H4l in Full Simulationpreliminary results 2

A. Khodinov* and K. Assamagan**

* State University of New York at Stony Brook** Brookhaven National Laboratory

Data set (signal only)

Z(*)e+e-

Z(*)+-

hZZ(*)

mh = 130 GeV

h4e

h4

h2e2

Framework details

• Number of Events 100.000

• Generator Pythia 6.217 (6.5.0) no filters

• Fully simulated with ATLSIM (6.5.0)• VDC dataset simul_000033• geometry level dc1 ()

• Reconstructed with ATHENA (7.0.2)• Job Options file RecExCommon_jobOptions.txt• Additional MC Truth Spcl_MC (F.Paige and

I.Hinchliffe)

Lepton ReconstructionWe 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)

2. MuID combined (already in the release)Moore + IPatRecRef: 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

Kinematical cuts as in TDR1. e1

+ e2

- or +

- with pT>20 GeV (leading

pair*)

e3+

e4- or

+- with pT>7 GeV (following

pair)

2. Calculate invariant Z mass

m12 = mZ 15 GeVGeV or or (( 6 GeV) 6 GeV)

m34 > 20 GeVGeV

Using these cuts the best result obtained Using these cuts the best result obtained was was =2.1 GeV (MUID Comb)=2.1 GeV (MUID Comb)

We show improvement since our last meeting in NovemberWe show improvement since our last meeting in NovemberWe will show results for HWe will show results for H4e and H4e and H 2e 2 2e 2 also! also!

Additional requirements (Our own)

1. TRD + combinatorial treatmentInstead 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 pTs):

e1+

e2- or

+- with pT>20 GeV min(Mz- Mld)

Doing the above, our best resolution improvesfrom =2.1 GeV to =1.8 GeV (MUID Comb)

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*m0/mll

Where mll is the measured (reconstructed) invariant mass of the 2 leading leptons

Do this before reconstructing the H mass To find m0, we do this on event by event basis:

convolute detector resolution with the Breit-Wigner shape for the Z:

m0 = max ( Gaussian(mll, 0) * BW(mZ,Z) )

where 0 is the detector resolution by plotting mll

without the mass constraint

h4

without mass constraint =1.8 GeV

without mass constraint =2.9 GeV

Leading Mll cut = Mz+-15 GeVMass constraint applied

Improvement from 2.1 GeVto 1.8 GeV with the handingof combinatorial as described

mean 129.9

mean 130.2

mean 130.2

Without mass constraint IPat =2.85 GeV

2.7

Norm calorimeter factor =1/0.9845

MC Isol Cut 5 GeVET cut 15 GeVtrack match YESh2e2

h4e h4e

Leading Mll cut =Mz+-15 GeV

mean 129.9

mean 129.9

mean 129.8

Z (*) +- reconstruction by MuID Comb

Leading Mll cut = Mz+-6 GeV

Mass constraint applied

h4

mean 129.8

mean 130.2

mean 130.2

Leading Mll cut = Mz+-6 GeV

Mass constraint applied

2.7

Norm calorimeter factor =1/0.9845

mean 129.9

mean 129.9

mean 129.9

Problem in calibration forelectrons:

The normalization factor of 1/0.9845 required to restore the 4 momentum of reconstructed electrons

Z (*) e+e-

Summary of our results

Process Reconstructed mean (GeV)

Sigma (GeV)

Muid CB H 4 130.2 1.56

CB + IPat H 2e 129.9 1.89

Ipat H 4e 129.9 1.83

• all the new H4 analyses using Muid CB, we have the best resolution (see the Higgs Working Group meetings)

•Our H2e2 results are in agreement with Wisconsin Group (see the talk Steve Armstrong in the Higg group)

• Our H4e result compare well with Wisconsin result (see the talk by Stathes Paganis : he has worked on electron calibration!)

Summary and plans1. 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 h4e and h2e2)

4. A look at backgrounds: electron, muon isolations5. 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!)