Commissioning the LHCb calorimeters with cosmic rays

Commissioning the LHCb calorimeters

with cosmic rays

Xavier Vilasis-CardonaOn behalf of the

LHCb calorimeter group

12MAR2009 1Xvc - TIPP09

1st international conference on Technology and Instrumentation in Particle Physics TIPP09-Tsukuba, Japan, March 2009

Y~7mX~8.5m

Z~2.7m

HCAL

ECAL

PS/SPD

LHCb Calorimeters

12MAR2009 Xvc - TIPP09 2

10-250 mrad

10-300 mrad

VELOVertexing

MAGNET

Calorimeters

PID: e,, 0

Muon Stations

RICH 1 & 2PID: K vs.

π

Trackers TT+IT+OTMomentum resolution

• Preshower (PS)/Scintillator Pad Detector (SPD)

• Electromagnetic Calorimeter (ECAL)

• Hadronic Calorimeter (HCAL)See Andreas Schopper Talk

Commissioning Tools

• Noise measurements• Inject known patterns into system

memories• LED system

– ECAL, HCAL, PS, SPD• Cs source for HCAL • Time Alignement events -TAE events

– Store trigger + previous and next Bunch Crossing ID (Clock cycle identifier - BXID)

– Up to 15 samples – usually 5,

• Prev2, Prev1, T0, Next1, Next2

• COSMIC RAYS• Injection Test Events

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Full System Test (May 2007)

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Concrete WALL

ECS

LED systemCalibration Pulse

ECAL Crate

Storage

Control Room

DAQTFC

Cosmics at LHCb

• Vertical flow in cavern: – 0.9 Hz/m2 (under HCAL), <E>=50 GeV.

• PMT high voltages set initially to obtain an uniform gain on PMT of 2·105

• Trigger strategies

• First cosmics seen in December 2007• Overall more than 3M cosmic triggers

512MAR2009 Xvc - TIPP09

L0Decision

Unit

ECAL

HCAL

SPD mult.

Muon

AND OR

5-15 Hz

HCAL ECAL

PS SPD

Cosmic event in the 4 calorimeter detectorsExample of Cosmic Event in the Calorimeter

12MAR2009 6Xvc - TIPP09

Another cosmic event

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HCAL

ECAL

PS

SPD

HCAL ECA

LPSSPD

Cosmic Ray crossing the SPD

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• Check channel map identification along the DAQ and trigger path.

• Relative Time Alignment– Bunch Crossing ID (Clock cycle identifier)– Integration time

• Track reconstruction in the Calorimeter– PreShower and SPD Efficiency

• Provide Trigger for other subdetectors

Cosmics use

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Correct channel mapping with comics

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Missing signal due to mapping error in

software(may 2008)

Corrected

Trigger path validation with cosmics

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Wrong Trigger Cabling should

deliver this

Actually we had this

Detector time alignement (muon vs calo)

• Calo-triggered event

22/04/2008 Pascal Perret - LPC Clermont

Time slot Time slot

• Muon-triggered event: Muon signal seen 2 clock cycles earlier

12MAR2009 12Xvc - TIPP09 Time slotTime slot

Time Alignment Strategy

13

• Equalise an a-priori delay from theoretical values• Adjust BXID so that an event is mainly seen on Current• Adjust integration time t0

– Select the pair of BX with maximum signal• Prev1/Current vs. Current/Next1

– Compute the asymetry R

Nevt

iij

Nevt

iij

Nevt

iij

Nevt

iij

NextECurrentE

NextECurrentERj

)()(

)()(

tT0 Next1Prev1

25 ns

δTsamplingδTsamplingδTsampling

06.20149.0 dTR

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ECAL / HCAL time alignment

HCAL

ECAL

Within each detector the RMS of R is coherent with time aligned cells within 3 ns

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PS time alignment

• Integration time is the same for 1 PMT(64 channels)

PS aligned within 4ns

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Outer Middle

Inner

SPD time alignment

• SPD has binary output• Integration time is the same for groups of 64 channels• Asymetry is computed over the shape of the average ratio of

detected particles

Full SPD aligned within 5 ns

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Calorimeter Track Reconstruction

