The BArreLMUON SYSTEM

Of cms

International Meeting on Fundamental Physics

El EscorialApril 5th 2006

Marcos Fernández GarcíaUniversidad Autónoma de Madrid

CMS at a glance

ECAL: PbWO4 crystals, short 0 and fast response, but low light yieldIntrinsic gain photodetectors: Silicon APD barrel,VPT for EEElectrons: (E)/E~0.5-1% (E>20 GeV)

HCAL: Brass+plastic scint. tiles readout by WLS+CFHadronization leaks after magnet caught by scint Hadron Outer (barrel)HCAL Energy resolution: Pions (E)/E~20%@50 GeV, ~15%(E>100 GeV)

Solenoid: Superconductor 4T L=13 m, 5.9 mMagnetic Field returns throughiron yoke

Tracker@ -20ºCPixel: =10(20) µm r (z)Strip Tracker: µstrips Silicon TIB~20 µm,TOB~40 µm

Trigger:Approx. 20 ev/bx @ L=1034/cm2s   bx=40Mhz 109 ev/sL1 FPGAs,ASICs, 312 µs output rate 105 HzDecision photon,e,µ,jets > pT cutsHLT output 100 ev/sReduction info, farm CPUs

Muon System: key for trigger. 250 DTs, 540 CSCs, 912 RPCs in 12 sectorsModerate pT resolution (comp. tracker)

Barrel: <1.2, B< & uniform, R(µ) 1 Hz/cm2, R(n bkgd)=1-10 Hz/cm2

Endcaps: 0.9<<2.4, B upto 3.5T, R(µ) 200 Hz/cm2, R(n bkgd)<1kHz/cm2

RPC:t~1 ns, identification bx

Length: 21.6 mDiameter: 14.6 m

12500 TonsReady to close: 30th July 2007

CMS three years ago

CMS now: MUONS

YB+2

YB-0

YB-1

YE+1 CSCs

YE+1

YB+2

Forward HFCAL(cabled)

Assembled on surface at point 5 in LHC ring

CSCs all @ CERN(>80% cosmics comm.)

Barrel~50% installed

CMS now: Magnet + HCAL

Magnetouter case+SC

YB+0

Magnet closedCooled downCoil powered May

HCAL on itstransport structure

Completed, 1st lowered

HCAL slid insidemagnet bore

Transport structure(will be removed)

Muon measurement

1) In the Inner Tracker2) With the muon system3) Inner Tracker+ Muon System

Muons are measured at the tracker with higher resolution. Why using Muon Chambers anyway?

Easier to find muon in the chambers than in the tracker. Once found in the barrel, the track isextrapolated backwards

The L1 trigger (decision taken 128 bx after current event) can not wait for tracker reconstruction

Tracker will not be fully aligned at the beggining of the experiment. Muons measured onlyusing Muon System

Muons measured in 3 different ways(central muons with enough pT):

=0

=1.5

Muon chambersActually they are ionization gas detectors. They detect only muons, because these are the only (charged) particles reaching that far in CMS.

Why Ar/CO2 (85/15)%?Ar=monoatomic e– undergo only elastic scattering with low energy loss

Only Ar excited atoms emit photons which induce new avalanches discharges

CO2 quencher required. Absorbs photons

Time (ns)Avalanche Constant vd

Øwire =50 µmWire positioning error=100 µmCell spatial resolution=250 µm

5 electrostaticelements

Vstrip

Vwire

Vbeams

= 1800

= 3600=-1200

Muon chamber’s core: Drift cell

Drift Cell:Muon ionises the gasElectrodes shape the fieldConstant drift velocity (roughly 50 µ/ns)TDC µ crossing position known

Half cell staggering solves the left-right uncertainty

A superLayer is just 4 layers of

staggeredcells

3 SLs Muon Chamber

2

1

Honeycomb

Muon chambers

R 150 µm 200 µm Angle=1 mrad

RPC

Muon Chamber, cabled on cosmic calibration bench

Scintillator trigger panels

(not scaled)

Muon Chambers in Level 1 trigger systemOn-chamber Local Trigger Logic

1

1

2

• Muon L1 Trigger based on custom electronics

BTI: alignment in 4 layers, bx identificationTRACO: Combines segments from the SLs.TS: Selects best two segments/chamber

Track Finder: Connects segments of chambers in sectorAssigns pT, angle and quality

Local trigger (on-chamber):

Regional trigger (off-chamber)

Regional Trigger

Chamber certification at the ISR lab

Muon chamber storage and certification area at CERN uses the (dismantled) ISR facilityNote: ISR was the world’s first pp collider (1971-1984), 62 GeV cdm, record L @ hadron collider till 2004

As of March 2006, 117 chambers pending for installation (133 already certified and installed)

Currently 3 physicist, one engineer, 2-3 technicians devoted full time to this task

Chamber certification process takes approx. 2 months. With current buffer of chambers, we certify 2-3 chambers/week

After certification, chambers are installed at a rate of 2-4 chambers/day (depends on schedule)

After installation chambers are commissioned in the wheels, approx. 5 chambers/week

ReceptionCertification Installation Commissioning

Work acknowledged to all those pictured below, as well as casual collaborators from institutes

J. PuertaCERN J.M. Ahijado

CIEMAT

VincenzoINFN Bo

A. BenvenutiINFN Bo

S. Di VincezoCERNM. Chamizo

CIEMAT

+ Vittorio (INFN Bo), G. Fetchenhauer (Aa)(…)

Reception

Chamber dressing

SurveyUnload

Gas MFHV CablesPADC

ChamberCertification

@ ISRSTEP I

Storage

ChamberCertification

@ ISRSTEP II

Intervention

Curr

ents

time

CosmicsProblemidentification

2-3 interventions/chamber

Intervention

Insertion

Commissioning

From ISRto SX5

Insertion

Commissioning of 2 sectors simultaneouslyTrigger logical AND of all 4 chambers (across 2 sectors!)

…and actually, everything works

Perspectives

CMS installation progressing on a daily basisHeavy lowering [July 2006-March 2007]

…and Conclusions

2007 LHC related dates:

[Sept-Oct] Pilot RunFirst collisions: 1+1 bunches-43+43 bunchesL1027 1030 cm-2s-1

Up to 10 pb-1, enough for subdetector calibrations

[Nov-Dec] First PhysicsRuns at 75 ns (936 bunches) and 25 ns (2808)L~ 1032 cm-2s-1 (75ns,936b)…21033 (25ns,2808)

[Jan-Mar 08] ShutdownInstallation of staged detectors

[Apr 08-…] Expected 7 months run

The LHC time is already here

CMS close to completion. Final detectorsbeing installed:

Magnet and HCAL … doneRest follow the path (and the schedule)

Muon chambers key trigger detectorsand very important for high pT muons

Chambers certified prior to installation…and commissioned after installationSo many tests ensure a performant µ system

Packed schedule from now on:Magnet test/Cosmic ChallengeFinal installation (surface and pit)First collisions … and last holidays!

First endcap wheel lowering by October 2006Last DT chamber installed by Dec06-Jan07