UCLA meeting, 2012 Hauser 1
Reviews galore• Yesterday: GEM proposal review (more later)• Mon-Tues Feb 25&26: Workshop #2 on CSC
Planning for LS1• Created agenda at https://indico.cern.ch/conferenceDisplay.py?confId=236792
• Weds-Thurs Feb 27&28: CERN review of ME1/1 and ME4/2 projects• Agenda for first day at https://
indico.cern.ch/conferenceDisplay.py?confId=235558• Agenda for 2nd day under development (Loveless)
• Meanwhile: ARC review for Z+jets at 7 TeV
UCLA meeting, 2012 Hauser 2
GEM review: motivation• From 2 weeks ago
• Lever arm in 1/1 station increased 2.5-5.0x• Resolution allowed by current 16:1 ganging for trigger is
~8 mrad, need at least 4x finer (see below) for trigger
Df(CSC-GEM)~ 3 mradDx ~6 mm
pT=20 GeV
pT=5 GeV
Full Geant Simulation
• Muon momentum from stub positions
• DfXY=f(ME-X)-f(ME-Y)
• Measurement driven by Df12
• ME-1/1 defines the accuracy
• Least scattering and B field
• “Flattening”: mismeasured soft muons
• Soft muons scattering in the absorber can occasionally have stubs align like for a high pt muon
• Rare but there are lots of them!
• Tails in L1 momentum resolution
• A fundamental issue with no solution
• At some point you just hit the wall• Likely the last improvement, as the
new TF has likely reached that wall
FORWARD TRIGGER RATE
New CSCTF: rate reduction factor
CMS DAQ TDR
POTENTIAL SOLUTIONS• Removing tails in L1 muon momentum resolution
to control trigger rate cannot be done without a second detector:
• Match to inner tracker tracks at L1
• Great but unavailable until LS3
• Can a second muon system improve momentum resolution?
• It could if we can measure and use the “bending angle”
• Used in the Barrel; CSCs are too thin to see the bend on its own
• A new detector in YE-1/1 (the least affected by scattering and largest magnetic field)
• Increase “lever arm” & have enough spatial resolution to measure bending angle
• Physical constraints allow a maximum lever arm of Dz=30-50 cm in YE-1/1
• The new detector needs ~2-3 mm or better trigger resolution to effectively discriminate 5-10 GeV muons from 20+ GeV ones
YE-1/1 pT=5 GeV pT=20 GeVDxDz=30 cm 3±1mm 12±3mm
View from the top of CMS down
BENDING ANGLE: SIMULATION
• GEM-CSC bending angle measurement using GEANT simulation:
• Muons with PT=5 and PT=20 GeV
• Digi level (full GEM granularity) – this is what HLT Level-2 can do
• Slight deterioration due to discretization and resolution effects, but still strong discrimination
Df(CSC-GEM)~ 4 mradDx ~8 mm
pT=20 GeVpT=5 GeV
“Close” chamber pairs “Far” chamber pairs
• Extremely preliminary • Accounts for some but not all CSC TF
improvements
• An explicit cut on the CSC-GEM bending angle to be ~100% efficient at and above 20 GeV
• In real case we will send “bending angle pattern”
• Dramatic decrease in ratio towards low pt due to that cut
• Ratio will flatten once bending patterns for pT ranges are defined
• The plot is less than 24 hours old, so take it as a promise that the final plot is on the way
EFFECT ON THE TRIGGER RATE
Super Preliminary
Super Preliminary
UCLA meeting, 2012 Hauser 7
Implementation• Use 4 of 5 unused fibers in ME1/1 bundle of 12
• Feeds directly into TMB• GEM group proposed to put 2 chambers in place during LS1
• Front-end electronics not final• Trigger 4-16x worse segmentation than final electronics• Readout system cobbled together• DAQ electronics effort thin
• New suggestion:• Put a “slice test” with 3, 6, or 9 GEM chambers in during long YETS
between 2016-2017 (when new pixels installed).• Could use final electronics• (Time to develop good TMB firmware)• Transparencies for front end at
https://www.dropbox.com/s/6hfyzy935sr0jy1/Aspell_LS2_Electronics.pdf and FPGA/DAQ at https://www.dropbox.com/s/sftbtist9oxgky8/Gilles_2013-02-GEM-Review.pdf