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

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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