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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.

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Presentation on theme: "H  4l in Full Simulation preliminary results 2 A. Khodinov * and K. Assamagan ** * State University of New York at Stony Brook ** Brookhaven National."— Presentation transcript:

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

2 Data set (signal only) Z (*)  e + e - Z (*)   +  - h  ZZ (*) m h = 130 GeV h  4e   h  4   h  2e2  

3 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)

4 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

5 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!

6 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)

7 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

8 h4h4 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 

9 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 

10 Z (*)   +  - reconstruction by MuID Comb

11 Leading M ll cut = Mz+-6 GeV Mass constraint applied h4h4 mean  mean  mean 

12 Leading M ll cut = Mz+-6 GeV Mass constraint applied  2.7 Norm calorimeter factor =1/ mean  mean  mean 

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

14 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!)

15 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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