Download - Jets & Missing E T
Jets & Missing ET
G. DissertoriN. Varelas
CMS Italia, Napoli
Feb 13, 2007
Both for Jets and MET : Present status
ongoing validation activities Plans for the near term - work to be done Group structure News Summary
13.2.07
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet MET
Detector Jets & MET
ECAL Calibration to response
JetMET Group
Calibration constants used up to this pointare a responsibility of DPG
DPG
Note : to be also considered in the future : Different input to Jet Reco and MET Reco, such as Particle Flow Objects, charged tracks, …
Note : to be also considered in the future : Different input to Jet Reco and MET Reco, such as Particle Flow Objects, charged tracks, …
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JETs
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet MET
PTDR: Jets
Basic/Calo/Gen Jet Algorithms: Iterative Cone (IC) Mid Point Cone (MCone) Inclusive kT
Calo Inputs: Cells contribute to tower energy if they pass energy
thresholds
ORCA: ET recombination schemeCMSSW: E-scheme
NIC = Noise In Cone (GeV)JEL = Jet Energy Loss (GeV)
B scheme used by default in CMSSW JetMET Reco
An additional tower energy constrain of ET>0.5 GeV (E>1 GeV) is used in CMSSW Jet cone (kT) clustering
T scheme was used in most ORCA JetMET studies:
ET>0.5 GeV & E>0.8 GeV
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet MET
Status: Jets
Jet Workshop (JW): Dec. 13-14, 2006 Jet finding at all stages: Trigger - Reconstruction - Simulation Goal:
Get a complete picture regarding: the physics needs/issues with jets the jet algorithms currently implemented at all levels,
along with their performance the status/prospects of calorimeter/jet calibration
20 presentations Agenda: http://indico.cern.ch/conferenceDisplay.py?confId=9316
Sub-Sessions Physics with Jets (SM, BSM, HI), summary of TeV4LHC, TEVATRON/HERA experience,
Pflow, Jet Algos at CMS, Simulation/Generator, Calibration/Performance of Calorimeter, Triggering on Jets
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet MET
JW Summary: Jet Physics
Physics Needs: Lowest ET thresholds used in most areas: ~ 30 GeV
Uncorrected: ~20 GeV
J.d’Hondt (13.12.06)
13.2.07
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet MET
JW Summary: Jet Algorithms (1)
Implemented in CMSSW: Iterative Cone, Midpoint, kT
Run on generic collection of 4-momenta (candidates) kT algorithm:
Default (size parameter) D=1;
apparently not optimal;study of smaller values requested (ATLAS: D=0.6)
Current CMSSW implementationknown to be buggy
About to be implementedas external package D-parameter
kT
Les houches hep-ph/0604120
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet METJW Summary: Jet Algorithms (2)
Fast version of kT (FASTJET) : indeed very fast (à la Iterative Cone) Very interesting, of course also for Heavy Ion physics Question raised: implement it even at HLT level? FASTJET: new pile-up subtraction scheme proposed, to be
looked at
A. Heister, D. Kcira, A. Oehler
RelVal/2006/9/26/RelVal101BJets50-120/GEN-SIM-DIGI-RECO/
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet METJW Summary: Jet Algorithms (3)
CONE algorithms (“the devil lies in the details”): eg. Investigate issue of unclustered energy/dark towers as seen at the
TEVATRON
“2nd pass” option considered “Search Cone” option
(currently implemented and used in someORCA studies) NOT recommended by TeV4LHC
Algorithms in CMS and ATLAS: Is a “sharing” needed? First let’s understand if it is possible Recommendations from TEVATRON :
1) Use the same algorithms in the two experiments!2) Use both CONE and kT algorithms!
M. Zielinski (13.12.06)
13.2.07
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet MET
Different approach: use objects/particles identified
by particle flow algo and individually calibrated as input to jet algorithms
In principle should need much smaller jet correction factor
However, not as “straightforward” as the CaloTower approach
Close communication needed with HCAL/ECAL tower approach, understand the interplay/needs/impact
P.Janot (13.12.06)
JW Summary: Particle Flow
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet MET
JW Summary: Calibration/JES (1)
Tevatron experience / recommendation Understanding of JES needs TIME and MANPOWER:
start now to build a strong group (“dream team”) Have the tools ready “now”….
