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Status of J/  Trigger Simulations for d+Au Running

Status of J/  Trigger Simulations for d+Au Running. Trigger Board Meeting Dec5, 2002 MC & TU. Simulations & Datasets. Background Studies: HIJING d+Au, min bias, plain GSTAR simulations: 90k events Full BEMC was in but only ½ used J/ : 1 decay in e+e-/event + GSTAR: 100k events

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Status of J/  Trigger Simulations for d+Au Running

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  1. Status of J/ Trigger Simulations for d+Au Running Trigger Board Meeting Dec5, 2002 MC & TU

  2. Simulations & Datasets • Background Studies: • HIJING d+Au, min bias, plain GSTAR simulations: 90k events • Full BEMC was in but only ½ used • J/: • 1 decay in e+e-/event + GSTAR: 100k events • flat in rapidity and pT • using simple generator for y and pT • Gaussian y distribution (s = 1) • Exponential in pT (slope 600 MeV/c) • Use GSTAR data from BEMC, BBC only

  3. Assumptions for Run Conditions • d+Au Collisions: • L = 1 1028 cm-2 s-1 • sinel = 2.3 b • Interaction Rate = 23 kHz • 5.3 10-6 J/ into e+e- in one unit at midrapidity • 41 10-6 J/ into e+e- total • L2 runs with 1kHz • ADCs of all towers available • calibration ADC  E available • BBC timing info available  rough vertex z • L0 • one EMC patch > threshold • patch = 4x4 towers • available: patch sum and highest tower in patch • optional (?): count of patches above threshold

  4. BBC triggered events all HIJING events L0 Simulation Results I • BBC triggers fires in 93% of all min bias HIJING events  21 kHz BBC rate

  5. J/Y Acceptance • Acceptance = Both Electrons with pMC>1 hit a BEMC tower. • Accepted/Thrown = 0.051 • Accepted (in 0< h < 1) /Thrown (in 0 < h < 1 ) = 0.114 Accepted Raw (input)

  6. L0 Simulation Results II • How many patches in the event have high tower > 1 (1.5) GeV ? Rejection power of non-J/ events J/  efficiency (wrt those in acceptance)

  7. L2 Trigger: Getting the invariant mass quickly • p1 = (EEMC-12-m2)½  EEMC • p2 = (EEMC-22-m2)½  EEMC • cos q = x1x2/(|x1| |x2|) • m2 2 p1 p2 (1 – cos q) • Pro: • simple, fast (no trig function) • avoids ambiguity

  8. L2 Energy Resolution no clustering single tower • Cluster 3 highest towers in a 3x3 patch • 2 tower vs. 3 tower cluster: L2 Mass RMS changes from 668 to 311 MeV 3 tower cluster Resolution ~ 17%/E <Ee - Ecl> = 40 MeV RMS = 248 MeV 3 tower cluster Conclusion: need clustering algorithm for L2 optimum: 3 tower cluster

  9. cos q Resolution J/ flat in h and pt J/ realistic kinematics

  10. Thrown mass L2 Mass, real E, real cos(q) L2 Mass, cluster E, real cos(q) L2 Mass, real E, cluster cos(q) L2 Mass, cluster E and cos(q) L2 Mass Resolution • Several contributions: • Mass approximation • Negligible • Cluster Energy • RMS = 248 MeV • Cluster cos(q) • ~tails • Realistic simulations: • RMSmass = 311 MeV • 99.9% contained in 31 GeV mass window Here:MC z-vertex used (know from earlier studies that effect is small)

  11. L2 Simulation Results • How many tower pairs in the event have mass > 1 , 1.5, 2 GeV ? Rejection power of non-J/ events J/  efficiency (w.r.t. those in acceptance) Note: factors independent of 1 or 2 patch L0 trigger but NOT L0 rate

  12. L2 Mass & Cos(q), Background • L2 Mass cut reduces background, keeps efficiency at ~70% • Note correlation between mass and opening angle: • lowest mass pairs must come from cos (q) ~ 1

  13. All BG towers Photons Pions Kaons Protons Next Step: Isolation Cuts? • Try to exploit shower topology. Electromagnetic showers should deposit their energy mainly in one tower. electrons background

  14. Trigger and Sample Rates • Input: • 41  10-6 21 kHz = 0.86 Hz • in acceptance: 0.86 Hz  0.051 = 44  10-3 Hz • L0 with 1 GeV cut: • 1 patch: 21 kHz/4.8 = 4.4 kHz event rate • 2 patch: 21 kHz/24 = 0.9 kHz event rate • L2 (1 kHz): • 1kHz/2 (rejection) = 500 Hz L2 trigger rate • 1 patch: 1kHz/4.4kHz  23% • 2 patch: 100% • J/ rate after L2: • 1 patch: 44  10-3 Hz  0.23  0.7  50/500 = 0.7  10-3 Hz • 2 patch: 44  10-3 Hz  0.7  50/500 = 3  10-3 Hz • for 106 sec  700 – 3000 J/ s

  15. Conclusions • Prospects for J/Y Trigger look promising • Achieve reasonable efficiency at L0 and L2 • Tower Energy > 1 GeV, L2 Mass > 2 GeV gives • r ~ 24 at L0 (recall BBC rates is ~21 kHz) • r ~ 50 at L0 & L2, (simple Mass threshold increases r x 2) • L2 eff ~ 70% • Statistical gain of 25 over no trigger case. • Steps to finalize algorithm: • Isolation cuts (3x3 sum tested, 5x5 sum, 7x7 sum ?) • Test 2 Different Tower Thresholds, e.g. Tower1>1.5, Tower2>1 GeV • Implement trigger in L2 CPU’s next week • Note: Trigger fits in very nicely with Jeff’s proposed trigger scheme. • Worth reiterating: already a proof-of-principle would teach us a lot!!

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