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Hera-B trigger Teresa N úñ ez - DESY HH

Hera-B trigger Teresa N úñ ez - DESY HH. The Hera-B experiment General Trigger overview 2002 base line trigger Trigger performance Trigger rates Trigger efficiency Physics implications Summary. The Hera-B experiment. Physics program for 2002:.

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Hera-B trigger Teresa N úñ ez - DESY HH

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  1. Hera-B triggerTeresa Núñez - DESY HH The Hera-B experiment General Trigger overview 2002 base line trigger Trigger performance Trigger rates Trigger efficiency Physics implications Summary Hera B trigger Teresa Núñez DESY-HH

  2. The Hera-B experiment Physics program for 2002: J/Y oriented trigger • Improvement in bb cross section • measurement • Charmonium studies: J/Y and cc spectra • J/Y suppression • Ratio of charmonium states B0 J/Y X 920 GeV Hera B trigger Teresa Núñez DESY-HH

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

  4. General Trigger overview Multilevel trigger system 10 (5) MHz Pretrigger/Level 1 (rej. 200-100) 10 ms 50 KHz Level 2 (rej. 700) 8 ms 50 Hz Full online reconstruction and logging to tape 4 s Hera B trigger Teresa Núñez DESY-HH

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

  6. 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 Hera B trigger Teresa Núñez DESY-HH

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

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

  9. Level 2 Add two main tracking stations Seeded by Level 1 tracks Add vertex information Four stations of main tracking system Hera B trigger Teresa Núñez DESY-HH

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

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

  12. Level 2 algorithm L2magnet: transport trough field Reduce RoI size First tracking station before the magnet Hera B trigger Teresa Núñez DESY-HH

  13. Level 2 algorithm L2sili: ‘Kalman filter’ algorithm Add track precision Si-strip vertex detector Hera B trigger Teresa Núñez DESY-HH

  14. Level 2 algorithm L2vertex: Require common vertex for track pairs Hera B trigger Teresa Núñez DESY-HH

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

  16. 2002 base line trigger Cover full detector acceptance … despite the fact that … no inner tracking in Level 1 • Single lepton at Level 1: • kinematical cuts (pt) • Double lepton at Level 2: • Level 1 and pretrigger seeds … other option: 2 track at Level 1 (only in outer tracking) being considered Hera B trigger Teresa Núñez DESY-HH

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

  18. Trigger rates Setting Level 1 cuts … Level 1 output rate limited by data-transfer through Level 2 switching network (~ 50kHz) 102 Trigger rates (kHz) 10 • Pt cut 0.7 GeV 1 102 102 • Pt cut 1.4 GeV 10 Trigger rates (kHz) 1 • Identification of Brems. g (improve e+e- purity and reduce rate) 0.5 0.75 1. 1.25 1.5 1.75 2. 2.25 2.5 Pt cut in the Level 1 (GeV) Hera B trigger Teresa Núñez DESY-HH

  19. Trigger rates 5 MHz IR Logging rate limit 125 Hz Pt > 0.7 GeV 107 Muon channel Trigger rates (Hz) 106 Electron channel 50 Hz with full ONLINE reconstruction 105 29 kHz 104 If needed: 2GeV invariant mass cut (>50% rate drop) 103 1.6 kHz 60 Hz 102 40 Hz Level 1 2nd trk Slicer RefitX RefitY L2Sili L2Vert IR Hera B trigger Teresa Núñez DESY-HH

  20. Trigger rates 10 MHz IR Pt > 1.4 GeV In addition … 107 Muon channel • VETO of high multiplicity events: • RICH occupancy • ECAL energy deposition Trigger rates (Hz) 106 Electron channel 28 kHz 105 104 Decreases the output rate by a factor 2 103 2.3 kHz 102 40 Hz Allows relaxing the pt cut 30 Hz IR Level 1 2nd trk Slicer RefitX RefitY L2Sili L2Vert Hera B trigger Teresa Núñez DESY-HH

  21. Trigger efficiency Sample: • 2·104 MC J/Y events: J/Y ee J/Ymm • with <1> inelastic interaction • Ideal detector performance <1> 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) Hera B trigger Teresa Núñez DESY-HH

  22. Trigger efficiency Pt > 0.7 GeV 0.5 Muon channel efficiency For Pt > 1.4 GeV: drop of 30 (50)% for J/y->mm(ee) efficiency 0.4 Electron channel 0.3 19.9% 0.2 High multiplicity VETO would allow a lower pt cut 3.2% 0 Level 1 Brems. Seeding Tracking Vertex Geo Hera B trigger Teresa Núñez DESY-HH

  23. Physics implications J/Y’s per hour: Assuming 2·103 hours (~ 1 year with deadtime) and 5 MHz … Trigger efficiency highly dependent on detector performance. Best estimation of this effect: factor 2 drop. Hera B trigger Teresa Núñez DESY-HH

  24. Physics implications Improvement bb cross section: • Reduce the error to systematics (15%) • Extract cross section from full reconstructed B mesons Hera B trigger Teresa Núñez DESY-HH

  25. Physics implications Charmonium studies: First charmonium spectra in negative XF cc production dependence on atomic number spA = spN Aa J/Y suppression Rc s(cc J)·Br(cc JJ/Yg) Rc= s(J/Y)tot CDF pp Ratio of charmonium states XF Hera B trigger Teresa Núñez DESY-HH

  26. Some comparisons … J/Y -> mm efficiency: • Main improvements with respect to 2000: • expected better performance of chambers in muon and main tracking systems • Level 1 algorithm • m-tracking at Level 2 for pretrigger seeds Factor 2 below design in algorithm efficiency but … perhaps the design was a bit näive Hera B trigger Teresa Núñez DESY-HH

  27. Requiring two leptons at Level 1(option under study) • Double lepton at Level 1: • pt cut at 0.5 GeV • mass cut 2GeV • no inner tracking • Double lepton at Level 2: • only Level 1 seeds Comparison to baseline scenario • Rates: • No problems in Level 1 output rate • (with lower Pt 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) Overall yields aproximately equivalent Both options are implemented in hardware and software Hera B trigger Teresa Núñez DESY-HH

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

  29. 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 Hera B trigger Teresa Núñez DESY-HH

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