ECAL Software tools for calibration workflow and for mis-calibration
studies are in place Currently discussing on the final calibration strategy No detailed study yet on interplay between pure e.m. and
pion/jet calibration: to be done
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet MET
JW Summary: Calibration/JES (2)
HCAL DPG-calibration task: Produce all
constants needed to provide the energy in each tower
Example test beam result: Longitudinal Shower Profile for in HB prefers G4 LHEP over QGSP used at the moment…
Important task ahead: Pion response Pion response calibrated by taking into account the e/h calibrated by taking into account the e/h response in ECAL & HCALresponse in ECAL & HCAL
With additional corrections for non-linear With additional corrections for non-linear effects : effects : Hope to get an energy resolution in HCAL of ~ 80% for stochastic term & 8% for constant term using these methods
M.Velasco (14.12.06)
13.2.07
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet MET
JW Summary: Calibration/JES (3)
A complicated multi-step approach
Have to investigate a large set of different physics channels to obtain angular uniformity, relative and absolute energy scale
Example: di-jet balancing: Detailed study needed of systematic effects
Example: photon-jet: two calibration techniques investigated
At the moment also: MC-based corrections, tools in place and applied to large productions (for CSA06 and for 1.2.0, no PU yet) From D0
13.2.07
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet MET
JW Summary: Calibration/JES (4)
A lot of space for many tomake importantcontributions
A.Bhatti (14.12.06)
13.2.07
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet MET
Recent Validation Studies:
MCJet energy corrections R. Harris (Fermilab), S. Petrushanko (Moscow)
Jet response and resolutions J. Widawsky, M. Zielinski (Rochester)
Jet efficiencies L. Apanasevich (UIC) et al.
Jet corrections Dijet balance: A. Bhatti (Rockefeller) et al. Photon+jet: O. Kodolova (Moscow) et al.
MET resolutions & total event ET
R. Cavanaugh, B. Scurlock (Florida)
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet MET
PTDR(Vol.1) Validation Plots: Jets (1)
Fig.s 11.3/4/6/7/8/9: jet reco efficiency, energy response, energy/angular resolution vs pT and
P.Janot SDPV (20.12.06)
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet METMCJet Corrections
Corrections to particle level based on QCD Dijet Monte Carlo Methodology developed by Moscow group for
ORCA; ported to CMSSW, now LPC and Moscow groups working on it
Corrections available for Icone5 and Mcone5 in 1_2_0 & CSA06 Accurate within a few %, except for low Gen ET <
30 GeV At low ET, poor jet resolution makes large
corrections difficult
Response = CaloJet ET/GenJet ET Barrel: 1_2_0 within a few percent of ORCA Endcap: Miscalibration of HE in CSA06 data fixed
in 1_2_0 Forward: HF Shower Library in CMSSW different
than in ORCA
Barrel
Endcap
Forward
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet MET
Raw Icone5 Energy Response:1_2_0 vs ORCA
Reasonable comparison in HB and HE A big difference in HF, understood due to problem in HF shower library
1_2_0ORCA
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet MET
Corrected Icone5 Response vs and ET
Closure tests: corrections work within a few %, except for low Gen ET < 30 GeV (due to poor jet resolution at low ET)
13.2.07
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet MET
Corrected Icone5 ET Resolutions:1_2_0 vs ORCA
Corrected resolutions are similar between 1_2_0 and ORCA; problem in angular resolution understood by now
1_2_0 ORCA
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet MET
Plans: Jet Algorithms (1)
Validation/Performance Studies To be completed by end of this month
Develop a default Jet ID criteria
Re-examine default input thresholds for all algorithms Flexibility (different input configurations for each algorithm) vs. simplicity (a
common set of thresholds for all algorithms, even MET) Optimize reconstruction efficiency vs. fake rate Working together with the ECAL/HCAL DPGs
Iterative and Midpoint Cone Algorithms Re-examine default parameter space
overlap fraction cone area fraction (currently is set to =1) cone radius un-clustered energy – 2nd pass jets
13.2.07
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet MET
Plans: Jet Algorithms (2)
kT Algorithm Continue supporting standard kT algorithm with D=1 Study in detail FastJet (now external package in CMSSW)
Support both D=0.6 and D=1 Work with the physics groups towards an optimized default D-value
Studies of UE and PU energy subtraction scheme as proposed by Cacciari and Salam
Software Tools Attilio Santocchia is working on jet matching package
Detector - Particle - Parton Jets, Flavour assignment
Study jet triggering scenarios at HLT Some requests raised to consider even kT at the HLT
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet MET
Plans: Jet Algorithms (3)
Jets from other input collections Jets from tracks only
performance, resolution, corrections, adapted to which analyses, topologies?
