Transcript Summary: Jet/MissingEt (mon 9 Jul) th

Summary: Jet/MissingEt
th
(mon 9 Jul)
Jet Reconstruction Basics
(Iacapo Vivarelli)
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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.
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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.
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H1 global weighting strategy in place:
– Performance tested in a variety of different geometries, physics channels, jet
fragmentation, showering model, CTB data.
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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)
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.
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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.
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…
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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!
t0
L
S
B
time
“Local Hadronic”
1. PileUp correction
2. relative JES corrections
3. absolute JES corrections
“Sampling”
1. PileUp correction
2. absolute JES corrections
“Baseline”
1. PileUp correction
2. relative JES corrections
3. absolute JES corrections
local hadronic calibration
(highest MC quality requirements,
good understanding of calo
signals)
calorimeter sampling energy weighted calibration
(modest MC quality requirements, reasonable
understanding of calorimeter signals)
“data only” calibration
(no use of MC at all, reasonable understanding of calorimeter signals)
JES systematic error*
Relative energy resolution
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 c2 cut
DpT of the two reconstructed
top very sensitive to EtMiss
scale (2% no systematics)
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
Summary: Higgs
th
(thu 12 July am)
Higgs WG Activity during data taking
(A. Nisati)
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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
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Muon reco: many colleagues active;
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MET resolution v important esp. with pileup:
B-tagging: many analyses affected
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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
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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.
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:
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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)
“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:
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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).