results presented on previous slides are for the one particular decay channel H ZZe+e-ee. H and Z’s were forced to decay Through this channels. Taking into account Zboson other decay modes one can extrapolate obtained significance Significance extrapolation Decays considered --- One Z decay to electrons Second Z to any kind of neutrino BUT… Anyway below the 5 level For 60 fb–1 LHCintegrated luminosity Significance is calculated For 60 fb–1 LHC integrated luminosity Slide N

  11. Significance extrapolation Taking into account Z decay to muons electrons And neutrinos -- Very similar Analysis. High efficiency For muon identification (97%) according DAQ TDR Significance is calculated For 60 fb–1 LHC integrated luminosity Extrapolation gives 6 times More events for signal, while background goes up by factor 2. Increase factor for significance is app. 4.26 Could be considered as An upper limit – muon Efficiency is not included Slide N

  12. 300,350 and 500GeV mass Higgs production via VBF with • subsequent decay to ZZ when one Z decays to electron - • positron pair and another to neutrinos, and the tt major • background for this channel were studied. • 2. No b - tagging is necessary, if central jet veto is used • before forward jets are searched and tagged. • 3. Significance for this particular decay channel assuming • 60 fb-1 LHC integrated luminosity is well below acceptable • 5 level. • However, taking into account Z decay modes it could be • possible to have significance around 5 sigma Higgs produced • via WBF and decayed through Z Z for 60 fb-1at low • luminosity condition. SUMMARY Slide N

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