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Commissioning LHCb Calorimeters with Cosmic Rays

Presentation on the commissioning process of LHCb calorimeters using cosmic rays at the TIPP09 conference. Topics covered include noise measurements, LED systems, trigger strategies, time alignment, track reconstruction, and efficiency calibration.

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Commissioning LHCb Calorimeters with Cosmic Rays

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  1. Commissioning the LHCb calorimeters with cosmic rays Xavier Vilasis-Cardona On behalf of the LHCb calorimeter group 1st international conference onTechnology and Instrumentation in Particle Physics TIPP09-Tsukuba, Japan, March 2009 Xvc - TIPP09

  2. LHCb Calorimeters RICH 1 & 2 PID: K vs. π • Preshower (PS)/Scintillator Pad Detector (SPD) • Electromagnetic Calorimeter (ECAL) • Hadronic Calorimeter (HCAL) See Andreas Schopper Talk 10-250 mrad 10-300 mrad MAGNET Y~7m X~8.5m PS/SPD HCAL ECAL Muon Stations Calorimeters PID: e,, 0 VELO Vertexing Trackers TT+IT+OT Momentum resolution Z~2.7m Xvc - TIPP09

  3. 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 Xvc - TIPP09

  4. Full System Test (May 2007) LED system Calibration Pulse ECAL Crate Storage Concrete WALL TFC DAQ ECS Control Room Xvc - TIPP09

  5. Cosmics at LHCb • Vertical flow in cavern: • 0.9 Hz/m2 (under HCAL), <E>=50 GeV. • PMT highvoltages set initiallytoobtainanuniformgainon PMT of 2·105 • Triggerstrategies • Firstcosmicsseen in December 2007 • Overall more than 3M cosmictriggers L0 Decision Unit ECAL AND OR HCAL 5-15 Hz SPD mult. Muon Xvc - TIPP09

  6. Example of Cosmic Event in the Calorimeter ECAL HCAL PS SPD Cosmic event in the 4 calorimeter detectors Xvc - TIPP09

  7. Another cosmic event HCAL HCAL ECAL PS ECAL SPD PS SPD Xvc - TIPP09

  8. Cosmic Ray crossing the SPD Xvc - TIPP09

  9. Cosmics use • 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 Xvc - TIPP09

  10. Correct channel mapping with comics Missing signal due to mapping error in software (may 2008) Corrected Xvc - TIPP09

  11. Trigger path validation with cosmics Wrong Trigger Cabling should deliver this Actually we had this Xvc - TIPP09

  12. Detector time alignement (muon vs calo) • Calo-triggered event Time slot Time slot • Muon-triggeredevent: Muon signal seen 2 clock cycles earlier Time slot Time slot 22/04/2008 Pascal Perret - LPC Clermont Xvc - TIPP09

  13. Time Alignment Strategy • 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 δTsampling δTsampling δTsampling 25 ns t Prev1 T0 Next1 Xvc - TIPP09

  14. ECAL / HCAL time alignment Within each detector the RMS of R is coherent with time aligned cells within 3 ns HCAL ECAL Xvc - TIPP09

  15. PS time alignment • Integration time is the same for 1 PMT(64 channels) PS aligned within 4ns Outer Middle Inner Xvc - TIPP09

  16. 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 Xvc - TIPP09

  17. Calorimeter Track Reconstruction • A tool has been developped to reconstruct tracks in the calorimeter • Determineazimuthal angle (φ) in HCAL & ECAL and combine them • Select eventswithχ²<15 • Selectedtracks are extrapolated for position & timing • PS/SPD • Othersubdetectors Xvc - TIPP09

  18. 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% Xvc - TIPP09

  19. PS calibration with cosmics • FromCosmicsevents : • Each PS regioncalibrated – using the time model of signals Xvc - TIPP09

  20. Injection tests events Connectics problems SPD PS Flow  0.1-1 MIP/cm2 Pascal Perret - LPC Clermont 3/09/2008 • SPD multiplicity was used as trigger for LHC synchronization tests • 1 injection test shot  3 h Cosmics • Coherent with cosmics results Xvc - TIPP09

  21. 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 ! Xvc - TIPP09

  22. Commissioning the LHCb calorimeters with cosmic rays Xavier Vilasis-Cardona On behalf of the LHCb calorimeter group 1st international conference onTechnology and Instrumentation in Particle Physics TIPP09-Tsukuba, Japan, March 2009 Xvc - TIPP09

  23. Backup Slides Xvc - TIPP09

  24. Photon – electron triggger path ECAL -> PS/SPD->TVB tested on cosmics Xvc - TIPP09

  25. 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 Clermont Xvc - TIPP09

  26. Time alignement PS/SPD & ECAL/HCAL # hits Prs #hits ECAL #hits SPD Bx #hits HCAL y y ECAL HCAL x Bx x # hits Prs #hits ECAL #hits SPD Bx #hits HCAL y y ECAL HCAL x Bx x Xvc - TIPP09

  27. HCAL & ECAL: Time Alignment Aout: 87k Event ECAL RMS(RMS R)=0.039 Improvement in the internal time alignment of the ECAL with the HV corrections HCAL Aout 29776 RMS(RMS R)=0.076 THCAL - TECAL Forward tracks – PP: Slope = 2.38 OffSet = -2.20 ns PP New Run 29 776 ΔL Pascal Perret - LPC Clermont 3/09/2008 Xvc - TIPP09

  28. Front End Electronics Xvc - TIPP09

  29. Calorimeter Trigger System Xvc - TIPP09

  30. LHCb DAQ System Xvc - TIPP09

  31. Cosmics in the calorimeter Xvc - TIPP09

  32. 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 ) Xvc - TIPP09

  33. 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 t0 (ns) t0 (ns) t0 (ns) 100 GeV PGun muons (SPD inner cell), 1k events, B off Threshold ~ 0.5 MIP Threshold ~ 0.25 MIP Xvc - TIPP09

  34. 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 Xvc - TIPP09

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