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Electron reco and identification

improvements for 17.2 rel & HZZ analysis

Fany Dudziak

ISU group meetingFocus Talk - June 4th 2012

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Introduction• New electron reconstruction in 17.2• New electron PID dedicated to the HSG2 analysis• Cross checks about misalignments effects on the

new track match• Δη and Δφres

• What about adding a new electron category to handle the conversions ?

• Big summary

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The new electron reconstruction : rel 17.2

• Big effort since few years to improve the electron reco

• Miss an efficient brem fit : GSF has been chosen (efficient, « CPU reasonable »)

• Studies about the track to cluster matching (my thesis)

way of improvement

• Both are used in the new reco

• Before 17.2 : 2 kinds of electrons:• el_pt …• el_GSF_pt

• Now only el_pt but THEY ARE GSF

• We need a new electron Identification corresponding to this new reco.

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Motivations for the new reco

Track reco efficiency

Fraction of radiated energy in the ID vs

eta

• Lot of material in the ID high brem effect mainly at large eta(projectif)

• The track reco suffers from the brem + affects the pt measurement + bigger losses at low pt + big ambiguity between electron/photon + charge misidentification

• Brem fit refitted the track surching for kicks in the path, and estimating the energy loss

Very CPU consuming Not used for the trigger !!

• Add the Δφres to improve again

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Importance of low pt electron in the HZZ4l analysis

ET1

ET5 ET4

ET2

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Reminder about the Δφ rescaled

• Δφ(track - calo_s2) extrapolated from perigee, P rescaled to the E_cl (much less sensitive to brem)

minbias minbias

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Impact of the new reco

Old reco (17.0)GSF without ΔφresGSF + Δφres (17.2)

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Impact of the new reco

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The MultiLepton Menu (I)

• Reconstruction/egamma/egammaAnalysis/egammaAnalysisUtils/trunk/Root/MultiLeptonDefs.cxx

• Dedicated to multilepton analysis involving low pt electrons

• Separation in 2 categories of electrons : low brem and high brem (as we have the information from GSF)

• Goal:• Flat ID efficiency vs eta, pt, and pile-up, wrt the reconstructio• Better rejection of fakes (hadrons, photons) than the loose++ ID but with similar

efficiency.• Robust wrt to pile-up.

bool passMultiLepton (double eta, double eT,double rHad, double rHad1, double Reta, double w2,  double f1, double f3, double wstot, double DEmaxs1, double deltaEta, int nSi, int nSiDeadSensors, int nPix,int nPixDeadSensors, double deltaPhiRes, double dpOverp, double TRratio, int nTRTTotal,int nBlayerHits, bool expectBlayer, bool debug  )

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The MultiLepton Menu (II)

• Giacomo Artoni and Kate Wahlen are the student who wrote the menu

• I was asked by Christos to do some checks, as I already did on the first data • Check on the track info :• With GSF no more outlier hits, but now we have the

deadSensorHits info should we use that? Answer is yes :

• Nothing important on efficiency or rejection, just independant from detector condition

Efficiency wrt container (no cut)

Iso electron

Bkg electron

hadrons

nPixHits++nSCTHits>=7 99.15% 60.80% 89.55%Idem + Dead Sensors (Pix & SCT)

99.16% 60.85% 89.58%

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The MultiLepton Menu (III)

Check of the misalignment effect on

the track-match variables

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Misalignment : overview of the study

• First look at the 2012 data with 17.2 reco (m1xxx tag)runs : 200987, 201191, 200842, 200982, 200913, 201052, 200965, 201006, 200804, 200863, 200967, 201138, 201190, 200926, 201113, 201120

• Comparison with MC « à la » 17.2 : mc11_7TeV106046.PythiaZee_no_filter.merge.NTUP_EGAMMA.e815_s1272_s1274_r3395_r3417_p948/

• « Tag & Probe » very basic (no grl, no pileup reweighting, I just want to look at the shapes) Tag is tight, with pt>20 GeV, eta in the acceptance, Probe, with pt>20 GeV has only the calo and track cuts We look at the trackmatch Δη, Δφres and Silicon hits. Cut around the Z peak (+/- 10 GeV)

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Misalignment : cross-checks pile-up and Z mass

More pile-up in the MC ! Good Zmass reconstruction with this quick tag & probe

Looks like we have mor background in the data tails.

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Misalignment : eta and pt comparison

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Misalignment : what are we sensitive to?

