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MIT 8 882 - Higgs Analysis – Details

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Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 278.882 LHC PhysicsExperimental Methods and MeasurementsHiggs Analysis – Details[Lecture 25, May 11, 2009]C.Paus, LHC Physics: Higgs Analysis - Details 2Organization Project 3●should be complete by now.... Course evaluation●please fill in the Web forms at: http://web.mit.edu/subjectevaluation/●high participation would be very desirable Conference●all set for May 19 at 12:00am in 26-528Final Conference Project LHC Physics: “Experimental Methods and Measurements” Plenary Session (12:00–13:30, May 19, 26-528)●Welcome and LHC Overview (C.Paus)●Search for Standard Model Higgs Boson: Overview (M.Klute)●Search for Higgs in H→ZZ* (M.Chan)●Search for Higgs in H→WW* (H.Gray)C.Paus, LHC Physics: Higgs Analysis - Details 4Lecture Outline Higgs Analysis – Details●Higgs Searches in the Standard Model●Search for Higgs in H→ZZ* ●Search for Higgs in H→WW*●( Search for Higgs in qqH→WW* ) Analysis information will be complete●each analysis TWiki has detailed instructions●signal and background samples are completely copied●new updated analysis examples are providedC.Paus, LHC Physics: Higgs Analysis - Details 5Standard Model Higgs Search Conference organization●there is an overall introductory talk●for the Standard Model Higgs analyses there is a specific overview presentation (?)●idea: no presentation afterwards explains theory/general again●theory of Standard Model Higgs (1/2 slide)●theory constraints on its mass●explain status of the Standard Model Higgs searches before LHC●what else do we know about the Standard Model Higgs? radiative corrections, electroweak data●what can we expect from the LHC?C.Paus, LHC Physics: Higgs Analysis - Details 6Analysis: Generic Instructions Two different types of analyses●pure Higgs search in a given channel●make mass plot●optimize selection cuts to get the “best” mass plot●number of signal and background event●signal significance●luminosity needed to make 5 standard deviation discovery●identify of Vector Boson Fusion (VBF) Higgs production●tag a forward jet●measure forward jet tagging efficiency with Monte Carlo info●measure rate of gluon fusion Higgs events passing forward jet tag●extract ratio of gluon fusion and VBF Higgs events after before and after the forward jet tagC.Paus, LHC Physics: Higgs Analysis - Details 7Analysis: Overview New with respect to previous projects●there is no data yet●I doubt we could be easily allowed to use it if this was next year●so we have to use Monte Carlo●which of course has a Higgs signal●Monte Carlo description is complete●signal has various mass assumptions [GeV]: 130, 140, 150 .... ●full background description also given●only real leptons are properly covered●does not include complete 'fake' leptons●needs to be tested and adjusted to data●substantial amount of work●main background sources: multi-bosons to leptons (WW, WZ, ZZ)●fakes come from heavy quark decays, usual QCD events, ....C.Paus, LHC Physics: Higgs Analysis - Details 8Analysis: Overview, continued Outline of analysis sequence●more complex than other projects before●step 0: look at general analysis selection code and tune cuts as needed●step 1: submit condor jobs to produce histograms for each Monte Carlo contribution●step 2: merge all Monte Carlo contributions●sometimes there are several files per Monte Carlo contribution●simple root function used: hadd, but combined in script●step 3: make plot and determine number of events from each Monte Carlo contributionC.Paus, LHC Physics: Higgs Analysis - Details 9Analysis: Install Software Unfortunately CMS has another software ●login to MIT cluster at CERN●login to MIT cluster at CERN: ssh pcmit00.cern.ch●only from CERN machine: for externals pass through lxplus.cern.ch●use tar ball: ~paus/cms.tgz●cd ~/; tar fzx ~paus/cms.tgz●setup the CMS software●cd ~/8.882/cms; source INIT●ready to go to the next stepC.Paus, LHC Physics: Higgs Analysis - Details 10Analysis: Creating PrimitivesCommon analysis primitives are prepared●separate muon and electron identification●large number of criteria used●optimal point tricky to choose: high efficiency but little fake●optimal point analysis dependent: full optimization required●often similar id requirements are nevertheless used●also photon, tau, jet and met ids are applied●after Id phase various objects have to be 'cleaned' ●jets should not contain identified muons to avoid double counting●merging phase to collate the identified objectsSee examples●~/8.882/cms/root/runHww.C ●~/8.882/cms/root/runHzz.CC.Paus, LHC Physics: Higgs Analysis - Details 11Analysis: H → WWObjects to consider●Higgs decays to 2 W bosons●each W boson decays leptonically●muon + neutrino or electron + neutrino●two lepton types bring a number of coding complications with it●basic observables●2 leptons: muon/muon, electron/electron, muon/electron●missing ET in the event●form approximation of Higgs mass: transverse mass●peaks at real Higgs mass but has a long tail●check documentation on Jacobian peak for W boson mass measurement●already done in the selection code for you●observation is counting experiment: signal vs backgroundC.Paus, LHC Physics: Higgs Analysis - Details 12Analysis: step 0 – adjust selection WW analysis: MitHiggs/HwwMods/*/HwwExampleAnalysisMod.*●histograms are booked here●check what they are, add what you would like to look at●selection details (~optimal), total of nine cuts applied●presel: highest lepton pT > 20, lowest lepton pT > 10, MET > 30, dilepton mass > 12●number of central jets (<1)●MET (min < MET < max, depends on final state)●delta phi between leptons (<max, depends on final state)●dilepton mass (<max, depends on final state)●highest lepton pT (min < pT < max, depends on final state)●lowest lepton pT (>min, depends on final state)●dirty muons (<1)●clean extra tracks (<4)C.Paus, LHC Physics: Higgs Analysis - Details 13Analysis: H → ZZ Objects to consider●Higgs decays to 2 Z bosons●each Z boson decays leptonically●muon + muon or electron + electron●two lepton types bring a number of coding complications with it●basic observables●3 permutations:


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