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

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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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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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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

http://indico.cern.ch/conferenceDisplay.py?confId=9316

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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)

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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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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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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)

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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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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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Jet METJet MET


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)

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Jet METJet MET


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

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Jet METJet MET


A lot of space for many tomake importantcontributions

A.Bhatti (14.12.06)

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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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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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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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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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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)

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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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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

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Jet METJet MET


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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Jet METJet MET


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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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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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)

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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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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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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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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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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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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

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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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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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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

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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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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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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

Documents

Jets & Missing E T