Commissioning with cosmic rays of the Muon Spectrometer of the

ATLAS Experiment at LHC

Luca SpogliUniversità Roma Tre & INFN Roma Tre

LNF Frascati Spring School 2007

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Outline

The ATLAS experiment at LHC Muon Spectrometer Commisioning Status Test with cosmic rays Summary

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ATLAS detectorMuon Spectrometer

Electromagnetic Calorimeter

Solenoid

Forward Calorimeter

Endcap Toroid

Barrel Toroid

Inner DetectorHadronic Calorimeter

Radiation Shielding

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good space resolution (~100 μm per point) pt/pt 2-3% @ pt<200GeV/c

pt/pt 10% @ pt 1TeV/c

MDT (Monitored Drift Tubes)MDT (Monitored Drift Tubes)

Tubes per layer

Layer per multilayer

Chamber lenght (mm)

Chamber heigth (mm)

~~1200 chambers / 1200 chambers / ~7000 m~7000 m22

MDT RPC

TGC

CSC

ECT

=1=1.4

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MDT Calibration: r(t)

Drift time measurement Determination of space-time

relationship r(t) via autocalibration

Time measurement

rt-relation with a typical accuracy of 10µm

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Muon Reconstruction

MDT mutilayer

In a single multilayer

Track segments

Momentum measurement from sagitta determination p=0.3 Br

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Installation and commissioning

Installation in the pit started in Summer 2005

First tests with cosmic muons during Summer 2006

First curved muon (magnetic field on) in November 2006

MDT chamber installation completed in the barrel region

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Installation

It is not an easy task...It is not an easy task...

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Cosmics 19-20 November data Sector 13 with RPC timing

informations Magnetic field on-off ~1 Mevents 9 chambers Many tests on MDT’s

Drift behavior Calibration Efficiency Noise Dead channels Preliminary alignment

Some results in this talk Sector 13

Side A

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Event Display

BIL chamber

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Fired tubes per event

Accidental trigger coincidences

6 multilayers

4 multilayers

2 multilayers

Number of Fired Tubes / event

...after noise reduction cuts

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Impact of magnetic field on r(t)

B field parallel to the wire

Electrons do not travel straight forward radially

They travel under an angle ψ

Drift time t for a certain radius r increases

B field expected to change drift-to-B field expected to change drift-to-radius relationship by radius relationship by Lorentz angleLorentz angle

τ: mean time between collisions

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µ-µ+

Ratio of µ+ / µ- = 1.48±0.27

Measured muon spectra

Momentum (GeV)

According to P.D.G Charge ratio of cosmic ray muons is between 1.1 - 1.4 from 1 to 100 GeV Effects of geometrical acceptance have to be taken into account

Z coordinate

Big shaftSmall shaft

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Big shaft~18 m

Small shaft~12 m

SIDE A

SIDE C

Surface-Pit~100m

Sector 13Side A

Muons coming from the shafts, are deviated in the upper part of Muon Spectrometerbefore ending in sector 13; due to the magnetic field µ+, µ- result in different angles.

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Conclusions

Barrel installations is completed Test with cosmic muons: complete

analysis of sector 13 data Systematic study of the MDT

performance over the all barrel sectors (magnetic field off)

Further tests with cosmics in June with B field on.

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Backup slides...

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Energy per Proton 7 TeV

Bunch spacing 25 ns

Bunch size 15 m 12 cm

Protons per bunch 1011

Bunches per ring 2835

Beam mean life 10 hours

Project Luminosity 1034 cm-2 s-1

Circumference 27 Km

Collisions per bunch 25

Detection of Higgs decay final states:H ZZ 4µ “Golden Channel”

Higgs @ 114.1GeV < mH < 1 TeV

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two multilayers of 3 (in Middle and Outer two multilayers of 3 (in Middle and Outer rings) or 4 (in the Inner ring) layers of rings) or 4 (in the Inner ring) layers of staggered drift tubes each.staggered drift tubes each.

thin wall (400 μm thick) 3 cm diameter thin wall (400 μm thick) 3 cm diameter aluminum tubes.aluminum tubes.

low longitudinal diffusion gas mixture, low longitudinal diffusion gas mixture, 93%Ar−7%CO2, absolute pressure of 3 93%Ar−7%CO2, absolute pressure of 3 bar. bar.

Gold-plated W-Re anode wire, 50 μm Gold-plated W-Re anode wire, 50 μm diameter is tensioned at 350 g crimped in diameter is tensioned at 350 g crimped in copper pins.copper pins.

low gas gain of 2×10low gas gain of 2×1044 (3080 V andode (3080 V andode voltage) to avoid ageing effects.voltage) to avoid ageing effects.

good space resolution (~100 μm per point)

robust and reliable operation for many years (no ageing problems).

MDT (Monitored Drift Tubes)MDT (Monitored Drift Tubes)

From F.PetrucciFrom F.Petrucci

Tubes per layer

Layer per multilayer

Chamber lenght (mm)

Chamber heigth (mm)

~~1200 chambers / 1200 chambers / ~5500 ~5500 mm22

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Impact of resolutionImpact of resolution

Space resolution ~100 micron

Transverse momentum resolution

Z mass resolution

(combined with Inner Detector tracking)

Z->µµ

From TDR

Invariant Mass (GeV)

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ATLAS Installation Schedule 9.1

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Setup

13 Muon stations read-out

BIL

BML

BOL

BOFBOF

BIL 1BIL 3 BIL 2

BOF1BOF3

BML 3

BOL 3

Side A

From R. NikolaidouFrom R. Nikolaidou

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TDC vs ADC spectrum

Noise

Signal

AD

C c

ou

nts

TDC counts

Background

“double hits”

When a tube has a second hit in the same event.

From C.BiniFrom C.Bini

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Magnetic field map

Magnetic field strongly inhomogeneous, in particular in BILs!

From C.BiniFrom C.Bini

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Angle of tracks

µ-µ+

degrees

Angle of tracks with respect to vertical axis. Shift inspectrum for different signs (run with magnetic field on)

Muons coming from the small shaft

Big shaft

µ+ µ-

Angle of tracks: superposition of run with and without magnetic field

• µ- µ+ run with magnetic field on• µ run with no magnetic field

From R. NikolaidouFrom R. Nikolaidou