B-Physics Trigger Working Group Status Report

1. John Baines B-Physics TriggerWorking Group Status Report • Contents: • Developments since TDAQ week • Updates to execution times • LVL2 RoI Guidance to EF • Effect of pT thresholds on execution time • Effect of luminosity & thresholds on resource requirements • RoI Guided B-physics • Future Work • Conclusions http://hepunx.rl.ac.uk/atlasuk/simulation/level2/meetings/PESA270202/PESA.ppt PESA.pdf PESA.ps

2. History since Nov 2001 TDAQ week-1 • Set of parameters defined for Paper Model, results presented by Jos & Maris at November 2001 TDAQ week • Used to calculate resources for RoI and B-physics triggers at 1033 : Paper Model Results 2001 L = 1033 Note: Lower requirement of 90 - 120 processors for high lumi. menu at L=1034 • December 2001: • Update to parameters used to calculate resources for RoI triggers • No update to parameters for B-physics Trigger • Note “HLT Cost Model” sent out by Chris Bee • => Apparent large extra resource requirement for Bphysics Back of Envelope calculation used for Cost Model L = 1033 • Calculations for 2x1033 => ~factor 4 increase in CPU requirements for full-scan (2 x occupancy, 2 x rate) • Update parameters for FEX times • Examine different trigger scenarios and options for different luminosities Note: The resources needed to get the byte-stream data and convert it to objects are not included in the tables.

3. History since Nov 2001 TDAQ week-2 sin2b precision for 30fb-1 (3 yrs @ 1033 or 1.5 yrs @ 2x1033) TDR: 0.012 • December/January 2002: • Update FEX execution times • Consider possibilities for reduced B-physics programme: • Drop TRT at LVL2 (with loss of J/Y(ee) channel) • Increase single muon threshold to 8 GeV • Restrict running to when L = 1033 (second half of fills, poor fills, or if machine doesn’t initially meet expectations). • Don’t repeat full-scan at EF, use LVL2 RoI instead Back of Envelope calculation L = 1033 0.016 0.023 Changes summarized on following slides 0.032 ? February 2002: Preliminary paper model results with updated parameters: No.s in brackets are for different RoS schemes and incl. a 10ms overhead time for the RoI request Note: The resources needed to get the byte-stream data and convert it to objects are not included in the tables.

4. Execution Times - 4000 MHz Processor (160 SI95) http://www-winconsin.cern.ch/~atsaul/egamma/latest/ http://www-winconsin.cern.ch/~atsaul/egamma/latest/ Assumes TRT FEX run after SCT FEX Muon trigger: • Muon FEX : 0.2 ms (was 0.25) (ATL-DAQ-2000-036) 1 RoI/event (was 2) • Si-FEX : Update FEX time to 0.2 ms (was 4 ms) based on : • SctKalman time of 0.17 ms per TRT seed in B->mX events @ low lumi (ATL-DAQ-2000-031) • SctKalman time of 0.19 ms per LVL2 EM seed in jet events @ design lumi • SctHough time of 0.31 ms per LVL2 EM seed in jet events @ low lumi • Association of Si and Muon tracks - assumed small c.f. FEX time • MU8 trigger @ 1033=> 10 kHz input rate, 4 kHz after LVL2 mu, 2.5 kHz output rate changes c.f. previously rate x 0.43, time x 0.52, no. RoI x 0.5 rate x 0.44, time x 0.07 was 120 cpu incl. 72 for TRT-scan • Optionally TRT FEX could be run as well or instead of Si FEX - 2 alternative FEX: • TRT-LUT - 0.23 ms for EM RoI @ low lumi • TBTREC - 3.9 ms for EM RoI @ low lumi

5. Execution Times - 4000 MHz Processor (160 SI95) http://hpunx.rl.ac.uk/atlasuk/simulation/level2/Bphys/bmark.html ID-scan - Pixel Guided : • Pixel-Scan : 8 ms (was 5ms - now includes data preparation) • SiKalman : 4 ms based on pT>1.5 GeV & incl. data preparation (was 4 ms based on pT > 0.5 GeV, but no data prep.) Changes c.f. previously rate x 0.44, time x 1.6 rate x 0.44, time same was 180 cpu incl. 130 for TRT LUT and 8 to extrapolate tracks outwards OR TRT Guided : Two alternative FEX: Based on pT > 1.5 GeV Threshold Note: TRT-scan gives more seeds than Pixel Scan particularly TRT-LUT which doesn’t have a stage to combine tracks crossing Barrel-Endcap

