ATLAS PESA Meeting 20/11/02 1 B-Physics Trigger in the TDR Demonstrate viable & affordable B-physics trigger based on the evaluation of two strategies: 1) Di-muon trigger at L=2x10 33, introducing full scan at lower luminosity 2) RoI guided B-trigger, possibly with addition of full-scan at lower luminosity Define 2 as baseline???? To do this need measurements of: Efficiency for signal channels Rate c.p.u resource estimate based on test-bed measurements for whole chain.

ATLAS PESA Meeting 20/11/02 2 Status of di-muon & full-scan triggers Current Status: Full-scan based strategy studied in detail using fully-simulated events and appropriate LVL2 and EF algorithms and documented in TP back-up document: ATL-DAQ Robustness of selection w.r.t. ID misalignment studied & documented in: ATL-DAQ EF selections documented: Rejection of rate at EF for J/ , D s and B 0 d - >  channels. (Moscow) ATL-DAQ Event Filter Rate for the D s Trigger (Innsbruck) ATL-DAQ Impact of only having 2 pixel layers at start-up studied using IDscan LVL2 algorithm Estimates exist for LVL1 di-muon rates and EF rates after J/  (  ) and B - >  X trigger selections Required c.p.u. resources have been estimated based on measured rates and executions times and documented in: ATL-COM-DAQ Algorithms : LVL2:  Fast (barrel only), Pixel-scan+sctKalman, IDscan, TRT-LUT, xKalmanTRT EF: xKalman, muon-? (for resource calculations assume  Fast re-run at EF) 1) Di-muon trigger at L=2x10 ^33, introducing full scan at lower luminosity

ATLAS PESA Meeting 20/11/02 3 Benchmarking & Resource Estimates Note: Based on custom-LVL2 algorithms, light-weight EDM, excludes data access overheads Most B-trigger resources required for LVL2 full-scan In order to save cpu resources, estimate does not include TRT at LVL2: => No J/psi(e,e) trigger EF Resources required at EF small compared with LVL2 (~few cpu) assuming: xKalman starting with pixels and guided by Level-2 RoI neglecting resources needed for muon reconstruction at EF Current offline muon algorithms too costly in cpu : => Only includes muons at LVL2 reconstructed by  Fast Preliminary paper model results (April 2002): Min. Farm size needed at startup Min. size incl. B-physics Difference ~25 c.p.u Final Farm size B-trigger resource estimate: ATL-COM-DAQ LVL2

ATLAS PESA Meeting 20/11/02 4 Using Calorimeter RoI to guide B-physics Triggers Preliminary studies of using low E T RoI to define regions to search ID at LVL2 (Alan Watson) Uses fast simulation : ATLFAST + parameterised calorimeter simulation Initial results encouraging, see Alan Watson’s talk: EM RoI E T >2 : for J/  (ee) and muon-electron triggers Mean Multiplicity = 1.1 (B - >  X,  p T > 6 GeV) Effic. to tag both e in J/  (e,e) : 80% (e p T >3 GeV) Jet RoI (0.8 x 0.8 cluster) E T >5 : for B(  ) and D s (  ) Mean Multiplicity = 1.7 (B - >  X,  p T > 6 GeV) Efficiency B   p T   4 GeV RoI E T  5 GeV B  D s  p T Ds,   1 GeV RoI E T  5 GeV LVL2 reconstruction inside RoI  potential to save ~factor 10 in execution time c.f. full-scan  but with lower efficiency Actual efficiencies and cpu savings depend on thresholds & multiplicities => need full simulation