Z ee, + jets gives a large statistics sample for the calibration of jets all the way to the forward region –Signal extraction does not depend directly on jet energy scale. Enough to have 5% (10%) energy scale uncertainty for central (forward) jets Study central jet veto with same sample Rate of leading jet in Z ee, + jets after central jet veto Jet Tagging and Jet Veto See W.Quayle’ s talk Mellado – Performance requirements
Technique Quite a few Taggers are available: –Impact Parameter based taggers (IP2D, IP3D) –Secondary vertex reconstruction based Provide discrimination based on a comparison between two hypotheses: –likelihood for a jet to originate from a b-quark (b) OR a light-quark/gluon (u) For each discriminating variable x in a tagger, build calibration functions for the two hypotheses – P b (x) and P u (x) The final discriminating variable (jet level) : W = x ln(P b (x) /P u (x)) Large W ~ high probability that the jet originates from a b quark Narain – b-tagging
Performance ( ) H events –Model u-jets using ttjj –release 10.0.1 –High eff crucial: ε b 4 SV1+IP3D IP3D IP2D Lifetime2D lhSig R u (ε b =50%)R u (ε b =60%) IP2D192 ± 261 ± 1 SV1+IP3D610 ± 12229 ± 3 as a function of p T and | | @ 60% efficiency J.-B. de Vivie, V.Kostyukhin A. Rozanov, L Vacavant
Planned Improvements goal to reach ε b =70 % with R u =100 A few planned improvements: (Some are already in 11.X.0 or will be in release 12) –combine space and soft leptons in jets –K 0 and Λ 0 impact parameters, no direct tracks IP –New tracking –track quality classification –multiple secondary vertices –shared/ambiguous hits, kill interactions –+…
Software Changes Transition from JetTag (‘previous’) and ParticleJet (‘new’) –A single collection for jets (calo+btagging information) –In the 11.X.0 branch Implies that ‘previous’ AOD not readable w/ ‘new’ release. For ‘previous’ btagging: –All releases 11.0.X are OK –Recommended: 11.0.4(,1,2) For ‘new’ btagging: –11.4.0 not recommended –11.5.0: Will be useable for b-tagging, including soft lepton taggers –12.0.0: scheduled for 1 st half of May… –possible to run ‘new’ btagging in 11.0.4(1,2) L Vacavant
Beam xing angle Half-angle 143 rad – vertical (CMS same angle, horizontal) ~ 1 GeV
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