Effects of Endcap Staging/Descoping
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Transcript of Effects of Endcap Staging/Descoping
Effects of Endcap Staging/DescopingEffects of Endcap Staging/Descoping
D.AcostaUniversity of Florida
CMS Week, September 2001
Darin Acosta2
Effects of Endcap Staging/DescopingEffects of Endcap Staging/DescopingStaged Muon scenarios:
1. No ME 4/2 (CSC) No fourth CSC station for < 1.8
2. No RPC for stations 2,3,4 No endcap RPC trigger, but station 1 there to cancel CSC
ghosts if needed3. ME1/1 strips put into “OR”
Reduce channel cost by not segmenting ME1/1 in
CMS Week, September 2001
Darin Acosta3
ME4/2 StagingME4/2 StagingWith 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
CMS Week, September 2001
Darin Acosta4
B.Scurlock
ME4/2 Staging ME4/2 Staging – Efficiency– Efficiency
“tight”, ME4/2 out, =73%
“tight” ME4/2 in, =79%
“loose” (unchanged) = 97%
ME4/1 in/out
Single muons: 3< PT<100 GeV
CMS Week, September 2001
Darin Acosta5
ME4/2 Staging ME4/2 Staging – Rates– Rates
GMT isunchanged
CSC loose
CSC loose, no ME4/2
U.Gasparini
L=21033 5X
CSC loose, no ME4/2
CSC loose
CSC tight
L=1034
CSC tight without RPC achieves about same rate as CSC loose with RPC in GMT
CMS Week, September 2001
Darin Acosta6
ME4/1 Needed at High EtaME4/1 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
Rate from unconfirmed 2-station CSC tracks, since no RPC coverage
GM
T s
ing
le m
uo
n t
rig
ger
rat
es (
pT >
16
GeV
/c) ORCA 5.1.2
re-tuned GMT
H.SakulinL=21033
CMS Week, September 2001
Darin Acosta7
Mixed Mode CSC TriggerMixed 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
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Rate from “mixed-mode”close to that from “tight”
~ 85% L=1034 loose
CMS Week, September 2001
Darin Acosta8
ME1/1 StagingME1/1 StagingRecall 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
CMS Week, September 2001
Darin Acosta9
CSC LCT Rates in ORCA5CSC LCT Rates in ORCA5J.Mumford
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%
CMS Week, September 2001
Darin Acosta10
CSC LCT Occupancy with NeutronsCSC 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%
B.Scurlock
CMS Week, September 2001
Darin Acosta11
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 = 31034
ME 1/A: 0.3% 0.9%ME 1/1: 0.3% 0.9%
Therefore, occupancies scale linearly
CMS Week, September 2001
Darin Acosta12
SummarySummaryME 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