muon system and physics performance ludovico pontecorvo cern-infn

Muon System and Muon System and Physics PerformancePhysics Performance

Ludovico PontecorvoCERN-INFN

Fermilab 1/5/03 Ludovico Pontecorvo – CERN/INFN

ATLAS MUON 2

OutlookOutlook

The ATLAS muon spectrometer The ATLAS muon spectrometer

Physics GoalsPhysics Goals Resolution and AcceptanceResolution and Acceptance Signals & BackgroundsSignals & Backgrounds

The Magnet systemsThe Magnet systems

The Trigger and Tracking concepts The Trigger and Tracking concepts

Experimental results from Test beamExperimental results from Test beam


ATLAS MUON 3

ATLAS LayoutATLAS Layout


ATLAS MUON 4

The ATLAS Muon SpectrometerThe ATLAS Muon Spectrometer

Acceptance : Acceptance : ||| < | < 2.72.7Pt Resolution: Pt Resolution:

~~10% @ 1 10% @ 1 TeV/TeV/cc

< 3 % P< 3 % Ptt<250 <250 GeV/GeV/cc

End cap: 1 < || < 2.7Tracking with MDTs & CSCs Triggering with TGCs

Barrel: || < 1.0Tracking with MDTs Triggering with RPCs


ATLAS MUON 5

S.M. Higgs search S.M. Higgs search

Muons relevant for Muons relevant for Trigger and ID in the Trigger and ID in the

full energy rangefull energy range

MH= 130 GeVmuon spectrometer standalone

Standalone Standalone

measurementmeasurement

better than Inner better than Inner

Detector forDetector for

MMHH>180 GeV>180 GeV


ATLAS MUON 6

MSSM Higgs Bosons MSSM Higgs Bosons searchsearch

mmhh < 135 GeV < 135 GeV mmAA m mH H mmHH at large mat large mAA

A, H, H cross-section ~ tg2Best sensitivity from A/H , H

bbA/H :-- covers good part of region not excluded by LEP-- experimentally easier than A/H -- crucial detector : Muon Spectrometer (high-pT muons from narrow resonance)Relevant for mass and couplings measurement

5 discovery curvesm~11 GeV

A/H , tg = 38 A/H , tg = 38


ATLAS MUON 7

CSC

MDT+RPC

MDT+TGC

Signals and Signals and BackgroundsBackgrounds

Expected bkg rateExpected bkg rateExpected bkg rateExpected bkg rate

Single counting rate: Single counting rate: Barrel Barrel < 40 Hz/cm< 40 Hz/cm22

End Cap End Cap 20-1000 Hz/cm20-1000 Hz/cm22

Low Pt trigger

High Pt trigger

Photons and Neutrons are the Photons and Neutrons are the main main source of uncorrelated source of uncorrelated backgroundbackground Muon ratesMuon ratesMuon ratesMuon rates


ATLAS MUON 8

ResolutionResolution

Resolution limited by :Resolution limited by : M.S. and Energy Loss Fluct. @ 3% M.S. and Energy Loss Fluct. @ 3%

for 10 < Pt < 250 GeV/for 10 < Pt < 250 GeV/cc Chamber Resolution and Chamber Resolution and AlignmentAlignment

for Pt > 250 GeV/for Pt > 250 GeV/cc

Energy loss fluctuations

Multiple scattering

Chamber resol and align.

Muon spectrom. standalone

Inner trackerstand alone

The muon spectrometer resolution The muon spectrometer resolution dominates for Pt > 100 GeV/dominates for Pt > 100 GeV/cc


ATLAS MUON 9

The Magnet systemsThe Magnet systems

BT Parameters :

25.3 m length

20.1 m outer diameter

8 coils

1.08 GJ stored energy

370 tons cold mass

830 tons weight

4 T on superconductor

56 km Al/NbTi/Cu conductor

20.5 kA nominal current

4.7 K working point

8 separate coils


ATLAS MUON 10

Barrel toroid statusBarrel toroid status

The completion of these The completion of these components is expected by May components is expected by May

20032003

Conductor Conductor double double Pancake: Pancake: 14 out of 16 14 out of 16 readyready

Cryostat Cryostat vacuum vessel:vacuum vessel:5 out of 8 delivered5 out of 8 delivered


ATLAS MUON 11

End Cap ToroidsEnd Cap Toroids

Services Turret

Magnet Coils (4.5K)

Thermal Radiation Shield (80K)

Vacuum Vessel (300K)

Pancake Pancake windings: windings:

