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H 4l in Full Simulation preliminary results 2 A. Khodinov * and K. Assamagan ** * State University of New York at Stony Brook ** Brookhaven National Laboratory

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Data set (signal only) Z (*) e + e - Z (*) + - h ZZ (*) m h = 130 GeV h 4e h 4 h 2e2

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Framework details Number of Events GeneratorPythia (6.5.0) no filters Fully simulated with ATLSIM (6.5.0) VDC dataset simul_ geometry leveldc1 ( ) Reconstructed withATHENA (7.0.2) Job Options fileRecExCommon_jobOptions.txt Additional MC TruthSpcl_MC (F.Paige and I.Hinchliffe)

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Lepton Reconstruction We suppose to compare 2 alternative methods matching tracks in the Inner Detector with Muon Spectrometer. 1. STACO (statistical combination) MuonBox + Xkalman ( planned to be included in the ATLAS software release. When?). so currently use ONLY MuonBox Ref: Muon reconstruction with Muonbox and STACO by Hassani, S. (Saclay)Hassani, S. 2. MuID combined (already in the release) Moore + IPatRec Ref: Muon reconstruction with Moore and MuID by Biglietti M., Cataldi G. (Naples University, INFN Lecce) STACO & Muid Comb: Combination of the muon system and the inner detector tracks “MuonBox” & “MuidStandAlone” : Back tracking of the MuonBox and MOORE tracks to the interaction point

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Kinematical cuts as in TDR 1.e 1 + e 2 - or + - with p T >20 GeV (leading pair*) e 3 + e 4 - or + - with p T >7 GeV (following pair) 2. Calculate invariant Z mass GeV or ( 6 GeV) m 12 = m Z 15 GeV or ( 6 GeV) GeV m 34 > 20 GeV Using these cuts the best result obtained was =2.1 GeV (MUID Comb) We show improvement since our last meeting in November We will show results for H 4e and H 2e 2 also!

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Additional requirements (Our own) 1.TRD + combinatorial treatment Instead of taking just the 2 hardest leptons as the leading pair, we look though all the possible 4 lepton combinations for the leading and following pairs but retain the combination where the leading pair is best reconstructed (we do not require hardest p T s): e 1 + e 2 - or + - with p T >20 GeV min(M z - M ld ) Doing the above, our best resolution improves from =2.1 GeV to =1.8 GeV (MUID Comb)

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Additional Requirements our own 2. Z-mass constraint Assuming the 2 leading leptons come from an on-shell Z of mass m0, rescale the lepton 4-momentums such that: p p*m 0 /m ll Where m ll is the measured (reconstructed) invariant mass of the 2 leading leptons Do this before reconstructing the H mass To find m 0, we do this on event by event basis: convolute detector resolution with the Breit-Wigner shape for the Z: m 0 = max ( Gaussian(m ll, 0 ) * BW(m Z, Z ) ) where 0 is the detector resolution by plotting m ll without the mass constraint

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h4h4 without mass constraint =1.8 GeV without mass constraint =2.9 GeV Leading M ll cut = Mz+-15 GeV Mass constraint applied Improvement from 2.1 GeV to 1.8 GeV with the handing of combinatorial as described mean mean mean

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Without mass constraint IPat =2.85 GeV 2.7 Norm calorimeter factor =1/ MC Isol Cut 5 GeV E T cut 15 GeV track match YES h 2e2 h 4e Leading M ll cut =Mz+-15 GeV mean mean mean

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Z (*) + - reconstruction by MuID Comb

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Leading M ll cut = Mz+-6 GeV Mass constraint applied h4h4 mean mean mean

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Leading M ll cut = Mz+-6 GeV Mass constraint applied 2.7 Norm calorimeter factor =1/ mean mean mean

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Problem in calibration for electrons: The normalization factor of 1/ required to restore the 4 momentum of reconstructed electrons Z (*) e + e -

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Summary of our results ProcessReconstructed mean (GeV) Sigma (GeV) Muid CB H 4 CB + IPat H 2 e Ipat H 4e all the new H 4 analyses using Muid CB, we have the best resolution (see the Higgs Working Group meetings) Our H 2e2 results are in agreement with Wisconsin Group (see the talk Steve Armstrong in the Higg group) Our H 4e result compare well with Wisconsin result (see the talk by Stathes Paganis : he has worked on electron calibration!)

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Summary and plans 1. MuID combined provides better resolution than MuId stand alone, so we are awaiting for STACO to implement into the analysis. 2. Photos + filters on is required to simulate Brem properly (Pythia itself does not provide right Brem) and increase the statistics of ‘good’ reconstructed Higgs bosons. 3. Analysis tuning is planned (mostly h 4e and h 2e2 ) 4. A look at backgrounds: electron, muon isolations 5. We will obtain and use the electron calibration done recent by the Wisconsin Group (see the talk by Stathes Paganis in the Higgs Working Group!)

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