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High Level Triggers for B Physics: Status and plans

High Level Triggers for B Physics: Status and plans. by Simon George for the HLT B-physics group. PESA group. Physics and Event Selection Algorithms algorithm development for high level triggers increased emphasis on event filter event selection strategy physics driven

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High Level Triggers for B Physics: Status and plans

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  1. High Level Triggers forB Physics:Status and plans by Simon George for the HLT B-physics group

  2. PESA group • Physics and Event Selection Algorithms • algorithm development for high level triggers • increased emphasis on event filter • event selection strategy • physics driven • DAQ/HLT Technical Proposal March 2000

  3. B-physics HLT group • Aim for TP is to demonstrate a viable B-physics trigger. • Criteria for performance evaluation: • pT(e) > 1 GeV • pT() > 4 GeV • pT(/K) > 1.5 GeV • Efficiency: absolute and w.r.t. offline selection • Rate for B  X + pile up events • Time on standard machine for B  X + pile up events • Other issues • LVL2/EF boundary • Architecture implications • Robustness w.r.t. occupancy (luminosity, noise)

  4. Current Status • Work is documented in TPSR, Phys TDR, ATLAS notes. • Mostly done with offline code: • LVL2 muon trigger (muon detector track, ID track, matching) • LVL2 tracking with modified Xkalman • e/h separation using ID track + TR + ECAL •  identification pT > 3 GeV using muon detector + barrel HCAL • Baseline concept has been demonstrated and strategies developed, but offline reconstruction is too optimistic • Emphasis now switching to development of more trigger-like algorithms

  5. Trigger Algorithms • TRT scan (LUT) • TRT scan • initial search from Xkalman • interesting alternative ‘unbinned’ search • Si Hough/histo/fit • Si Kalman • Pixel scan • Full Xkalman++ • reference algorithm for LVL2 • for integrated EF studies

  6. TRT scan with LUT • Hough transform to histogram in (1/pT, 0) space • transformations for each straw in lookup table for speed • track candidates = maxima in histogram • Performance •  pT > 1 GeV, || < 2.5  mean efficiency 85% • no. of track candidates high in overlap region • Timing results • P-II 300 MHz / FPGA 50 MHz • Data: bbX+mb (low lumi)

  7. Event Filter • Need to show cuts that reduce rate from LVL2 (~840 Hz) to 100 Hz. • Two approaches: • Start with inclusive triggers like LVL2, e.g. J/  e+e- • which cuts can be tightened? • new cuts? e.g. vertex, impact parameter • Start with offline cuts • which cuts could be loosened? • look for common selections inclusive EF selections • This will need close interaction with the B-physics group.

  8. Summary • B-physics trigger is a very active area of study • Working towards Technical Proposal • We will benefit from close contact with offline group. • Some projects may be of particular interest, e.g. • Trigger/Offline comparison • LVL2 muon/inner detector track association • Event Filter cuts • http://hepunx.rl.ac.uk/atlasuk/simulation/level2/Bphys

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