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Updates on LVL1 muon trigger rates at SLHC

Updates on LVL1 muon trigger rates at SLHC. Aleandro Nisati SLHC-ATLAS-Muon Meeting (25-01-07). Trigger rate. Study the prompt muon trigger rate (see next slide) Study the LVL-1 muon trigger accidental coincidences (barrel) assuming: To dispose of the finalized ATLAS shielding system

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Updates on LVL1 muon trigger rates at SLHC

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  1. Updates on LVL1 muon trigger rates at SLHC Aleandro Nisati SLHC-ATLAS-Muon Meeting (25-01-07)

  2. Trigger rate • Study the prompt muon trigger rate (see next slide) • Study the LVL-1 muon trigger accidental coincidences (barrel) assuming: • To dispose of the finalized ATLAS shielding system • A Be beam-pipe together with an improved shielding system capable of reducing the background fluences by a factor of 3 Background fluences are taken from the Radiation Task Force Book (January 03 layout)

  3. Trigger rates from proton rates are neglected (justified by past studies)

  4. Endcap trigger rate • The study is very similar to the one of the barrel, with the following differences: • The coincidence windows are typically smaller than those of the barrel • The low-pT trigger uses also the 3rd station: this provides an additional rate reduction • The time gate is slightly larger of the barrel one  Lower accidental trigger rate • Proton flux could be an important component of the trigger rate; more studies are needed to address this issue; here it is neglected. • The prompt muon rates at 20 GeV threshold is large because the weaker selection of low-pT muons (mainly from p/K decays): • Present, still preliminary, trigger rate for L=1035 cm-2 s-1: 89 kHz. • It goes to 44 kHz for 40 GeV/c threshold • Optimization work on going; wire-group/strip masking helps (but it could be not sufficient to reduce the rate)

  5. Dimuon triggers • The dimuon trigger is effective to select physics of interest at the cost of low selection rates • Detailed studies are on going in the “Muon Slice Trigger Group” • Probability for a single muon to generate a dimuon trigger (see next slide) • Some results, L= 1033 cm-2 s-1, threshold = 6 GeV/c pT : • Genuine 2muon events: 150 Hz • single.-mu double counted: 430 Hz • Cavern background induced 2mu negligible • Total 600 Hz • Extrapolation to higher pT threshold: • Assume a 2% probability to count single muons as dimuons  2.2KHz trigger rate • Dimuon triggers from physics: about 300 Hz

  6. Single muon double counting Based on recent results from Attila Krasznahorkay

  7. Dimuons from single muon pile-up • Uncorrelated dimuon trigger rate Tr2m= Tr21m• T • Tr1m = Tr m-prompt+ Tr m-fake • Tr2m = (Tr2m-prompt+ Tr2m-fake + 2 Trm-promptTrm-fake )T • T = bunch spacing = 50 ns (assumption); • Assume a fake muon rate (pT > 20 GeV/c) = 10 KHz(or 50 KHz, which is very pessimistic; proton trigger rate is neglected) • Consider the rate of single muons pT > 20 GeV (L=1035) = • 25KHz (prompt, barrel) • 89KHz (prompt, endcap) • 120KHz is the overall rate including cavern background triggers

  8. Dimuons from single muon pile-up • Expected dimuon rate is about 770 Hz (1.3 KHz if 50 KHz accidental rate is assumed) • 1m-1m pileup: 650 Hz (650 Hz) • 1m-1fake: 114 Hz (570 Hz) • 2fakes: 5 Hz (125 Hz)

  9. Single muon triggers - summary Dimuon triggers - summary • Barrel,20 GeV/c threshold, L=1035 cm-2 s-1 • “Prompt” muons, barrel 23.5 KHz • Cavern background 3.8 KHz • TOTAL ~ 30 KHz Full sys, 20 GeV/c threshold, L=1035 cm-2 s-1 • “Prompt” dimuons 0.3 KHz • Single mu double counted 2.2 KHz • Muon pile-up 0.8 KHz • TOTAL 3.3 KHz

  10. Possible Muon Trigger Menu • Use of single muon trigger and dimuon trigger in different rapidity regions and/or with different pT threshold: • Example • 1mu20 [barrel] OR 1mu40 [endcap] (if acceptable) • can we select on also on isolation?? • 2mu15 (or 2mu20) everywhere • Check the outcome in physics: see talk from S. Rosati to get an idea...

  11. Acknowledgments • This analysis is based on the detailed simulation results performed by the LVL1 Muon Trigger community (RPC, TGC, muCTPI): see talks given in the Trigger&Physics Weeks.

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