Jets from Particle Flow objects (same questions as above)
Jets at the lowest ET range Very difficult area, but important in many analyses, eg. with jet vetos
Jet corrections Study impact of electromagnet. energy fraction of jets Impact/Contribution of ECAL to be studied in much more detail Develop flexible and data driven scheme (see also next slide)
which is also able to respond to quickly varying beam conditions (PU)
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet MET
Plans: Jet Energy Calibration Need to establish a data-driven calibration method for all jet algorithms
Rely on experience from Tevatron/HERA experiments Many tools in place from earlier studies …but there is much more to be done at all levels Establish release goals and review procedure
Long list of correction factors: Offset: Pile-up/noise/underlying event Calorimeter energy response Uniformity across eta, phi Showering effects Jet overlap effects Hadronization effects for correcting back to parton jets Heavy-flavor jets …
A lot of combinations: Most corrections depend on jet algorithm type, algorithm parameter set, CaloTower
vs Particle inputs, etc. Bottom line: Need to intensify and prioritize the effort now!
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Missing ET
Energia mancante…
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet MET
PTDR Vol. 1: MET
Missing Transverse Energy Low luminosity Pileup included <MET> from QCD
Stochastic term 123%√ET
1700 GeV ET 700 GeV PT dijets
50 GeV observed MET
MET Resolution Low MET :
approaches Jet size High MET :
approaches calo cell size
QCD
ORCA
n towers
∑∑ ++>=< TT
miss
TEEE 019.04.523.1 ∑∑ ++>=< TT
miss
TEEE 019.04.523.1
R.Cavanaugh(2.11.06)
13.2.07
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet MET
PTDR Vol. 2: MET Need
good communication analysis MET study group
Need to impose, perhaps to revisit the
JetMET recommendations for MET, systematics etc. (partially done for the PTDR)
Need to study MET corrections schemes
(not all used/tried so far) Need
to prepare for MET filter for real data, protect against detector and accelerator background
Need to get rid of too low MET cut analyses (some
sneaked into the PTDR) Need
a systematic comparison of FAMOS/ORCA/CMSSW
Energy flow techniques should help to improve the MET resolution
Albert de RoeckAlbert de Roeck
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet METMET Workshop
MET Days: Sep. 25-26, 2006 Organized by R. Cavanaugh and M. Spiropulu Focused on Commissioning Presentations on:
Tevatron experience Physics input Trigger Calibration ORCA validation studies DQM Commissioning CMSSW “first look” studies
Agenda: http://indico.cern.ch/conferenceDisplay.py?confId=6002
A long “ToDo” list…
NOT SUSY!
