1. ATLAS ATLAS PESA Meeting 25/04/02 B-Trigger Working Group Status Report This talk: http://hepunx.rl.ac.uk/atlasuk/simulation/level2/meetings/pesa250402/PESA.ppt http://hepunx.rl.ac.uk/atlasuk/simulation/level2/meetings/pesa250402/PESA.ps http://hepunx.rl.ac.uk/atlasuk/simulation/level2/meetings/pesa25040202/PESA.pdf John Baines Progress on Algorithms Updates to benchmarking & resource estimates Using Calorimeter information to guide LVL2 B-triggers Summary

2. ATLAS PESA Meeting 25/04/02 2 Progress on Algorithms IDscan (SCT & Pixels): (Nikos Konstantinidis, Hans Drevermann) Confirmed that IDscan algorithm: - see Nikos' talk. Reproduces TP B-trigger performance (10% - 15% better effic. for D s (  ) trigger) Gives same performance for reduced layout - 2 instead of 3 barrel Pixel layers Execution time: 6 ms scaled to a 4GHz 160 SI95 machine, 11 ms including Si data preparation Pixel-scan expected to achieve similar execution time (currently longer) PixTrig: (Genova) Currently working to reproduce TP results in Athena framework Will then modify algorithm to include SCT info. Plan to look at linear fit in transform space, as used by CDF, as alternative to SiKalman to see if it gives better performance.

3. ATLAS PESA Meeting 25/04/02 3 Benchmarking & Resource Estimates Updated resource estimates reported at last ATLAS week Benchmarking since redone to measure mean, m 50 and m 95 times for - full-scan in B - >  X events http://hepunx.rl.ac.uk/atlasuk/simulation/level2/Bphys/bmark.html - EM RoI  x  = 0.2 x 0.2 in dijet events with/w.o. pile-up http://hepunx.rl.ac.uk/atlasuk/simulation/level2/eid/bmark.html Later used to estimate muon confirmation times. Parameters and estimates documented in ATLAS note : ATL-COM-DAQ-2002-nnn Jos has re-run paper model using these parameters as input: http://www.nikhef.nl/pub/experiments/atlas/daq/paper-para-overview1.pdf

4. ATLAS PESA Meeting 25/04/02 4 Benchmarking & Resource Estimates Note: In order to save cpu resources, not using TRT info at LVL2: => No J/psi(e,e) trigger Resources required at EF small compared with LVL2 (~few cpu) assuming: xKalman starting with pixels and guided by Level-2 RoI (see presentation at previous meeting) 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

5. ATLAS PESA Meeting 25/04/02 5 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: http://www.ep.ph.bham.ac.uk/user/atw/bmeet/B-roi-feb02.ppt 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 Ds(  ) 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

6. ATLAS PESA Meeting 25/04/02 6 Future Work Calorimeter RoI guidance for B-triggers: Need to confirm results with full simulation. Requires : Simulation of: Level-1 EM/Tau trigger algorithm - done (Ed Moyse) Level-1 Jet trigger algorithm - underway (Ed Moyse) Level-1 electronics (noise) - who? Generation of simulated data : single particles for calibration B - >  X events signal channels : B - > , B->J/  (ee), B - > D s (  (KK)  ) min. bias Addition of pile-up (including pulse history in ECAL). Calibration of ECAL energies Level-1 studies - Optimisation of thresholds B-trigger performance studies Verification / optimisation of algorithms with latest layout : Requires: New datasets (including pile-up) Algorithms able to read new datasets (LVL2 & EF) B-trigger studies including muon trigger. Requires: New datasets including muon simulation Muon algorithms available in new framework (LVL2 & EF)

7. ATLAS PESA Meeting 25/04/02 7 Summary Encouraging progress with IDscan algorithm Converging on a baseline B-trigger strategy minimising resource requirements Encouraging preliminary results for RoI guided B-trigger at Level-2 => potential to futher reduce resource requirements, but with reduced efficiency A lot of work on hold awaiting new data and software : RoI guided B-physics inclusion of muon trigger verification/optimisation of algorithms for latest layout Timescales tight even with a 6 month delay in the TDR