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Summary: Jet/MissingEt (mon 9 th Jul)

Summary: Jet/MissingEt (mon 9 th Jul). Jet Reconstruction Basics (Iacapo Vivarelli). The signals in the calorimeters (calibrated at the EM scale) are “pre-clusterized”: Calorimeter towers: O(5000) towers per event, no noise suppression.

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Summary: Jet/MissingEt (mon 9 th Jul)

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  1. Summary: Jet/MissingEt(mon 9th Jul)

  2. Jet Reconstruction Basics(Iacapo Vivarelli) • The signals in the calorimeters (calibrated at the EM scale) are “pre-clusterized”: • Calorimeter towers: O(5000) towers per event, no noise suppression. • Topological clusters: O(100) clusters per event, noise treated, tries to resolve single particles. • Jet Algorithms (Kt, Iter. cone) run over topo/tower CLUSTERS. • Jets calibrated to EM scale. • Calo jet response non linear: different response to EM/Had shower components • Local Hadron calibration aims to overcome this. • H1 global weighting strategy in place: • Performance tested in a variety of different geometries, physics channels, jet fragmentation, showering model, CTB data. • Each of the above introduces uncertainties of the order of few percent (rarely larger than 5%). • Documented in the J6 CSC note. • Weights may be recomputed for latest simulation version, last done at V12. (F.Paige)

  3. AOD Content proposal(Peter Loch) • Only Cone 0.4 & 0.7. • made from Cells, (ESD only). • Maybe TruthCone0.4 & 0.7. • Full truth now in AOD    (v14??...not clear) • In V14, “H1-calibrated” or “Uncalibrated” are available from same object (1 collection). • NEW: “Towers from Clusters”: (not sure I really understand!) • Not same as old-style TowerJets: Clusters mean noise suppression. • Allows Tower Jet reconstruction from AOD. • Kt would be made on-the-fly from AOD. • In principle, better jets but Kt harder to calibrate at start-up. • Cone picks up small signals, sensitive to noise. • No cell signal weighting based calibration (?) • Can bias jet-finding by removing identified particles before jet-finding.

  4. Readiness of Jet and Missing Et Reconstruction for first data • Peter Loch ‘personal opinion’: 3 levels of jet calibration (B,S,L). • ‘B’ only uses data – no MC. • It is not ‘instead’ of others! • 3 samples, 3 tasks… • 1st: MinBias to do PileUp subtraction using jet area. • 2nd: relative calib. Using dijets • 3rd: abs. calib. using g/Jet. • Proposes ‘Jet Calibration Coordinator’ to help people. • Could be contacted for on-the-fly Jet Collections (?) • At some level, each physics analysis needs to ‘fine-tune’.. with help from coordinator!

  5. MissingEt(P. Loch, D. Cavalli) • EtMiss CSC note: https://twiki.cern.ch/twiki/bin/view/Atlas/EtMissCSCNote • Two Algorithms in production in Athena • MissingET (Cell-based, Milano, P. Loch) • ObMET (Object-based, Wisconsin) • Work in progress to merge these. • Move to full recalculation in the AOD • Not in 14.2.0, but coming soon. • Understand loss of precision wrt ESD calc. • Using various signals..on ttbar: • Kinematic fit of events after selection using all mass constraints in tt events (MWlep,MWhad,Mtoplep,Mtophad) • No b-tagging used. • The c2 of the kinematic fit can be used to suppress events with large Fake EtMiss. It is possible to classify events with a good EtMiss measurement useful to locate detector problems in first data • Background suppressed by c2cut DpT of the two reconstructed top very sensitive to EtMiss scale (2% no systematics)

  6. EtMiss trigger(D. Casadei) • New EDM for HLT [see twiki::AtlasHltMetSlice] • Basic information (global quantities) in TrigMissingET: • the 3 components (Ex, Ey, Ez) of the missing ET vector • scalar sums SumE and SumET of the total & transv. energy • Auxiliary information in TrigMissingET: from all components • name, flag, Ex, Ey, Ez, SumE, SumET, c0, c1, Nch, sumOfSigns

  7. Summary: Higgs (thu 12th July am)

  8. Higgs WG Activity during data taking(A. Nisati) • Tight collaboration with CP working groups • Studies can be done with less than 1fb-1, results feeding back to improve analyses. • e,g reco: ok, but improve • g conversion recovery • Pile-up effects • Electrons: Higgs WG contributed to long. weights. Must check in data • Work with egamma on id-optimisation, track isolation in pile-up. • Muon reco: many colleagues active; • Contribute to eff. Tag/probe, mu system alignment • Tau reco: H->tt, MSSM H->tt, more participation by charged Higgs. • Jet/MET: VERY important; many channels. ~100Gev • MET resolution v important esp. with pileup: • B-tagging: many analyses affected • ttH(Hbb), HWW,Charged H, MSSM Hmm, Htt, ttH(HWW). • Aim to contribute to b-tag eff. measurement. • Trigger: Need to check and plan to check: • Rates, efficiencies, biases introduced in Higgs Analyses! • ETMiss trigger: interest from charged Higgs. • Tau, already involved • Forwaed jets+MET and central jets, already involved. • e/m trigger: many groups involved • Suggesting “Topical” meetings for Z+jets (SM,Jet/Met,Higgs), g (SM,Higgs),ttbar(top,Higgs)

  9. “Summary of the summary” • Same slides on ‘new structure’: Tracking>>CP,Top/SM,Higgs/Exotics << MC • These meetings every ~6weeks, fitting as much with ATLAS meetings as possible. • Proposed dates: • 9. – 12. June (first meeting) • 7. – 11. July (ATLAS week at Bern, time for perf. & physics is limited) • 27. – 29. August (three days, remaining days of the week could be used • for other meetings, subdetectors, parallel meetings) • 06. – 10. Oct. (ATLAS week at CERN) • 01. – 05. Dec. (ATLAS week at CERN, T&P week style, no CB) • Selling Atlfast-II again… • New CAM (Common Analysis) Meetings to decide DPD contents • Common tools presented at CAM (tag jet, trk isol, tag& probe etc).

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