Jets

1
Jets Missing ET

• G. DissertoriN. Varelas

• Both for Jets and MET
• Present status
• ongoing validation activities
• Plans for the near term - work to be done
• Group structure
• News
• Summary

CMS Italia, Napoli Feb 13, 2007
2
Detector -gt Jets MET
Calibration constants used up to this point are
a responsibility of DPG
ECAL Calibration to p response
DPG
JetMET Group
Note to be also considered in the future
Different input to Jet Reco and MET Reco, such
as Particle Flow Objects, charged tracks,
3
JETs
4
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 scheme CMSSW E-scheme
5
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
  ?confId9316
• 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

6
JW Summary Jet Physics

• Physics Needs
• Lowest ET thresholds used in most areas 30 GeV
• Uncorrected 20 GeV

J.dHondt (13.12.06)
7
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) D1
• apparently not optimalstudy of smaller
  values requested (ATLAS D0.6)
• Current CMSSW implementationknown to be buggy
• About to be implementedas external package

8
JW 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

RelVal/2006/9/26/RelVal101BJets50-120/GEN-SIM-DIGI
-RECO/
A. Heister, D. Kcira, A. Oehler
9
JW 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 lets 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)
10
JW Summary Particle Flow

• 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

11
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

12
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 calibrated by
  taking into account the e/h response in ECAL
  HCAL
• With additional corrections for non-linear
  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
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)

14
JW Summary Calibration/JES (4)
A.Bhatti (14.12.06)
A lot of space for many tomake
important contributions
15
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.
• Photonjet O. Kodolova (Moscow) et al.
• MET resolutions total event ET
• R. Cavanaugh, B. Scurlock (Florida)

16
PTDR(Vol.1) Validation Plots Jets (1)
P.Janot SDPV (20.12.06)
Fig.s 11.3/4/6/7/8/9 jet reco efficiency, energy
response, energy/angular resolution vs pT and ?
17
MCJet 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 lt
  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

18
Raw Icone5 Energy Response1_2_0 vs ORCA
ORCA
1_2_0

• Reasonable comparison in HB and HE
• A big difference in HF, understood due to problem
  in HF shower library

19
Corrected Icone5 Response vs h and ET

• Closure tests corrections work within a few ,
  except for low Gen ET lt 30 GeV (due to poor jet
  resolution at low ET)

20
Corrected Icone5 ET Resolutions1_2_0 vs ORCA
1_2_0
ORCA

• Corrected resolutions are similar between 1_2_0
  and ORCA problem in angular resolution
  understood by now

21
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

22
Plans Jet Algorithms (2)

• kT Algorithm
• Continue supporting standard kT algorithm with
  D1
• Study in detail FastJet (now external package in
  CMSSW)
• Support both D0.6 and D1
• 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

23
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)

24
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!

25
Missing ET
Energia mancante
26
PTDR Vol. 1 MET
n towers
R.Cavanaugh (2.11.06)

• Missing Transverse Energy
• Low luminosity Pileup included
• ltMETgt from QCD
• Stochastic term ? 123v?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
27
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 Roeck
28
MET 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
  ?confId6002
• A long ToDo list

29
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

30
Fig. 11.10, min-bias w/out PU
QCD 0 lt pt-hat lt 15 w/out PU, Scheme-B thresholds
Min-bias w/out PU, 0.5 GeV Thresholds on HCAL
cells
ltSETgt22 GeV
ltSETgt190 GeV
CSA06
PTDRv1
PTDRv1
sX2 GeV
sX6 GeV
CSA06
31
Fig. 11.11, QCD 0 lt pt-hat lt 15 w/PU
QCD 0 lt pt-hat lt 15 w/out PU, Scheme-B thresholds
PTDRv1
QCD 0 lt pt-hat lt 15 w/PU, 0.5 GeV Thresholds on
HCAL cells
ltSETgt22 GeV
ltSETgt396 GeV
CSA06
PTDRv1
sX10 GeV
sX2 GeV
CSA06
32
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 _at_ L1/HLT
• Corrections/Calibration at the trigger level
• Thresholds, prescales, rates
• Plans for 900 GeV running

33
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, p/e, )
• Muon/electron/photon corrections
• Interesting/difficult very high-pt muons
• Residual corrections (min-bias, QCD di-jets,
  Z/Wjets, )
• Understand impact and handling of varying beam
  conditions
• Look at METperp, MET significance
• MET Commissioning for early physics

34
Plans for MET (3)

• NoteWe 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!

35
Group Structure
Missing ET
Jet Energy Scale
Jet Algorithms
Group Representatives
Simulation/MC Production Tulika Bose
Onl Selection Lenny Apanasevich
HCAL DPG Olga Kodolova Michal Szleper
Software Robert Harris (Jet) Fedor Ratnikov
(Jet) Bobby Scurlock (MET)
Physics Tools Attilio Santocchia
ECAL DPG TBA
Particle Flow/t Joanna Weng
36
News/Summary

• MC pass with CMSSW 1.2.0 getting close to
  completion
• QCD, gjet, Wjets w/ and w/o PU
• https//uimon.cern.ch/twiki/bin/view/CMS/HighLevel
  Trigger06ExerciseMCSamples
• 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

37
News

• We are working on a JetMET project plan for
  2007
• Identifying tasks
• and the related peoplepower
• If we havent 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
• Groups twiki page under construction

38
Summary

• 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 questaria importantissima
• Ce un bel mucchio da fare.
• Grazie per linvito

39
PTDR(Vol.1) Validation Plots Jets (2)
P.Janot SDPV (20.12.06)
Figures 11.21/22/24/25/27 calibration from
dijet, gamma-jet balancing
40
PTDR Validation Plots MET
P.Janot SDPV (20.12.06)
Figures 11.10 to 11.16 sum ET, Exmiss with/out
pileup, resolutions from Min-Bias, QCD samples