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IPRD06 Siena, October 4, 2006 1/20 Martijn Mulders, CERN

Muon Reconstruction and Identificationin CMS

Martijn Mulders (CERN)

for the CMS collaboration

10th

Topical Seminar on Innovative Particle and Radiation DetectorsSiena, 1-5 October 2006

* Introduction

* Muons in CMS* Outside-in or Inside-Out* MC and beyond* Conclusion

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Introduction

Muons: clean signature

Efficient, precise, pure muon reconstructionover large momentum range indispensable forLHC physics program:

10% p/p for 1 TeV muon (Z'+-)

10-100s GeV (W, Z, H4)

even

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Compact Muon Solenoid

Huge 4 Tesla superconducting solenoid

Steel return yoke (2T), instrumentedwith Muon spectrometer

Tracker, ECAL, HCAL inside coil

} Large bending powerBdl

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4/22IPRD06 Siena, October 4, 2006 4/20 Martijn Mulders, CERN

The CMS muon system

See talks by G. Cerminara (DT) & J. Troconiz (barrel muon trigger)

250 Drift tube chambers (DT)precise tracking- 4 stations in muon barrel- 8-12 DT layers per station

Resistive Plate Chambers (RPC)fast response

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Muon StandAlone / Global tracking

Local reconstruction

Combine hits into segments (first seperately in 2Dprojections, then combine to full 3D segment with positionand direction)

Standalone muon reconstruction ( or level 2 in HLT trigger)

Segments from DT, CSC, hits from RPC--> Muon Seeds -->Find trajectories inside-out (Kalman Filter)

Backward Kalman filter to innermost muon station, followedby fit including vertex constraint

Global muon reconstruction (or level 3 in muon HLT trigger) Extrapolate back to tracker surface

Look for compatible track(s) in region of interest

Perform global track fit including hits from tracker and muon

system --> select final muon candidate(s) based on 2

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Standalone/Global muon reconstruction

Goal of 10% p/p for 1 TeV muon achievable

Using silicon tracker improves resolution by factor 10 at low pT !

Multiple scatteringdominates p < 200 GeV/c

Spatial resolution

& alignment crucial

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Standalone/Global muon reconstruction

Combination with silicon tracker also provides good chargeidentification at p ~ 1 TeV:

Global MuonStandalone Muon

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Performance vs rapidity

a) b)

c) d)

a) efficiency

stand-alone muon

b) efficiencyglobal muon

c) resolutionstand-alone muon

d) resolutionglobal muon

Difficult region

on boundarybetween muonwheels

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Two approaches

Standard approach: Outside-in

Standalone Muon

Combine with tracker track to fitGlobalMuon

Muon-ID: complementary Inside-out approach

Extrapolate every track outward

Find compatible deposits in

ECAL, HCAL, HO, muon hits Determine muon 'compatibility'

Plot with barrelboundary inefficiencydip

Recover inefficiencies at muon chamberboundaries and low pT (e.g. Muons

which only reach the first muon station)

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CMS detector slice

STARTfromTracker

ECAL HCAL HO(barrel only) Muon system

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Muon ID: separation

Example: pT = 10 GeV/c in CMS barrel

Discrimination between muons and pions

CMS NOTE 2006/010CMS NOTE 2006/010

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Muon 'compatibility'

Define muon compatibility based on energy deposits incalorimeter only (left), hits in muon system (right)

Clear separation between muons and pions possible

Choose requirement on muon compatibility based on analysis

(trade-off between efficiency and fake rate), e.g. >0.8 and >0.4

CMS NOTE 2006/010 CMS NOTE 2006/010

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Combined performance

Gain 10-15% efficiency in additionto global muon reconstruction

Small increase in fake rate (0.170.20% for pions in b quark jets)

To be optimised further

Promising for soft lepton b-tagging

CMS NOTE 2006/010

single muons, pT=5 GeV/c

In b quark jet, pT>5 GeV/c

6% gain wrt (global ORstandalone reconstruction)

In b quark jet, pT>5 GeV/c

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MC and Beyond

Muon reconstruction and identification performance

reported in detail in Physics TDR:

Volume I (CERN/LHCC 2006/001)

Volume II (CERN/LHCC 2006/021)

New data model and software framework CMSSW

Basic algorithms have been ported

Coming months: validate & recover performancesreported in physics TDR

CMSSW ready for some 'real' tests:

CSA'06 : large scale test of CMS computingincluding simulation, data transfer, reconstruction

CMS Magnet Test and Cosmic Challenge

See talk by D. Onoprienko

See talk by N. de Filippis

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Magnet Test & Cosmic Challenge

MTCC phase I (Aug 2006):

The magnet works!

Integrated full slice (~ few %) ofCMS detector

Millions of events, up to 4T field

Excercised new CMSSW software,data taking, transport

worked fine (not without challenges!)

See talk by D. Lazic

MTCC phase II (9-31 Oct 2006):

Precise field map (10-4)

Take data with HCAL, CSC, DT and RPC

Perform more of the reconstruction faster; 'online' on the trigger farmor in Data Quality Monitoring in the control room

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Reconstructing MTCC muons

Online event display wasrunning in the control room

Hits, segments :

* live * during run

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DT, RPC, CSC local reconstruction

CSC : Fast offline analysis (hits,segments) with excellent feedback

to both online & offline experts

Further offline analysis: matchbetween DT and RPC hits

Black = DT hits

Green = RPC hits

DT global (4 stations) and Barrel RPC local data (6layers) merged offline

Hits

Preliminary

A few hours days after

data taking in phase I...

* live * in phase II ?

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Standalone muon

Hits in the trackermodules, in ECALand HCAL, tracksegments in theMuon system

Standalone muontrack fit working

Extrapolation inmagnetic field totracker works !

Standalone Muon

Reconstruction

Extrapolation

to tracker

Preliminaryfew days after data taking

MTCC phase II: perform unpacking, localand standalone reconstruction 'online'

In online event display, fast offlinereconstruction, in Data Quality

Monitoring, perhaps on Filter Farm

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Global fit including tracker

Global fit of muon traversing

CSC, DT and tracker

Preliminary

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Conclusions & Outlook

Efficient, pure and precise identification and reconstruction of muons Standard reconstruction and inside-out muon identification

Performance reported in CMS Physics TDR Vol I & II

New data model and software framework

Basic algorithms have been ported

Ready for further refinement and validation

Millions of real muons recorded during CMS Cosmic Challenge

Succesful integration of CMS detector slice and functionality ofnew software framework demonstrated

Invaluable data set: test algorithms and compare Monte Carlowith actual detector performance

Focus on commissioning rest of CMS detector and software

... and looking forward to the real startup of LHC !!

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Fast offline 'analysis'

Run 2602, Aug 28, run with more than 1 million eventsEvery FED has data in exactly 1,000,502 events

Bunchcrossing

number

DTdata

size

FED number FED number

FED number FED number FED number

Raw data all events:

minutes hours delay

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Tracks & standalone muons

Reconstructed track in the tracker

3.5 T

Preliminary

run 2621, event 73459

Stand-alonemuon trackwith 3 CSC

segments3.8 T

few days after

data taking

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