8 of 16 done8 of 16 done

Vacuum vessels Vacuum vessels delivered delivered at CERNat CERN


ATLAS MUON 12

Field MapsField Maps

Field Integral vs

X (cm)

Y (cm)

Need to measure accurately the coordinate inNeed to measure accurately the coordinate in

the non bending planethe non bending plane

RPC and TGCRPC and TGCField integral Field integral inhomogeneous inhomogeneous in the tracking in the tracking

volumevolume More than a single More than a single RT relation per wireRT relation per wire

Need to take into account the differences inNeed to take into account the differences in Lorentz angle for the calibration of theLorentz angle for the calibration of the precision chambersprecision chambers


ATLAS MUON 13

Trigger conceptTrigger concept

Trigger algorithm relies Trigger algorithm relies

on pointing coincidences on pointing coincidences

inin

two views of two (two views of two (low Ptlow Pt) )

or three (or three (high Pthigh Pt) units of) units of

trigger detectorstrigger detectors

Trigger detectors mustTrigger detectors must

have very good timing have very good timing

properties to allow bunchproperties to allow bunch

crossing IDcrossing ID

Low Pt trigger Thr @ Low Pt trigger Thr @ 6 GeV/c6 GeV/c

High Pt trigger Thr @ High Pt trigger Thr @ 20 GeV/c20 GeV/c

Trigger Coverage Trigger Coverage ||| < 2.4| < 2.4


ATLAS MUON 14

Trigger efficiency and Trigger efficiency and ratesrates

Muon trigger rate @ 10Muon trigger rate @ 1033 33 cmcm-2-2 s s-1-1 : : Low PtLow Pt (> 6 GeV/c) (> 6 GeV/c) 10 10 KHzKHz High PtHigh Pt (> 20 GeV/c) (> 20 GeV/c) 200 Hz200 Hz

Pt Gev/cPt Gev/c

Luminosity

Barrel

Tri

gg

er

rate

(H

z)

Tri

gg

er

rate

(H

z)102

103

104

Luminosity

Barrel

104

103Tri

gg

er

rate

(H

z)

Tri

gg

er

rate

(H

z)

Good safety margin over Good safety margin over accidental trigger rateaccidental trigger rate


ATLAS MUON 15

Barrel Trigger chambers: Barrel Trigger chambers: RPCRPC

Operating Conditions

(Egas~ 5 KV/mm)

Gas: C2H2F4 96.7% - C4H10 3% - SF6 0.3% ;

bakelite ~ 2x1010 cm ;

Gas Gap d = 2 mm ;

Graphite coated HV electrodes

Cu read out strips 30 mm pitchTime resolution ~1.5 ns

Bakelite Plates Foam

PET spacers

Graphite electrode

s

X readout stripsHV

Y readout strips

Grounded planes

Gas

Gas Gas Volume + Volume + spacersspacers

Read out Read out stripsstrips

Read-out electronicsRead-out electronics8 chs Ga-AS8 chs Ga-AS3 stage ampli.3 stage ampli.+discrim+discrim


ATLAS MUON 16

RPCs BML-D Tested in Naples since August 2002

0

20

40

60

80

100

120

140

Weeks

Un

its

Test rate: 8 chambers/week

Time

• Plateau efficiency• V-I curve• Noise• Muon radiography

Tests on Production Tests on Production chambers chambers

RPC Cosmic Test StationRPC Cosmic Test Station

RPC Muon Radiography:Innefficiency only close to spacer

positions


ATLAS MUON 17

RPC Ageing test RPC Ageing test

3 production RPCs currently ageing at 3 production RPCs currently ageing at the CERN Gamma Irradiation Facilitythe CERN Gamma Irradiation Facility

Aim to integrate 300 mC/cm2

10 Atlas Years with safety factor > 5 Measurement still ongoing Previous tests on RPC prototype showed good efficiency and time resolution after 8 ATLAS years

Ageing Progress

0

5

10

15

20

25

30

35

Date

tota

l cha

rge

(mC

/cm

^2)

Gap 1

Gap 2

Gap 3

Gap 4

Gap 5

Gap 6

2530

Tota

l ch

ar g

e (

mC

/cm

2) 15 mC/10 Days

time

Integrated chargeIntegrated charge


ATLAS MUON 18

END CAP Trigger Chambers: END CAP Trigger Chambers: TGCsTGCs

MWPC with small MWPC with small cathode-cathode cathode-cathode distance:distance:Anode pitch: 1.8 mmAnode pitch: 1.8 mmAnode-Cathode dist: 1.4 mmAnode-Cathode dist: 1.4 mmCathode-Cathode dist: 2.8 mmCathode-Cathode dist: 2.8 mm

