4/04/2001 Calorimeter shaking -Andrea Venturi - April '01 ALEPH week

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New ideas and old doubts about the calorimeter shaking procedure

Andrea VenturiINFN Pisa

4/04/2001 Calorimeter shaking -Andrea Venturi - April '01 ALEPH week

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Present status

• ECAL and HCAL cluster energies are changed according to the observed data vs MC discreapancies as a function of polar angle– qqbar events at Z peak

• polar angle from jet direction

– at a lower level w.r.t. EFLOW because of jet corrections

• PHCO for HCAL• PECO, PEST,ETDI,...for ECAL

– number of “raw” clusters is not changed

• it does not work if this is a relevant discreapancy

• Results (winter 01)– 4q: 9 MeV– electrons: 20 MeV– muons: 5 MeV– taus: 5 MeV

• The procedure has to be validate “a posteriori”– check “higher level” observables

before and after shaking: the changes should be of the level of the discrepancies

• angular bias• visible energy• ...

– understand the results• electron/muon difference: brems

corr ?

4/04/2001 Calorimeter shaking -Andrea Venturi - April '01 ALEPH week

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HCAL shaking

dataMC

data/MC

4/04/2001 Calorimeter shaking -Andrea Venturi - April '01 ALEPH week

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ECAL shaking

data/MC

dataMC

4/04/2001 Calorimeter shaking -Andrea Venturi - April '01 ALEPH week

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PHCO

Type 5(neut had)

Eflow

ETDI(towers)

PECO raw

PECOcorr.

Type 5(neut had)

Photons

Type 4(photons)

Eflow

Gampex

Corrections:leakageoverlapcracks

….

CoradocMC data

Platine

4/04/2001 Calorimeter shaking -Andrea Venturi - April '01 ALEPH week

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EFLOW energy: jet correction

dataMC

dataMC

4/04/2001 Calorimeter shaking -Andrea Venturi - April '01 ALEPH week

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Higher level observables and shaking

no shaking shaking

data MC (shaken)

black : MC (not shaken)blue : MC (shaken)

by Ann

4/04/2001 Calorimeter shaking -Andrea Venturi - April '01 ALEPH week

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ECAL is not easy

• ECAL is crucial and the present shaking is not that good:

• PECO raw vs PECO corrected– data vs MC discrepancies are

different– EFLOW (#5) uses PECO

corrected– EFLOW (#4) uses GAMPEX

• same correction as PECO corr. ?

– the shaking parameters are taken from PECO raw

– Why different discrepancies ?• it could be a useful tool to study

ECAL simulation discrepancies

– What should we use for the shaking ?

• should we use “shaking” ?

PECO corr: data/MC

PECO raw: data/MC

4/04/2001 Calorimeter shaking -Andrea Venturi - April '01 ALEPH week

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ECAL is not easy (II)

• Two different processes produce signal in ECAL

• e.m. interactions (photons, electrons)

• hadronic interactions (hadrons)

– data vs MC discrepancies can be very different

– Different shaking based on the particle id (identified photons/electrons) is not enough

• it does not take into account identification efficiency/purity

• it is not easy to propagate the shaking back to the “raw” banks

– cfr brems correction in lnqq

– Ideal: use of the MC history banks

• are they ok for ECAL ?

• Discrepancy is larger for type 4 and 5 separately than for the sum– shaking should “migrate” the

energy from photons to neutral hadrons and viceversa

• cfr. my test with modified ECAL noise banks

• study photon id algorithm to understand how to shake to change the algorithm performance

– shake each ECAL stack independently ?

• MC history banks ?

• Brems correction (enqq)– have specific studies ever been

done ?– check the effect of the shaking

4/04/2001 Calorimeter shaking -Andrea Venturi - April '01 ALEPH week

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std ENNO banknew ENNO bank

4/04/2001 Calorimeter shaking -Andrea Venturi - April '01 ALEPH week

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Photons: ad hoc corrections• Identified photon energies are

corrected with corrections (CORADOC) which are different between data and MC– how are they evaluated:

• pi0’s ?• di-muons radiative events ?• electrons ?• to be asked to MNM…(done!)

4/04/2001 Calorimeter shaking -Andrea Venturi - April '01 ALEPH week

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Photons (II)• Photons corrections are like jet

corrections:– they try to correct for the data

vs MC discrepancy– this has to be taken into account

in the shaking procedure• once the shaking has been

applied , new MC photon corrections have to be evaluated and used.

• not because photons are better !!

• But, are we sure about the present photon energy corrections:– do we need better correction or

tracking resolution problems ?

4/04/2001 Calorimeter shaking -Andrea Venturi - April '01 ALEPH week

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Summary

• To be understood– PECO: raw vs corrected– noise banks and better

agreement: why ?

• Not to be forgotten– photon energy corrections are

not taken into account in shaking

• neither if they are correct: less discrepancy

• nor if they are not correct: additional discrepancy

• To be done– shaking-dependent photon

corrections– check observables after shaking

• e/mu present difference

• To be checked– have photon corrections to be

improved ?– simulation of the electron brems

(reconstruction)• who knows if it was studied in

the early days ?