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
12MAR2009 Xvc - TIPP09
ECAL / HCAL time alignment
HCAL
ECAL
Within each detector the RMS of R is coherent with time aligned cells within 3 ns
12MAR2009 14Xvc - TIPP09
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
12MAR2009 Xvc - TIPP09 16
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%
12MAR2009 Xvc - TIPP09 18
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
12MAR2009 20Xvc - TIPP09
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
12MAR2009 Xvc - TIPP09 23
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
12MAR2009 27Xvc - TIPP09
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
12MAR2009 Xvc - TIPP09 33
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
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