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 Trigger for Run 8

 Trigger for Run 8. Rates, Yields, Backgrounds… Debasish Das Pibero Djawotho Manuel Calderon de la Barca Analysis Meeting BNL October 16, 2007. Prospects for  in Run 8. p+p 30 pb-1 sampled luminosity Run 6: 9.2 pb -1 sampled, S/B~ 1 : 2.31 Physics goals:

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 Trigger for Run 8

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  1.  Trigger for Run 8 Rates, Yields, Backgrounds… Debasish Das Pibero Djawotho Manuel Calderon de la Barca Analysis Meeting BNL October 16, 2007

  2. Prospects for  in Run 8 • p+p • 30 pb-1 sampled luminosity • Run 6: 9.2 pb-1 sampled, S/B~ 1 : 2.31 • Physics goals: • Improved yield (stat. error can go down by ~2) • pT spectrum? • Needs Seff~80, or ~450 counts (Seff~40 in |y|<0.5). • dAu • minbias s = 2.2 b. • rare processes: • s = spp x (2·197)a • peak: L = 30x1028 cm-2 s-1, • rate = 660 kHz (pileup!!) • L Delivered: 120 nb-1 • L Sampled: • Fast Detectors : 60 nb-1 • Slow Detectors : 30 nb-1 • Physics goals: • Yield, RdAu pT integrated • Needs 100-200 counts in |y|<0.5

  3. (Final?) Numbers from 2006 • Trig ID 117602 + 137603 • S = 175 • B = 405 • Seff = 31.1 • Seff = 5.58 • εϒ = 0.094 • dy=2.0 • Ldt = 9.23387 pb-1 • BR × dy/dσ = 100.808 pb • Note: signal above in dy=2 • in dy=1; S=87.5, Seff = 16

  4. Upsilon Estimates for Run 8 • With how much bandwidth? • pp Rejection • Run 6: 10 Hz / 550kHz • rejection factor : 55000 • Trigger rate Run 8 pp : 1.5 MHz/55000 = 27 Hz peak • Au Au Run 7 : 10 Hz / 25kHz (<Nbin>=235) • rejection factor : 2500 • Assumption: rejection decreases linearly with increasing <Nbin> • dAu <Nbin> = 17 • estimated rejection factor : 51000 • Trigger rate Run 8 dAu : 660 kHz/51000 = 13 Hz peak • What can we get? • BR x ds/dy = 91 pb @ 200 GeV. • Efficiency : • Geometrical Acceptance: 26% • L0 Efficiency : 93% • L2 Efficiency : 86% • Offline electron pair efficiency : 47% • Total =9.4%, use ~10% • Yields: • pp: • 30 pb-1 x 91 pb x 10% = 273 ’s • dAu: • 60 nb-1 x 91 pb x (2·197)0.95 x 10% = 160 ’s

  5. Options to decrease rate • Focus on p+p case (27 Hz is the most bandwidth requested!) • Reductions in p+p can be carried over to d+Au case. • Raising Cluster Energy of High-energy electron • Advantage: • Rate goes down quickly with higher E. • Disadvantage: • So does the efficiency… • Hits low-pt  hardest. • Cutting tighter on opening angle • Advantage: efficiency does not drop dramatically • Disadvantage: • Rate does not decrease dramatically either • Hits high-pt  hardest • Vertex cuts? • Almost the same as a prescale. • Some Differences: • For previous runs, tight vertex could help with Brems. of electrons • With low material in 2008, Brems. not so much of an issue. • It can still help with analysis offline, tracks will be close to center, many hits.

  6. Upsilon L2 parameters

  7. Raising “f0” (E of leading-e) • For 4<Et<6, Rejection increases decreases exponentially • Slope independent of multiplicity • Should also hold true for E of high energy cluster at L2

  8. Estimate Signal Reduction • Plot is for Et of tower at L0 • Cluster energy at L2 should show similar dependence. • Take value at 4.5 GeV to be baseline (~ threshold used in Run VI and Run VII) • Calculate reduction in signal relative to 4.5 GeV. • Calculate Seff = S/(2*(B/S)+1) to compare.

  9. Estimate Reduction in Rate • Rejection depends exponentially with Et • See blue lines • Slope is independent of multiplicity • Minbias & Central Au+Au have same slope • Use fit to rejection to estimate rate reduction • Caveat: • Rate reduction does not equal offline background. • Rate: photons and electron combinations • Offline background: electron combinations • Assume offline background also decreases, but with half the slope.

  10. E threshold, Rate Reduction

  11. pt vs Cos(q) • With good cos(q) determination, at cos(q)<0.4 we only lose pt>6 GeV. • Issue is resolution.

  12. From 2006 Offline data • Nominal cut has been at cos(q)=0 • Seff drops linearly with cos(q) • How much tighter can we live with?

  13. cos(q), Rate Reduction

  14. Other possibilities? • Vertex cut? • VPD needed, available in run 8? • Run 8 is low material, so no issue with Bremsstrahlung • Slightly preferable to prescale, • EMC design has projective geometry to z=0 • Better E resolution for single tower. • Caveat: normalization needs a mb trigger (prescaled) with identical vertex cut.

  15. Conclusions • Raising E threshold on high energy cluster. • f0=5.5 GeV, • rate goes to 12 Hz • Seff~6.5, Seff~42.7 in |y|<0.5 • Can get enough counts for pt spectrum? • More reduction is not desirable because impacts low pT. • cos(q)~-0.3 • Additional reduction possible (~10-20% rate reduction) • Impacts high-pT part. • Run 8  trigger can work with slightly tighter cuts.

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