A first look to the jetMET resolution in the VBF process q m n q’ W V q tag Sara Bolognesi (TORINO) PRS/jetMET meeting 07/06/05

VBF: jet kinematic Transverse momentum 2 q tag: high h, high pT and far away one from each other 2 q from boson decay: central, quite high pT and close by DR = √Dh2 + Df2 Pseudorapidity

FAMOS_1_2_0 NO PILE-UP resolution without calibration ICA05 ConeCut =0.5 Iterative Cone Algo ConeSeedEtCut = 0.5 JetRecom = 1 MidPointConeRadius= 1 MPCA MidPoint Cone Algo JetInput = EcalPlusHcalTower MidPointConeSeedThreshold = 0.5 EcalPlusHcalTowerEt = 0.5 KtJet RParameter Algo KRPA RParameter = 1 KDCA KtJet DCut Algo DCut = 400 KtJetAngle = 2 KNJA KtJet NJet Algo NJet = 4 GeneratorInputNoMuAndNu Iterative Cone Algo (JetRecom=1, ConeCut=0.5) impact of the g+jet calibration ConeCut =0.5 Iterative Cone Algo ConeSeedEtCut = 1.0 with and without GammaJet calibration JetRecom = 4 or 1 JetInput = EcalPlusHcalTower EcalPlusHcalTowerEt = 0.5

Jet resolution without calibration We match generated partons with reconstructed jets (pT > 30 GeV): events with exactly 4 jets in the final state, each of them with DR<0.2, 0.5 or 1 with respect to a single parton (with “matching efficiency” we mean the fractio of these events) With “resolution” we mean: reconstructed value – generated value resolution (%) = generated value Sara Bolognesi (TORINO) PRS/jetMET meeting 07/06/05

pT resolution DR(q,j) <0.2 DR(q,j) < 0.2 DR(q,j) < 0.5 ICA05 MPCA KRPA KDCA KNJA 5.0% 3.7% 4.1% 5.5% 8.0% matching efficiency ICA05 DR(q,j) < 0.2 5.0% DR(q,j) < 0.5 8.9% DR(q,j) < 1.0 11.3%

Resolution V->jj DR(q,j)<0.2 jets from V more problematic: ICA05 - not very high pt - we need to be precise to reconstruct mV and mH ICA05 matching efficiency DR(q,j)<0.2 MC jets 9.5% E+HTower 5.0% only events with DR(q,q) >1 considered MC jets 8.8% se ho tempo solo se DRjj>1 + se DRjj<1 provo a reco V con 1 jet solo E+HTower 3.5% - parton-jet matching efficiency problem !!! already at MC particle level !!! - pt and M(V) resolution problem -> calibration not sufficient !!! - asimmetry in M(V->jj) resolution not uderstood

The impact of the calibration g+jet calibration from CMS NOTE AN2005/004 (only available in FAMOS_1_2_0 for ICA05, Et reco scheme) Sara Bolognesi (TORINO) PRS/jetMET meeting 07/06/05

g+jet calibration DR(q,j)<0.2 ICA05 matching efficiency without calib. 5.0% with calib. 9.0% - matching efficiency not sufficient - FWHM increases with calibration - peak at 0.1 for pt resolution after the calibration (0.2 for M(V->jj) resolution)

M(W->jj) The best that we can do up to now: ICA05 with calibration (DR(q,j)<0.2) FWHM 30 GeV peak 94 GeV using E recom.scheme: FWHM 25 GeV peak 88 GeV FAMOS_1_2_0 doesn’t have the latest pion response tuning but it uses the latest ORCA GammaJet calibration CAVEAT: ... so, from this “incoherence”, some bias is possible But similar distributions have been found in ORCA (see R.Chierici talk (03/14/05) at PRS Session of CMS Week -> following plots)

ORCA-FAMOS (1) FAMOS ORCA Resolution on jet energy for jets from boson decay in top channel (ORCA) and in VBF process (FAMOS): in this case resolution = (Erec-Egen)/Erec RMS = 0.29 FWHM = 0.35 (Erec – Egen)/Erec peak ~ 0 mean = 0.09 FAMOS ORCA ICA05 calibrated jets E recom. scheme RMS = 0.29 FWHM = 0.35 peak ~ 0.05 mean = 0.06

ORCA-FAMOS (2) ORCA FAMOS W->jj mass in top channel (ORCA) and in VBF process (FAMOS): uncalibrated jets calibrated jets uncalibrated jets nopu calibrated jets nopu ORCA FAMOS ICA05 calibrated jets E recom. scheme FAMOS: FWHM = 25 GeV ORCA: FWHM = 25 GeV peak = 88 GeV peak = 90 GeV

MET resolution We try to reconstruct MET with different algorithms: FamosMETfromCaloTower Tower Correction = true TowerEtCut = 0.5 JetCorrection = true FamosMETfromJet JetUnclusterTower = true JetUnclusterCorrection = true The resolution is computed with respect to FamosMETfromParticle Sara Bolognesi (TORINO) PRS/jetMET meeting 07/06/05

MET resol. in VBF FWHM peak from Jets 0.63 -0.1 - we get a bias in the peaks toward low MET (overcorrected?) from Tower 0.60 -0.2 - too large FWHM: how can we improve the resolution?

Conclusions FINALLY SOME QUESTIONS AND WISHES FOR THE FUTURE: some problems BEFORE the calibration: M(V) resolution of ~30% parton-jet matching efficiency of ~5% (10% for MC jets) some problems AFTER the calibration: M(V) distribution with FWHM ~25 GeV and peak at ~90 GeV parton-jet matching efficiency of ~10% The resolution we get at the moment is not satisfactory ... but this is not the end of the history ... the work on the jet reconstruction and calibration is on-going so there is a big space for new improvements (am I right?) FINALLY SOME QUESTIONS AND WISHES FOR THE FUTURE: Sara Bolognesi (TORINO) PRS/jetMET meeting 07/06/05

Some questions ... Are the MC corrections something that we REALLY want to use in our analysis? Or they are simply a way to better understand our detector? If we want to use MC corrections, do we need to have “private” calibration in each analysis? (that is not so likely...) - we shouldn’t calibrate jet on our signal (otherwise a big bias!!!) - but can we use, all of us, the same calibration? For example can I calibrate my EW jets using MC correction developed for QCD jets ?? can be treated at the same way the gluon-QCD jets and the quark-EW jets ?

... and some wishes! A clear, up-to-date single documentation on the jet software packages: - What EXACTLY are CaloRecHit, EcalPlusHcalTower...? (how many towers? what is a single hit in the calorimeter? ... ) - What is the relative weight of ECAL and HCAL tower? How to set it? - Some hints about when you have to use one or another jet algorithm or recombination scheme and why - How to use the jet calibration: what algorithms and what parameters each calibration needs? - What about JetPlusTrack and algorithm for jet-tracks and jet-signal vertex association? ... and much more ...!! A precise evaluation of what pt, eta, invariant mass jet resolution we expect from CMS at the end of the history Please: when a new ORCA algorithm is developed, carry it immediately in FAMOS (the biggest part of the analysis are being shifted from ORCA to FAMOS)

~ 100% of the physics analysis needs to reconstruct jet and/or MET WE NEED YOUR KNOW - HOW !!! please use mailing list to comunicate any new algorithm, calibration, improvement etc... don’t hesitate to put A LOT of comment lines in the software examples ...Thanks for the attention...