Santiago de Compostela Beauty 2002 Hera B trigger Teresa Núñez DESY-HH Hera-B trigger Hera-B trigger Teresa Núñez - DESY HH The Hera-B experiment General Trigger overview 2002 base line trigger Trigger performance Trigger rates Trigger efficiency Physics implications Summary

Santiago de Compostela Beauty 2002 Hera B trigger Teresa Núñez DESY-HH The Hera-B experiment J/  oriented trigger Improvement in bb cross section measurement Charmonium studies: J/  and  c  spectra J/  suppression Ratio of charmonium states Physics program for 2002: B 0 J/  X 920 GeV

Santiago de Compostela Beauty 2002 Hera B trigger Teresa Núñez DESY-HH The Hera-B experiment pN interactions in Hera proton beam p(920GeV) + 10MHz Dense environment Low latency and high bandwidth Low S/B ratio  (J/  )/  (inel.)~3·10 -5 Highly selective and efficient Trigger challenge: Multiwire target with different materials Target + SVD Magnet Electromagnetic calorimeter Muon tracking system Main tracking system RICH

Santiago de Compostela Beauty 2002 Hera B trigger Teresa Núñez DESY-HH General Trigger overview Multilevel trigger system 10 (5) MHz 50 KHz 50 Hz 10  s 4 s 8 ms Full online reconstruction and logging to tape Pretrigger/Level 1 (rej ) Level 2 (rej. 700)

Santiago de Compostela Beauty 2002 Hera B trigger Teresa Núñez DESY-HH Pretrigger Charged lepton ID devices Two last tracking stations of MUON system Electromagnetic calorimeter Define RoI for Level 1 seeding

Santiago de Compostela Beauty 2002 Hera B trigger Teresa Núñez DESY-HH Level 1 and Level 2 Simplified Kalman filter algorithms based on Regions of Interest Main differences both trigger levels: Hardware implementation: Level 1 -> custom-made pipeline processor network Level 2 -> farm of 240 PCs Use of detector components: Level 1 -> four main tracking stations Level 2 -> add two tracking stations + vertex

Santiago de Compostela Beauty 2002 Hera B trigger Teresa Núñez DESY-HH Level 1 Three tracking stations of MUON system Four stations of main tracking system Main tracking: Outer part -> honey comb drift chambers Inner part -> MSGC + GEM

Santiago de Compostela Beauty 2002 Hera B trigger Teresa Núñez DESY-HH Level 1 hardware  60 Track Finding Units (TFUs) 500 M tracks/sec without deadtime Inputs: 1Tbit/s from tracking chambers (stored in 128 pipeline -> 10  s latency) RoI from previous layer of TFUs  3 Track Parameter Units  1 Trigger Decision Unit Muon pret. Ecal pret. TFUs TPUs TDU Muon candidate Electron candidate magnet target ECAL Muon stations Main tracking stations

Santiago de Compostela Beauty 2002 Hera B trigger Teresa Núñez DESY-HH Level 2 Four stations of main tracking system Add two main tracking stations Add vertex information Seeded by Level 1 tracks

Santiago de Compostela Beauty 2002 Hera B trigger Teresa Núñez DESY-HH Level 2 algorithm x view layers of main tracking stations behind the magnet Slicer: ‘Hough transformation’ Fast ghost removal

Santiago de Compostela Beauty 2002 Hera B trigger Teresa Núñez DESY-HH Level 2 algorithm x and stereo view layers of main tracking stations behind the magnet Refit X/Y: Simplified ‘Kalman filter’ Refine track parameters

Santiago de Compostela Beauty 2002 Hera B trigger Teresa Núñez DESY-HH Level 2 algorithm First tracking station before the magnet L2magnet: transport trough field Reduce RoI size

Santiago de Compostela Beauty 2002 Hera B trigger Teresa Núñez DESY-HH Level 2 algorithm L2sili: ‘Kalman filter’ algorithm Add track precision Si-strip vertex detector

Santiago de Compostela Beauty 2002 Hera B trigger Teresa Núñez DESY-HH Level 2 algorithm L2vertex: Require common vertex for track pairs

Santiago de Compostela Beauty 2002 Hera B trigger Teresa Núñez DESY-HH DAQ/Level 2 layout 1.3 GHz High flexibility High bandwidth and low latency switching network Event fully processed in one node with access to the complete detector information 8 ms

Santiago de Compostela Beauty 2002 Hera B trigger Teresa Núñez DESY-HH 2002 base line trigger Cover full detector acceptance no inner tracking in Level 1 Single lepton at Level 1: kinematical cuts (p t ) Double lepton at Level 2: Level 1 and pretrigger seeds … despite the fact that … … other option: 2 track at Level 1 (only in outer tracking) being considered

Santiago de Compostela Beauty 2002 Hera B trigger Teresa Núñez DESY-HH Trigger performance MC samples assuming ideal detector performance Trigger cuts constrained by rate handling Define cuts Study efficiency Level 2: Same machinery that is used online Level 1: Full bit level simulation

