ATLAS ATLAS Week: 25/Feb to 1/Mar 2002 B-Physics Trigger Working Group Status Report PESA.pdf PESA.ps John Baines Contents: Developments since TDAQ week Updates to execution times LVL2 RoI Guidance to EF Effect of p T thresholds on execution time Effect of luminosity & thresholds on resource requirements RoI Guided B-physics Future Work Conclusions

ATLAS Week 25/Feb to 1/Mar Back of Envelope calculation used for Cost Model Paper Model Results 2001 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 : 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 L = Calculations for 2x10 33 => ~factor 4 increase in CPU requirements for full-scan (2 x occupancy, 2 x rate) Note: Lower requirement of processors for high lumi. menu at L=10 34 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.

ATLAS Week 25/Feb to 1/Mar Back of Envelope calculation February 2002: Preliminary paper model results with updated parameters: History since Nov 2001 TDAQ week-2 Note: The resources needed to get the byte-stream data and convert it to objects are not included in the tables. December/January 2002: Update FEX execution times Consider possibilities for reduced B-physics programme: Drop TRT at LVL2 (with loss of J/  (ee) channel) Increase single muon threshold to 8 GeV Restrict running to when L = (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 sin2  precision for 30fb -1 ( or 1.5 2x10 33 ) TDR : ? L = Changes summarized on following slides No.s in brackets are for different RoS schemes and incl. a 10  s overhead time for the RoI request

ATLAS Week 25/Feb to 1/Mar Execution Times MHz Processor (160 SI95) Muon trigger: Muon FEX : 0.2 ms (was 0.25) (ATL-DAQ ) 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->  X low lumi (ATL-DAQ ) –SctKalman time of 0.19 ms per LVL2 EM seed in jet design lumi –SctHough time of 0.31 ms per LVL2 EM seed in jet low lumi Association of Si and Muon tracks - assumed small c.f. FEX time MU => 10 kHz input rate, 4 kHz after LVL2 mu, 2.5 kHz output rate winconsin.cernhttp://www- winconsin.cern.ch/~atsaul/egamma/latest / Optionally TRT FEX could be run as well or instead of Si FEX - 2 alternative FEX: TRT-LUT ms for EM low lumi TBTREC ms for EM low lumi Assumes TRT FEX run after SCT FEX rate x 0.43, time x 0.52, no. RoI x 0.5 changes c.f. previously rate x 0.44, time x 0.07 was 120 cpu incl. 72 for TRT-scan

ATLAS Week 25/Feb to 1/Mar Execution Times MHz Processor (160 SI95) ID-scan - Pixel Guided : Pixel-Scan : 8 ms (was 5ms - now includes data preparation) SiKalman : 4 ms based on p T >1.5 GeV & incl. data preparation (was 4 ms based on p T > 0.5 GeV, but no data prep.) /level2/Bphys/bmark.html OR TRT Guided : Two alternative FEX: Based on p T > 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 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

ATLAS Week 25/Feb to 1/Mar EF Execution Times- 4000MHz Processor (160 SI95) xKalman - Full Scan TRT - Guided 160 ms (as before) Pixel - Guided 40 ms LVL2 output rate xKalman - RoI Guided. => RoI Guided reconstruction at the EF expected to be a Factor of faster than full-scan Assume 1 cpu required for Pixel-guided reconstruction in LVL2 RoI Previously incl. 370 for J/  (ee) Changes w.r.t. previously : Rate x 0.2, Time x 0.25 (pixel guided, not TRT-guided) Previously 160 cpu

ATLAS Week 25/Feb to 1/Mar Effect of full-scan p T threshold Pixel-seeded LVL2 reconstruction: TRT-seeded LVL2 reconstruction - xKalman TRT: TRT-seeded LVL2 reconstruction - TRT LUT: All times for 4GHz PC 160 SI95

ATLAS Week 25/Feb to 1/Mar Effect of Threshold & Lumiosity Summary of Back-of-envelope calculations of cpu resources for 3 different scenarious: Latest preliminary paper model results using the same input parameters: LVL2 cpu requirement for high lumi. running matches requirement incl. Bphysics at L=10 33 Note: Overheads for unpacking and creation of objects are not included. ATL-DAQ gives 86 ms for an event with similar occupancy as B->  X at Example: This would mean ~20 extra cpu at the EF for the 33 scenario. All numbers are for 4GHz PC (160 SI95)

ATLAS Week 25/Feb to 1/Mar Look into the possibility of using LVL1 RoI for B-physics triggers: RoI Guided B-Physics TP trigger menu based on LVL1 MU6 RoI plus ID full-scan at LVL2: (See Alan Watson’s talk at B-physics meeting)  6 +  5  6 + e5  6 + B(  )  6 + D s (  (KK)    6 + J/  (ee)  6 : LVL1 ROI,  5: ID full-scan track extrapolated to muon detector e5: ID full-scan track extrapolated to muon detector B(  ), D s (  (KK)   J/  (ee) from tracks reconstructed by ID full0-scan  5: from muon RoI e5: From LVL1 EM5 (E T >2 - 3 GeV) RoI confirmed in the ID at LVL2 B(  ), D s (  (KK)   from LVL1 JET RoI (ET > 5 GeV) with LVL2 full-scan in RoI  x  ~ 1.5 x 1.5 J/  (ee) from LVL1 EM5 RoI with LVL2 full-scan in RoI  x  ~ 1.5 x 1.5 Thresholds of p T >5GeV in the barrel and p T >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.

ATLAS Week 25/Feb to 1/Mar Example: Efficiency for B s - > D s (  (KK)  ) events  p T > 6 GeV,  2.5 D s p T > 1 GeV,  2.4  p T > 1 GeV,  2.5 Efficiency for matching (  ,   5 GeV as a function of B s p T B s p T (GeV) RoI Guided B-Physics Efficiency (%) Example: Multiplicity for EM RoI E T > 2 GeV in B->  X events with  p T > 6 GeV Jet RoI E T > 5 GeV EM RoI E T > 2 GeV Fast Simulation

ATLAS Week 25/Feb to 1/Mar Future Work Descoping of ID may mean that at start-up : 1 pixel layer is missing TRT coverage extends only to |  | < ~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).

ATLAS Week 25/Feb to 1/Mar 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 sin2  measurement. New ideas are being pursued : Reconstruction at EF using LVL2 RoI Reconstruction at LVL2 using low p T LVL1 EM and Jet RoI