• A tool has been developped to reconstruct tracks in the calorimeter

• Determine azimuthal angle (φ) in HCAL & ECAL and combine them

• Select events with χ²<15• Selected tracks are extrapolated

for position & timing – PS/SPD – Other subdetectors

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PS & SPD Efficiencies

• PS – Efficiency 87 %

• SPD efficiency as a function of threshold– Threshold at 9σ above noise: ~500k

94%– Threshold at 0.5 MIP : ~1M 82 %– Threshold at 1.5 MIP : ~500k 19.6%

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PS calibration with cosmics

From Cosmics events : - Each PS region calibrated – using the time model of

signals

12MAR2009 19Xvc - TIPP09

Injection tests events

• SPD multiplicity was used as trigger for LHC synchronization tests• 1 injection test shot 3 h Cosmics• Coherent with cosmics results

Pascal Perret - LPC Clermont3/09/2008

Flow 0.1-1 MIP/cm2

SPD PS

Connectics problems

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Conclusions

• Calorimeter system has provided cosmic triggers to the LHCb detector

• Cosmics have allowed a first approximation to– Time alignment– Efficiency

• This procedures will be repeated with the first data

• And we are now of course

Eagerly waiting for collisions !12MAR2009 Xvc - TIPP09 21

Commissioning the LHCb calorimeters

with cosmic rays

Xavier Vilasis-CardonaOn behalf of the

LHCb calorimeter group

12MAR2009 22Xvc - TIPP09

1st international conference on Technology and Instrumentation in Particle Physics TIPP09-Tsukuba, Japan, March 2009

Backup Slides

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Photon – electron triggger path

• ECAL -> PS/SPD->TVB tested on cosmics

12MAR2009 24Xvc - TIPP09

Data Quality Survey

• Check of connections with cosmics– With 900 events, if all cables were not plugged or if backplane

connections were wrong, we would see (ie we checked that all cables are plugged at the correct place):

22/04/2008 Pascal Perret - LPC Clermont12MAR2009 25Xvc - TIPP09

# hits Prs #hits SPD #hits ECAL

#hits HCAL

ECAL HCAL

Bx

Bx x x

y y

# hits Prs #hits SPD #hits ECAL

#hits HCAL

ECAL HCAL

Bx

Bx x x

y y

Time alignement PS/SPD & ECAL/HCAL

12MAR2009 26Xvc - TIPP09

HCAL & ECAL: Time Alignment

Pascal Perret - LPC Clermont3/09/2008

Improvement in the internal time alignment of the ECAL with the HV corrections

Aout29776

RMS(RMS R)=0.076

RMS(RMS R)=0.039Aout: 87k Event

New Run 29 776PP

Forward tracks – PP:Slope = 2.38OffSet = -2.20 ns

ΔL

TH

CA

L -

TEC

AL

ECAL

HCAL

)()(

)()(

NextNCurrentN

NextNCurrentNR

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Front End Electronics

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Calorimeter Trigger System

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LHCb DAQ System

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Cosmics in the calorimeter

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Cosmics at LHCb

• Vertical flow in cavern: – 0.9 Hz/m2 (under HCAL), <E>=50 GeV.

• Horizontal muons: – <E>=100 GeV– <30º; 0.0046 Hz/m2 (outer HCAL x 40 m2 = 0.18 Hz)– <11º; 0.0009 Hz/m2 (inner HCAL x 15 m2 = 0.013 Hz )

3212MAR2009 Xvc - TIPP09

Time Alignment Strategy - SPD

• SPD has binary output• Integration time is the same for groups of 64 channels• Asymetry has to be computed performing statistics over

many events• Threshold value is capital

– Too low : noise– Too high : no signal

– Fixed at 9σ from the pedestal

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t0 (ns) t0 (ns) t0 (ns)

25

25

ii

ii

NN

NN

25

25

ii

ii

NN

NN

100 GeV PGun muons (SPD inner cell), 1k events, B off Threshold ~ 0.5 MIP Threshold ~ 0.25 MIP

SPD threshold dependence

• Using Cosmics sample study the efficiency as a function of threshold.– 9 sigma recipe: ~500k - 94%– 0.5 MIP recipe: ~1M - 82 %– 1.5 MIP recipe: ~500k - 19.6%

Correspondance of 9 sigma recipe to computed MIP

• Correction needed for cosmics• Select cosmics in middle BX

12MAR2009 Xvc - TIPP09 34