4/04/2001Calorimeter shaking -Andrea Venturi - April '01 ALEPH week 1 New ideas and old doubts about the calorimeter shaking procedure Andrea Venturi INFN Pisa

4/04/2001Calorimeter shaking -Andrea Venturi - April '01 ALEPH week 2 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 ?

4/04/2001Calorimeter shaking -Andrea Venturi - April '01 ALEPH week 3 HCAL shaking data  MC data/MC

4/04/2001Calorimeter shaking -Andrea Venturi - April '01 ALEPH week 4 ECAL shaking data/MC data  MC

4/04/2001Calorimeter shaking -Andrea Venturi - April '01 ALEPH week 5 PHCO Type 5 (neut had) Eflow ETDI (towers) PECO raw PECO corr. Type 5 (neut had) Photons Type 4 (photons) Eflow Gampex Corrections: leakage overlap cracks …. Coradoc MC  data Platine

4/04/2001Calorimeter shaking -Andrea Venturi - April '01 ALEPH week 6 EFLOW energy: jet correction data  MC data  MC

4/04/2001Calorimeter shaking -Andrea Venturi - April '01 ALEPH week 7 Higher level observables and shaking no shaking  shaking data  MC (shaken) black : MC (not shaken) blue : MC (shaken) by Ann

4/04/2001Calorimeter shaking -Andrea Venturi - April '01 ALEPH week 8 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

4/04/2001Calorimeter shaking -Andrea Venturi - April '01 ALEPH week 9 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

4/04/2001Calorimeter shaking -Andrea Venturi - April '01 ALEPH week 10 std ENNO bank new ENNO bank

4/04/2001Calorimeter shaking -Andrea Venturi - April '01 ALEPH week 11 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!)

4/04/2001Calorimeter shaking -Andrea Venturi - April '01 ALEPH week 12 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 ?

4/04/2001Calorimeter shaking -Andrea Venturi - April '01 ALEPH week 13 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 ?