Effects of Endcap Staging/Descoping
D.Acosta
University of Florida
Effects of Endcap Staging/Descoping
Staged Muon scenarios:
1.
2.
3.
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 
CMS Week, September 2001
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Darin Acosta
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

CMS Week, September 2001
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Darin Acosta
ME4/2 Staging – Efficiency
B.Scurlock
“loose” (unchanged)  = 97%
Single muons:
3< PT<100 GeV
ME4/1 in/out
“tight” ME4/2 in, =79%
“tight”, ME4/2 out,  =73%

CMS Week, September 2001
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Darin Acosta
ME4/2 Staging – Rates
L=21033
5X

L=1034
CSC loose, no ME4/2
U.Gasparini
CSC loose
CSC loose, no ME4/2
CSC tight
CSC loose
GMT is
unchanged
CMS Week, September 2001
CSC tight without RPC
achieves about same rate as
CSC loose with RPC in GMT
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Darin Acosta
GMT single muon trigger rates (pT > 16 GeV/c)
ME4/1 Needed at High Eta
ORCA 5.1.2
L=21033
H.Sakulin
GMT as in ORCA 5.1.2

rate at 20 GeV/c: 3.1 kHz

L1 efficiency(*): 96.6 %
Rate from unconfirmed
2-station CSC tracks,
since no RPC coverage
re-tuned GMT selection:
re-tuned
GMT

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

CMS Week, September 2001
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Darin Acosta
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)

loose
 ~ 85%
L=1034
Title:
(Lands cape A 4)
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Gains efficiency here
 Still want ME 4/1 at high 
 DT/CSC overlap still a problem

CMS Week, September 2001
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Rate from “mixed-mode”
close to that from “tight”
Darin Acosta
ME1/1 Staging
Recall that ME1/1 has split strips
High Lumi: L=1034
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
CMS Week, September 2001
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Darin Acosta
CSC LCT Rates in ORCA5
J.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
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Darin Acosta
CSC LCT Occupancy with Neutrons
B.Scurlock
Similar study performed with min bias pile-up and
neutrons at L = 1034 using ORCA5
Chamber LCT occupancies:
Anode+Cathode
 ME 1/A: 0.46%
 ME 1/1: 0.44%
 ME 1/2: 0.05%
 ME 1/3: 0.05%
 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 4/2: 0.86%
CMS Week, September 2001
Cathode only
ME 1/A: 0.61%
ME 1/1: 1.50%
ME 1/2: 0.10%
ME 1/3: 0.14%
ME 4/1: 0.81%
ME 4/2: 2.54%
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Darin Acosta
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1034
ME 1/A: 0.3%
0.9%
ME 1/1: 0.3%
0.9%
 Therefore, occupancies scale linearly

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Darin Acosta
Summary
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
CMS Week, September 2001
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Darin Acosta