6. EF Execution Times- 4000MHz Processor (160 SI95) LVL2 output rate xKalman - Full Scan • TRT - Guided 160 ms (as before) • Pixel - Guided 40 ms Previously 230 80 260 1000 incl. 370 for J/y(ee) • Changes w.r.t. previously : • Rate x 0.2, • Time x 0.25 (pixel guided, not TRT-guided) xKalman - RoI Guided. => RoI Guided reconstruction at the EF expected to be a Factor of 10 - 20 faster than full-scan Previously 160 cpu Assume 1 cpu required for Pixel-guided reconstruction in LVL2 RoI

7. Effect of full-scan pT threshold • Pixel-seeded LVL2 reconstruction: • TRT-seeded LVL2 reconstruction - xKalman TRT: • TRT-seeded LVL2 reconstruction - TRT LUT: All times for 4GHz PC 160 SI95

8. Effect of Threshold & Lumiosity Latest preliminary paper model results using the same input parameters: LVL2 cpu requirement for high lumi. running matches requirement incl. Bphysics at L=1033 Summary of Back-of-envelope calculations of cpu resources for 3 different scenarious: All numbers are for 4GHz PC (160 SI95) Note: Overheads for unpacking and creation of objects are not included. ATL-DAQ-2002-005 gives 86 ms for an event with similar occupancy as B->mX at 1033. Example: This would mean ~20 extra cpu at the EF for the mu8@1033 scenario.

9. RoI Guided B-Physics TP trigger menu based on LVL1 MU6 RoI plus ID full-scan at LVL2: m6 + m5 m6 + e5 m6 + B(pp) m6 + Ds(f(KK)p) m6 + J/y(ee) m6 : LVL1 ROI,m5: ID full-scan track extrapolated to muon detector e5: ID full-scan track extrapolated to muon detector B(pp), Ds(f(KK)p), J/y(ee) from tracks reconstructed by ID full0-scan Look into the possibility of using LVL1 RoI for B-physics triggers: (See Alan Watson’s talk at B-physics meeting) • m5: from muon RoI • e5: From LVL1 EM5 (ET>2 - 3 GeV) RoI confirmed in the ID at LVL2 • B(pp), Ds(f(KK)p) : from LVL1 JET RoI (ET > 5 GeV) • with LVL2 full-scan in RoIh x f~ 1.5 x 1.5 • J/y(ee) from LVL1 EM5 RoI with LVL2 full-scan in RoIh x f~ 1.5 x 1.5 Thresholds of pT>5GeV in the barrel and pT>3GeV in the endcaps seem possible. (See Leandro’s talk) Offers savings due to performing reconstruction in RoI only. The potential saving in CPU and the implications for efficiency have yet to be evaluated.

10. RoI Guided B-Physics 100 80 60 40 20 0 Example: Efficiency for Bs-> Ds(f(KK)p) events m pT > 6 GeV, |h|<2.5 Ds pT > 1 GeV, |h|<2.4 p pT > 1 GeV, |h|<2.5 Efficiency for matching (Dh, Df < 0.4) to an 8x8 jet RoI with ET>5 GeV as a function of Bs pT. Jet RoI ET> 5 GeV Efficiency (%) Fast Simulation 5 10 15 20 25 30 35 40 Bs pT (GeV) EM RoI ET> 2 GeV Example: Multiplicity for EM RoI ET > 2 GeV in B->mX events with m pT > 6 GeV Fast Simulation

11. Future Work • Descoping of ID may mean that at start-up : • 1 pixel layer is missing • TRT coverage extends only to | h | < ~1.8 (no long straws in end-cap) • Need to study the implications for efficiency and execution time. Two approaches: • Extend pixel-scan algorithm to include SCT information • Use alternative algorithm developed by Nikos Konstantinidis & Hans Dreverman • Evaluate performance of RoI guided B-physics. • Evaluate Implications of latest detector layout (esp. pixel layout changes). • TRT-scan is expensive in CPU resources, need to look at, instead, extending Pixel + SCT tracks into TRT at LVL2 (i.e. Si tracks seed TRT reconstruction).

12. Conclusions • A B-trigger scheme has been shown which could be accommodated within the CPU resources foreseen for RoI-based triggers at high luminosity. • Any descoping of the B-physics trigger has implications for the physics programme, e.g. loss of precision for sin2b measurement. • New ideas are being pursued : • Reconstruction at EF using LVL2 RoI • Reconstruction at LVL2 using low pT LVL1 EM and Jet RoI