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Effects of Endcap Staging/Descoping. D.Acosta University of Florida. Effects of Endcap Staging/Descoping. Staged Muon scenarios: No ME 4/2 (CSC) No fourth CSC station for  < 1.8 No RPC for stations 2,3,4 No endcap RPC trigger, but station 1 there to cancel CSC ghosts if needed

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effects of endcap staging descoping

Effects of Endcap Staging/Descoping


University of Florida

effects of endcap staging descoping1
Effects of Endcap Staging/Descoping
  • Staged Muon scenarios:
    • No ME 4/2 (CSC)
      • No fourth CSC station for  < 1.8
    • No RPC for stations 2,3,4
      • No endcap RPC trigger, but station 1 there to cancel CSC ghosts if needed
    • ME1/1 strips put into “OR”
      • Reduce channel cost by not segmenting ME1/1 in 

Darin Acosta

me4 2 staging
ME4/2 Staging
  • With RPC trigger in place, CSC trigger runs in “loose” mode for high efficiency:
    • Only 2 CSC stations are required: one must be ME1 and one must be ME2 or ME3 (relax ME1 condition for DT/CSC overlap)
    • In principle, ME4 cannot affect efficiency or rate by design
    • But PT assignment is slightly better for 3-station tracks than for 2-station tracks, so might expect some changes to CSC rate and efficiency above certain PT threshold without ME4
    • GMT requires match between CSC and RPC for low quality CSC muons, and optimizes the PT assignment, so any effect is reduced after GMT
  • Without RPC trigger in place, the CSC trigger must run in “tight” mode for improved rate reduction
    • Three CSC stations are required, including ME1
    • No redundancy without ME4 means efficiency loss

Darin Acosta

me4 2 staging efficiency
ME4/2 Staging – Efficiency


Single muons: 3< PT<100 GeV

“loose” (unchanged)  = 97%

ME4/1 in/out

“tight” ME4/2 in, =79%

“tight”, ME4/2 out,  =73%


Darin Acosta

me4 2 staging rates
ME4/2 Staging – Rates

L=21033  5X


CSC loose, no ME4/2


CSC loose

CSC loose, no ME4/2

CSC tight

CSC loose

GMT is


CSC tight without RPC achieves about same rate as CSC loose with RPC in GMT

Darin Acosta

me4 1 needed at high eta
ME4/1 Needed at High Eta



  • GMT as in ORCA 5.1.2
    • rate at 20 GeV/c: 3.1 kHz
    • L1 efficiency(*): 96.6 %
  • re-tuned GMT selection:
    • Only three-station CSC tracks used without RPC confirmation
    • rate at 20 GeV/c: 1.4 kHz
    • L1 efficiency(*): 96.3 %
  • (*)efficiency to find muon of any pT in flat pT sample

ORCA 5.1.2

Rate from unconfirmed 2-station CSC tracks, since no RPC coverage

GMT single muon trigger rates (pT > 16 GeV/c)

re-tuned GMT


Darin Acosta

mixed mode csc trigger
Mixed Mode CSC Trigger
  • Without RPC trigger and without ME 4/2, still allow “loose” CSC trigger for 1.2 <  < 1.8 (but “tight” everywhere else)
  • Gains efficiency here
  • Still want ME 4/1 at high 
  • DT/CSC overlap still a problem


 ~ 85%


Rate from “mixed-mode”close to that from “tight”

Darin Acosta

me1 1 staging
ME1/1 Staging
  • Recall that ME1/1 has split strips
    • Motivation was to reduce occupancy
    • Can we avoid it to reduce channel cost?
  • From muon TDR:
    • Charged particle occupancies in either half of ME1/1 are about 0.5%per chamber per BX
    • Neutron hit occupancies are no more than about 2%, but as they are uncorrelated through the chamber, a much smaller fraction actually give trigger primitives.
      • So these numbers are not large, and in fact are smaller by about 50% than the numbers for the other CSC chambers (ME2/1, ME3/1, and especially ME4/1)
      • In principle there should not be any problem if we can OR the strips from top to bottom of ME1/1

High Lumi: L=1034

Darin Acosta

csc lct rates in orca5
CSC LCT Rates in ORCA5


High Lumi: L=1034

min bias pile-up only

no neutrons

ME 1/1: 7 MHz

ME 1/A: 10 MHz

For 72 chambers of each type, occupancy per BX is:

ME 1/A: 0.35%

ME 1/1: 0.24%

Darin Acosta

csc lct occupancy with neutrons
CSC LCT Occupancy with Neutrons
  • Similar study performed with min bias pile-up and neutrons at L = 1034 using ORCA5
  • Chamber LCT occupancies:

Anode+Cathode Cathode only

    • ME 1/A: 0.46% ME 1/A: 0.61%
    • ME 1/1: 0.44% ME 1/1: 1.50%
    • ME 1/2: 0.05% ME 1/2: 0.10%
    • ME 1/3: 0.05% ME 1/3: 0.14%
    • ME 2/1: 0.29%
    • ME 2/2: 0.34%
    • ME 3/1: 0.21%
    • ME 3/2: 0.25%
    • ME 4/1: 0.25% ME 4/1: 0.81%
    • ME 4/2: 0.86% ME 4/2: 2.54%


Darin Acosta

discussion of me 1 1 strip or
Discussion of ME 1/1 Strip “OR”
  • Combining the two halves of ME 1/1 can’t increase the trigger rate if the track segments come from real muons (i.e. correlated hits)
  • Extra trigger rate can only come from random combinations forming ghost track segments, which in turn form additional triggers
  • If the current LCT occupancies are dominated by real correlated hits, expect ME 1/1 and ME 1/A occupancies to add
  • If neutron-induced random hits dominate, expect occupancy to scale non-linearly
    • “Guestimate”: order of magnitude increase
  • How to tell without detailed simulation of strip OR?
  • Study dependence of occupancy with background level
  • ORCA4 study with pile-up and neutrons: Occupancy for L = 1034 L = 31034ME 1/A: 0.3% 0.9%ME 1/1: 0.3% 0.9%
  • Therefore, occupancies scale linearly

Darin Acosta

  • ME 4/2 staging
    • With RPC: No change in GMT rate or efficiency
    • Without RPC: Approximately no change in rate requiring 3 CSC stations, but 25% acceptance loss in endcaps for “tight” trigger (12% loss for mixed-mode trigger)
    • In any case, ME 4/1 is useful to reduce rate by factor of two if efficient triggering at >2.1 is desired
  • ME 1/1 Staging
    • At high luminosity, the ME 1/1 and ME 1/A track segment occupancies are about 0.5 – 1.0% per BX
    • Combining the two, the occupancies add and would be of order 1–2%
    • At low luminosity, occupancies would be 5X lower
    • Therefore, expect no change in efficiency or rate if strips in ME 1/1 and ME 1/A are put into an “OR”
    • Exactly how to do this is up to chamber designers
      • Different strip pitch in ME 1/1 and ME 1/A in current simulation
    • Perhaps it could be possible to segment HV so that high  wires can be turned off if occupancies turn out to be higher than expected (as is possible in other CSC chambers)
      • Complicated by wire tilt, however

Darin Acosta