• All the effect of misalignment between the calo and the ID :• Sagging of the electrodes Δφ (need to separate

charges and quadrants to see it)• Pear shape all• Tilt all• Shift wrt (0,0,0) Δη

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Misalignment : Δφres check• Data--- MC

Q>0Q<0

-π/4<ϕ<π/4

5π/4<ϕ<7π/4

3π/4<ϕ<5π/4

π/4<ϕ<3π/4

Everything is normal wrt the misalignement and charge asymetry, tails do to background electrons 16

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BARREL eta>0

-π/4<ϕ<π/4

3π/4<ϕ<5π/4

π/4<ϕ<3π/4

-π/4<ϕ<π/4

5π/4<ϕ<7π/43π/4<ϕ<5π/4

π/4<ϕ<3π/4

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BARREL eta<0

-π/4<ϕ<π/4 π/4<ϕ<3π/4

3π/4<ϕ<5π/4

-π/4<ϕ<π/4

5π/4<ϕ<7π/43π/4<ϕ<5π/4

π/4<ϕ<3π/4

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End cap eta>0

-π/4<ϕ<π/4 π/4<ϕ<3π/4

3π/4<ϕ<5π/4

-π/4<ϕ<π/4

5π/4<ϕ<7π/43π/4<ϕ<5π/4

π/4<ϕ<3π/4

End cap eta<0

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-π/4<ϕ<π/4 π/4<ϕ<3π/4

3π/4<ϕ<5π/4

-π/4<ϕ<π/4

5π/4<ϕ<7π/43π/4<ϕ<5π/4

π/4<ϕ<3π/4

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Misalignment : Δη check

We cut bigger than 0.005 so it’s ok.

Not yet understood for 2012 data!

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Misalignements : conclusion

• Δφres is well discribed by the MC, we have a very good agreement, mainly in the Barrel . • The effects that we can see are too small to impact the Identification and create

asymetries.

• Δη has some discrepancies in the End Cap that need to be understood, but that are very small for what we are interested in, and we are not sensitive to them

• 2012 data electrons benefit from the new reconstruction that allows more silicon hits in the tracks

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Going on optimizing …

Adding a new electron category conversion

like??

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Motivations :• New menu for the electron ID dedicated to the H4l analysis.

• A cut on the Blayer hits is rejecting a lot of conversions : • Rej : 6 14

But costs a lot on efficiency (~2% /electron >5% loss in 4e final state)

• We know that the electron candidates from conversions have a Δφres shifted in the positive side.

• Try to select a new catagory of electron failing the Blayer cut and cutting tighter (than the std menu) on the positive side of Δφres

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Δφres for conversions

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Using B-layer information• Creation of a new electron category : • Electrons with no B-Layer hit• Cut at 92% signal on Δφres positive side (don’t touch

the negative side ) Multilepton Multilepton

+ Blayer cutMultilepton + new category

Efficiency for Zee electrons

89.97% 88.13% 89.71%

Conversion rejection

6.01 15.90 6.82

-0.3% instead of -2% for the e efficiency 0.7% loss / 5.2% in a 4e final state

+13.5% of rejection gain of 30% for 2 conversions

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Results : electron efficiency

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Results : conversion rejection

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Results : conversion rejection

• We can use Δφres in combinaison to the Blayer cut to disantangle conversions and electrons without any Blayer hit.

• We want to have the best efficiency for the Higgs research so we

cutted not to hard

• In the future, as we know it is feasible we can play on this cut to rejection the conversions more or less depending on the efficiency we want

• Multilepton macro in egammaAnalysisUtils-00-03-09

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Summary plots

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Efficiency : EtMultilepton Multilepton + new BL category

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Efficiency : etaMultilepton Multilepton + new BL category

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Efficiency : pile-upMultilepton Multilepton + new BL category

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Conversion rejection : EtMultilepton Multilepton + new BL category

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Conversion rejection : etaMultilepton Multilepton + new BL category

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Conversion rejection : pile-up

Multilepton Multilepton + new BL category

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Hadrons rejection : EtMultilepton Multilepton + new BL category

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Hadrons rejection : etaMultilepton Multilepton + new BL category

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Hadrons rejection : pile-upMultilepton Multilepton + new BL category

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CONCLUSION

• First cross checks for 2012 HSG2 analysis :

Improvement of 44% for the H4e analysis efficiency

Great thing done at the end