CSC High Pileup Sumulations
Vadim Khotilovich
Alexei Safonov
Texas A&M University
June 15, 2009
Samples situation
• So far no news from Dave Newbold on progress
in centralized production of muon+new tracker
samples in FullSim
– Last time he wrote he was busy resolving isues with
FastSim
• If it might take too long, we might start
production of small CSC+tracker samples at
LPC CAF
– Need to know what exactly samples are needed first
– It would be good to pick up updated/fixed version of
LongBarrel
• Mike Weinberger mentioned last week that they were in
process of solving some issues with missing hits
• We plan on redoing tau+tracker samples soon as well as the
LB update will be ready
2009-06-15
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CSC Trigger Primitives Code
• Slava updated CSC L1 emulator code so that now CLCT
processing (and LCT) does not stop in first BX where a
CLCT was found
– More realistic implementation
– Important for high luminosities
– I have almost finished merging Slava’s update into my code
• Still ironing out small issues
• I was mostly busy with work on ME1/1:
– ME1a and ME1b separation
• ‘Naïve’ version works (ME1a and ME1b considered completely
separate chambers with “cheating” wire digis)
• Developing ‘smart’ separation algorithm
– Need to update efficiency studies with new code
– More on it next
2009-06-15
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ME1/1 Reminder
• In hardware
ME1/1
ME1/1 = ME1/a + ME1/b
h=1.55
– Continuous 1/a+1/b coverage
– 48 wire groups
– Some (#11-16) cross the border
• It complicates treating 1/a and 1/b as
separate logical chambers
ME1/b
• Wire groups
– ME1/a and 1/b have separate sets
– ME1/a: 48 strips
• ganged into sets of 3 in current HW
– ME1/b: 64 strips
2009-06-15
ME1/a
• Strips:
h=2.09
h=2.43
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ME1/1 Issues
• Crucial for Track Finder PT resolution
• Most affected at high luminosities
– The highest occupancies
• Especially in ME1/a
– Efficiency drops lower then in other chambers
• Bigger TMB FPGA is needed for algorithm
improvement
• Implementation of strips in ME1/a:
– Current “ganged strips” solution is not useful for
triggering
2009-06-15
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ME1/1 Action Plan
• Logically separate LCT finding in ME1/a and
ME1/b
– Un-ganging ME1/a in simulation
– Need to estimate A/CLCT occupancies per whole ME11
and its parts
• Do we need to increase maximum of 2 per ME11?
– Develop new algorithms for TMB
• Improving efficiency of
– CLCT finding
• Reduction of dead-time, taking advantage of bigger future FPGA
– TF track finding
• Investigation of existing high PU inefficiency (when ME1/a not
used)
– Waiting on Darin for plan; I can help
• Incorporation of ME1/a
2009-06-15
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Number of ALCTs per ME1/1
• Use PU400 minbias sample (no neutron BG!)
• Hack emulator code to print out number of ALCTs
with BX=6 before selecting the best two
• Estimate f(#ALCT>2) = N(#ALCT>2)/N(1≤#ALCT)
• Very clean exponential
distribution!
– Ni+1 = r Ni, r = 0.0605
• From geometric sequence
properties:
– f(#ALCT>2) = r2 = 0.37%
• The same number as from data!
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Number of ALCTs per ME1/1
• Our f(#ALCT>2) estimate was for minbias sample
• What would be f(#ALCT>2) for the case of chambers
crossed by a signal muon track in high pileup?
• We can estimate by adding +1 ALCT to chambers
– Results in “shifting” bins: 12, etc.
– Neglect small contribution of gamma rays from real muons
– Neglect nonlinear effects from overlapping signals from muon and
pileup
– As f(#ALCT>2) depends only on ratio of two neighboring bins
• f(#ALCT>2) = 0.37% should stay the same
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Number of CLCTs per ME1/1
• Complications:
– There are two separate parts: ME1/a and ME1/a
– emulator only finds the best and the second best CLCT
• No “before selecting the best two” number available
• Run two independent CLCT finders in ME1/a and ME1/b
– Each finds 2 max CLCTs (with deadtime artificially removed)
– For ME1/1 print sum of results from ME1/a and ME1/b
• Assume: distributions for CLCTs obey exponential law
– Need to consider that overflow i>2 bins are now added to N2
– Then r = N2/N1 becomes r = N2/(N1+N2) and still f(#CLCT>2) = r2
N1
N2
r
f(#CLCT>2)
ME1/a 14516 1219 0.077 0.60%
ME1/b 9671 587 0.057 0.33%
ME1/1
23268 2240 0.088 0.77%
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# A/CLCTs per ME1/1: Summary
• Estimated fraction of cases for PU400 when there are
more than two A/CLCTs with relation to the number of
cases when there are at least one A/CLCT:
– ALCTs: 0.4%
– CLCTs: 0.8%
• Can we consider those numbers sufficiently small?
– If so, we don’t really need to increase maximum of 2 per ME11
– One thing to take into account: occupancies in ME1/a are much
higher than in all other chambers
• E.g., comparing absolute values, what is 0.8% in ME11 could be 20%
or so in ME2/2
2009-06-15
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Towards better ME1/a and ME1/b
Separation
• ALCTs are reconstructed in whole
ME11
– They are angled at 29o
• Need to define how we assign an ALCT
to ME1/a or ME1/b
• Plots show halfstrip number (x) vs.
wire group number (y) for LCTs that
were matched to SimTrack
– Already from these plots can create
look-up tables
– More rigorous is to calculate from the
geometry
• Have it too
2009-06-15
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