Operating conditionsOperating conditionsGas Gas : 55 % CO: 55 % CO22 , 45 % N- , 45 % N-

PentanePentaneHVHV: 3.1 KV: 3.1 KVSaturated avalanche modeSaturated avalanche modeVery short drift time due to Very short drift time due to the thin gapthe thin gap ensures ensures the good time resolution the good time resolution needed for Bunch Crossing needed for Bunch Crossing IDIDWire signal used to provide the Wire signal used to provide the trigger, strip signals used for trigger, strip signals used for the second coordinatethe second coordinate


ATLAS MUON 19

Results from high rate Results from high rate testtest

Efficiency at ~ 1 kHz/cmEfficiency at ~ 1 kHz/cm22Efficiency at ~ 1 kHz/cmEfficiency at ~ 1 kHz/cm22

Efficiency with source offEfficiency with source offEfficiency with source offEfficiency with source off

25 ns

100 %

hit time distrib.hit time distrib. % hits in window

% hits in window

20 40 60 Time (ns)

20 40 60 Time (ns)


ATLAS MUON 20

Trigger Efficiency Trigger Efficiency under irradiationunder irradiation

(Wire only) Trigger Efficiency with source @2.8 kV

99.5

99.6

99.7

99.8

99.9

100.0

0 10 20 30 40 50 60 70 80

Time(h)

2 out of 3 3 out of 4 Global

~ 1 kHz/cm2


ATLAS MUON 21

Precision chambers: Precision chambers: CSCCSC

MWPC with symmetric cell where MWPC with symmetric cell where anode-cathode distance is equal to anode-cathode distance is equal to

the anode wire pitchthe anode wire pitch Anode pitch: 2.54 mmAnode pitch: 2.54 mmCathode read-out pitch: 5.08 mmCathode read-out pitch: 5.08 mmVery good spatial resolutionVery good spatial resolution: : 50 50 m per m per

planeplanereading charge on the cathode stripsreading charge on the cathode strips

Good time resolutionGood time resolution: : 7 ns7 nsDue to small drift time (30 ns)Due to small drift time (30 ns)

4 planes per chamber


ATLAS MUON 22

Results from high rate Results from high rate testtest

Inefficiency vs Rate

Inefficiency vs Rate

Inefficiency= distance from track > 300

m

Resolution vs Rate

Resolution vs Rate

The expected background rate The expected background rate at at =2.7 is 2.7 KHz/cm=2.7 is 2.7 KHz/cm22 (with safety factor 5)(with safety factor 5)

The CSC System can The CSC System can

provide very good space provide very good space

resolutionresolution

Distributions of Distributions of residualsresiduals::Reconstructed CSC track Reconstructed CSC track

position - Silicon Telescope position - Silicon Telescope extrapolationextrapolation

Tails mainly due to Tails mainly due to --

electrons electrons

at low rate, and to at low rate, and to

overlapping overlapping

signals at high rate.signals at high rate.

47 47 mm

Low Rate 0.1 KHz/cm2

Low Rate 0.1 KHz/cm2

69 69 mm

High Rate2.3 KHz/cm2

High Rate2.3 KHz/cm2


ATLAS MUON 23

Precision Chambers: Precision Chambers: MDTsMDTs

Drift tubes mechanical parameters:Drift tubes mechanical parameters:Tube Radius : 15 mmTube Radius : 15 mmTube thickness 400 Tube thickness 400 mmWire diameter. 50 Wire diameter. 50 mmTube length: 1-6 mtTube length: 1-6 mtChamber mech. Precision 20 Chamber mech. Precision 20 mm

Operating ConditionsOperating Conditions

Gas MixtureGas Mixture: 93 % Ar 7% CO: 93 % Ar 7% CO22

Absolute pressure: Absolute pressure: 3 Bar 3 Bar

HV:HV: 3080 V 3080 V

Gas Gain:Gas Gain: 2x10 2x104 4

Threshold:Threshold: 25 electrons 25 electrons

Reconstructed Reconstructed tracktrack


ATLAS MUON 24

ResolutionResolution

Muon Spectrometer Muon Spectrometer resolution @ High Pt resolution @ High Pt depends crucially on depends crucially on

Single station spaceresolution (6-8 meas.)