Santiago de Compostela Beauty 2002 Hera B trigger Teresa Núñez DESY-HH Trigger rates Level 1 output rate limited by data-transfer through Level 2 switching network (~ 50kHz) Setting Level 1 cuts … Identification of Brems.  (improve e+e- purity and reduce rate) Pt cut 1.4 GeV Pt cut 0.7 GeV Trigger rates (kHz) Pt cut in the Level 1 (GeV)

Santiago de Compostela Beauty 2002 Hera B trigger Teresa Núñez DESY-HH Trigger rates 5 MHz IR Muon channel Electron channel 40 Hz 60 Hz 29 kHz 1.6 kHz Logging rate limit 125 Hz 50 Hz with full ONLINE reconstruction If needed: 2GeV invariant mass cut (>50% rate drop) P t > 0.7 GeV Trigger rates (Hz) IR Level 12 nd trkSlicerRefitXRefitYL2SiliL2Vert

Santiago de Compostela Beauty 2002 Hera B trigger Teresa Núñez DESY-HH Trigger rates 28 kHz 2.3 kHz 30 Hz 40 Hz 10 MHz IR Muon channel Electron channel P t > 1.4 GeV VETO of high multiplicity events: RICH occupancy ECAL energy deposition Decreases the output rate by a factor 2 Allows relaxing the p t cut Trigger rates (Hz) IR Level 12 nd trkSlicerRefitXRefitYL2SiliL2Vert In addition …

Santiago de Compostela Beauty 2002 Hera B trigger Teresa Núñez DESY-HH Trigger efficiency Sample: 2·10 4 MC J/  events: J/  ee J/    with inelastic interaction Ideal detector performance corresponds to 10MHz IR (worst conditions) Only slightly dependence of the efficiency on the number of inelastic interactions ( less than 2% from 0 to 2 interactions)

Santiago de Compostela Beauty 2002 Hera B trigger Teresa Núñez DESY-HH Trigger efficiency Muon channel Electron channel 19.9% 3.2% P t > 0.7 GeV efficiency Geo Level 1Brems. SeedingTrackingVertex High multiplicity VETO would allow a lower p t cut For Pt > 1.4 GeV: drop of 30 (50)% for J/  ->  (ee) efficiency

Santiago de Compostela Beauty 2002 Hera B trigger Teresa Núñez DESY-HH Physics implications Assuming 2·10 3 hours (~ 1 year with deadtime) and 5 MHz … Type of eventJ/    J/   eeTotal J/  6.8· · ·10 6  c  J/  8.3· · ·10 5  2.7· · ·10 5 B7.6· · ·10 2 Trigger efficiency highly dependent on detector performance. Best estimation of this effect: factor 2 drop. J/  ’s per hour: IA rateMuon channelElectron channel 5 MHz (pt>0.7 GeV) MHz (pt>1.4 GeV)

Santiago de Compostela Beauty 2002 Hera B trigger Teresa Núñez DESY-HH Physics implications Improvement bb cross section: Reduce the error to systematics (15%) Extract cross section from full reconstructed B mesons

Santiago de Compostela Beauty 2002 Hera B trigger Teresa Núñez DESY-HH Physics implications Charmonium studies: RR XFXF  pA =  pN A  First charmonium spectra in negative X F CDF pp R=R=   (  c J )·Br(  c J  J/   )  (J/  tot  c production dependence on atomic number J/  suppression Ratio of charmonium states

Santiago de Compostela Beauty 2002 Hera B trigger Teresa Núñez DESY-HH Some comparisons … Trigger step expectationDesign Geometry33%44.5%62% Level 136%65.2%100% Level 211%69.4%90% Total1.3%19.9%51% J/  ->  efficiency: Main improvements with respect to 2000: expected better performance of chambers in muon and main tracking systems Level 1 algorithm  -tracking at Level 2 for pretrigger seeds Factor 2 below design in algorithm efficiency but … perhaps the design was a bit näive

Santiago de Compostela Beauty 2002 Hera B trigger Teresa Núñez DESY-HH Requiring two leptons at Level 1 (option under study) Double lepton at Level 1: p t cut at 0.5 GeV mass cut 2GeV no inner tracking Double lepton at Level 2: only Level 1 seeds Rates: No problems in Level 1 output rate (with lower P t cut) Present Level 2 rejection too small Efficiency: No improvement in muon channel (no inner detector in trigger) Improvement in electron channel (no brems. requirement) Comparison to baseline scenario Both options are implemented in hardware and software Overall yields aproximately equivalent

Santiago de Compostela Beauty 2002 Hera B trigger Teresa Núñez DESY-HH Summary Rejection versus efficiency: Note: final numbers require real data (including detector performance).  channel: rejection adequate efficiency ~45% (design 90%) e channel: need brems. requirement for adequate rejection efficiency ~12% (59% without brems.)

Santiago de Compostela Beauty 2002 Hera B trigger Teresa Núñez DESY-HH Summary Considerable improvements in trigger performance, since 2000 data taking, expected: Trigger system is ready for last commissioning steps. -> better trigger algorithms -> improved detector performance