MET at DØ
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet MET
Ongoing MET validation studies
Not a lot of people working on it for the moment
Effort just started, here early results using CSA06 samples 1_2_0 samples with and w/o PU under investigation
Total event ET (SumET) and METx distributions METx resolution vs SumET
Both SumET and MET are global (calorimeter) variables Especially sensitive to differences in cell thresholds and pileup
conditions between ORCA and CMSSW samples
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet MET
PTDRv1
<ET>~190 GeV<ET>~22 GeV
X~6 GeV
Fig. 11.10, min-bias w/out PU
Min-bias w/out PU, 0.5 GeV Thresholds on HCAL cells
PTDRv1CSA06
QCD: 0 < pt-hat < 15 w/out PU, Scheme-B thresholds
X~2 GeV
CSA06
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet MET
<ET>~396 GeV
X~10 GeV
Fig. 11.11, QCD: 0 < pt-hat < 15 w/PU
<ET>~22 GeV
X~2 GeV
CSA06
CSA06
QCD: 0 < pt-hat < 15 w/out PU, Scheme-B thresholds
QCD: 0 < pt-hat < 15 w/PU, 0.5 GeV Thresholds on HCAL cells
PTDRv1
PTDRv1
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet MET
Plans: MET (1)
Validation of MET Low level (together with the HCAL/ECAL DPG):
Optimization of calorimeter energy thresholds Online/offline “cleanup filters” Detector and data quality monitoring
High level Comparison to ORCA (coordinated with the SDPV group) Physics performance
MET @ L1/HLT Corrections/Calibration at the trigger level Thresholds, prescales, rates… Plans for 900 GeV running
13.2.07
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet MET
Plans: MET (2)
Look at other approaches to MET Construct MET from recoil of high-pT objects
Using cone clustering Using kT clustering (should not leave any unclustered energy) Study for which analyses/topologies this might be advantageous
MET Calibration Type-1 from corrections to jets
A lot of knowledge gained in the jets area to be transported to MET Type-2 from corrections to CaloTowers (pile-up, UE, /e, …) Muon/electron/photon corrections
Interesting/difficult : very high-pt muons Residual corrections (min-bias, QCD di-jets, Z/W+jets, …) Understand impact and handling of varying beam conditions Look at METperp, MET significance
MET Commissioning for early physics
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet METPlans for MET (3)
Note:
We need help in ALL efforts of JetMET, in particular for MET !
Your contributions are most welcome here.
A challenging and important work to be done!
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet MET
Group Structure
JetMET GroupN. Varelas
G. Dissertori
Jet Energy Scale Missing ETJet Algorithms
Group Representatives
HCAL DPGOlga KodolovaMichal Szleper
Simulation/MC ProductionTulika Bose
SoftwareRobert Harris (Jet)
Fedor Ratnikov (Jet)Bobby Scurlock (MET)
Physics Tools
Attilio Santocchia
Onl SelectionLenny Apanasevich
Particle Flow/Joanna Weng
ECAL DPGTBA
13.2.07
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet MET
News/Summary
MC pass with CMSSW 1.2.0 getting close to completion QCD, +jet, W+jets: w/ and w/o PU https://uimon.cern.ch/twiki/bin/view/CMS/HighLevelTrigger06ExerciseMCSamples Will provide a reference sample for near term JetMET activities
Jet energy scale corrections for CSA06 and 1.2.0 (w/o PU) are available
Understanding of the Jet/MET performance is steadily improving in CMSSW
Group priorities for the next couple of months: Complete the Jet/MET validation coordinated by SDPV group Launch of the sub-groups and underlying activities JetMET Workshop in the Spring (probably mid April)
Focus will be on “Calibration Path for Jet/MET”
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet MET
News
We are working on a JetMET “project plan” for 2007 Identifying tasks …and the related peoplepower If we haven’t contacted you already in person, then please:
Indicate to us (email, phone) if you have interest in JetMET activities Your physics area of interest & tasks that you would like to work on
CMS Week (Feb 26 – March 2) There will be a JetMET session – please plan to attend
Bi-weekly group meetings will start on March 8 Note : tomorrow, 16h, we will have a JetMET meeting!
Subscribe to the CMS JetMET HyperNews list Group’s twiki page under construction
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G. Dissertori N. VarelasETH Zürich Univ. Illinois, Chicago
Jet METJet METSummary
At LHC almost all the time we will see Jets and MET! … and sometimes we will see leptons and photons…
CMS-Italia :siete “invitatissimi” a partecipare al lavoro in quest’aria importantissima
C’e’ un bel mucchio da fare….
Grazie per l’invito