Low Rate 40-60 Low Rate 40-60

mm

High Rate 40-90 High Rate 40-90 mm

Radius mm

Space charge effect on the single tube resolutionSpace charge effect on the single tube resolution

Res o

l ut i

on (

mm

)

Single tube resolutionSingle tube resolution Precise knowledge of Precise knowledge of space-time calibration (RT-space-time calibration (RT-Rel)Rel) AlignmentAlignment

Space charge fluctuations at high irradiation worsen the resolution far away from the wire


ATLAS MUON 25

RT-RelationRT-Relation

Drift time (ns)Drift time (ns)

Tru

e R

T -

calib

rati

on

(m

)Tru

e R

T -

calib

rati

on

(m

)

The RT-relation close to the wire The RT-relation close to the wire is distorted by Threshold effectsis distorted by Threshold effects

-25 -25 mm

+25 +25 mm

RT relation known at the

level of 25 m over

almost all the drift distance


ATLAS MUON 26

Barrel AlignmentBarrel Alignment

The relative chamberThe relative chamber

positions should be positions should be

known with known with ~30~30 mm precision to ensure precision to ensure

high Pt resolutionhigh Pt resolution

alignment system alignment system

basedbased

on optical elementson optical elements

(RASNIK) to reconstruct(RASNIK) to reconstruct

and monitor the and monitor the

geometrygeometry

of the spectrometer of the spectrometer

withwith

the required accuracythe required accuracy

Projective Lines Projective Lines to monitor relative movements of stationsto monitor relative movements of stations Axial lines Axial lines to monitor chambers movement within a stationto monitor chambers movement within a station

Projective Projective lineslines

(RASNIK)(RASNIK)

Axial linesAxial lines(RASNIK)(RASNIK) Station 1

Station 2

Station 3


ATLAS MUON 27

Survey platforms

2 BML on rails

Projective platform

BML on rail BIL on

rail

2002: 2002: Barrel & End Cap System TestBarrel & End Cap System Test

Test the barrel and end-cap alignment conceptsTest the barrel and end-cap alignment concepts Test system and chamber performances with a barrel Test system and chamber performances with a barrel and end cap sector (6+6 chambers)and end cap sector (6+6 chambers)

Barrel Sector End Cap Sector

End Cap Stand

Barrel Stand

Magnet onVirtual IP


ATLAS MUON 28

Alignment test resultAlignment test result

Displace one chamber from middle station, along supporting Displace one chamber from middle station, along supporting railrail

Check alignment reconstructed position against Check alignment reconstructed position against

track reconstructed positiontrack reconstructed position

2.0

1.5

1.0

0.5

21.51.00.5

Dis

pla

cem

en

ts f

rom

tr

ack r

econ

str

ucti

on

(m

m)

Dis

pla

cem

en

ts f

rom

tr

ack r

econ

str

ucti

on

(m

m)

Displacement from alignment system (mm)Displacement from alignment system (mm)

The 15 The 15 m RMS of the residuals distribution proves m RMS of the residuals distribution proves the correctness of the alignment system conceptthe correctness of the alignment system concept

Residual difference between chamber Residual difference between chamber position using tracks and alignment position using tracks and alignment

systemsystem

B M L c o n t r o l l e d d i s p l a c e m e n t ( m i c r o n )

D e

l t a

Z

(

m i

cr o

n )

20

40

60

0

-20

-40

-60

0.5 1.51.0 2.0Position (mm)Position (mm)

Resid

uals

m

Resid

uals

m

RMS = 15 RMS = 15 mm


ATLAS MUON 29

ConclusionsConclusions

Construction and Tests:Construction and Tests:

What’s Next? What’s Next? System Test with Tracking and Trigger System Test with Tracking and Trigger chambers chambers Trigger System TestTrigger System Test

The The ATLAS Muon SpectrometerATLAS Muon Spectrometer will provide will provide powerfulpowerful muon trigger and identificationmuon trigger and identification over the full energy over the full energy range range with a large angular acceptancewith a large angular acceptance The The very good momentum resolutionvery good momentum resolution will ensure will ensure high qualityhigh quality stand alone measurement for most of the physics stand alone measurement for most of the physics channels channels under study (H->4under study (H->4, A->, A->, Z’->, Z’->

The The Magnet systemsMagnet systems are well advanced in the construction are well advanced in the construction

TriggerTrigger and and Precision chambersPrecision chambers are under construction are under construction

The chambers performance at The chambers performance at high ratehigh rate is adequate to the LHC environmentis adequate to the LHC environment The The alignment conceptalignment concept is validated by the results from is validated by the results from the 2002 System Test of a full sector of barrel and the 2002 System Test of a full sector of barrel and end-cap precision chambersend-cap precision chambers

muon system and physics performance ludovico pontecorvo cern-infn

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