BTeV Muon Trigger

1
BTeV Muon Trigger
Mats Selen Aug 25, 2003

• Algorithm
• Overview
• Efficiency Rejection
• Timing
• Results of running DSP based trigger code on a
  large sample of Monte Carlo events.
• RD
• What's Next.

2
Muon system has 3 stations with 4 views each
(R,U,V,S)
3
How to triggeron muon tracks
R2
R1
R0
m
In each octant For a given view (R,U,V, or
S) Examine correlations between hit tubes in
all 3 stations
4
Distance-To-Plane Cut
Muon tracks line on a simple plane R2 27.69 -
1.26R0 2.20R1(R0,R1,R2) in raw tube numbers

• muon tracks
• uds events

s1.5 tubes
good mevents
R2
R0
R1
Strategy Cut on closest distance to this plane
for each crossing/octant/view.
5

• m-
• m

Determiningtrack chargeis simple !
R2
R1
R0
R2
All we need to do is look at R2 vs R0.
R0
R2 1.275R0 -125
6
R2
Crude kinematicmeasurementsare also possible
Ptotal

• Not exploited further in this study.
• Can (for example) imagine calculating a
  crude dimuon mass.

R0
R2
Sin2q
R0
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Di-Muon Trigger
m
m-
Look for tracks by octant. Look for tracks in one
or more views (R,U,V or S). Tag each octant as
NO, POS or NEG A dimuon event has at least one
POS and one NEG octant
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Example Trigger Study

• Conditions for these plots
• Use all 384 tubes/view (also studied using
  only the outermost 352, 320 tubes)

2/4 and 3/4 means that 2 and 3 planes
respectively, out of the possible 4, were
needed to pass D-Cut toidentify a track in an
octant.
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D-cut 1
ltNgt 2
Dimuon Trigger Efficiency vs. Tube Hit
Efficiency(this example is for Cut 1)
There is a large parameter space that yields e gt
60 and Rej gt 500
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Performance vs. ltNgt (average number of min-bias
events/crossing)
3/4, e 97
Even for ltNgt 5 we can get a rejection of 500
with an efficiency of 60.
11
Size Speed

• Work done by UIUC ECE grad student John Cassel
• Ported RTES file-I/O code to the muon trigger.
• Implement clock-cycle counting technique for
  timing tests.
• Re-wrote optimized PC code for DSP (i.e. made
  it run fast !! )
• DSP results for efficiency rejection agree with
  PC!

TMS320C6711
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Executable Code91.3 kBytes
ltTimegt 760 ticks(6 ms _at_ 133 MHz)
ltTimegt 1686 ticks(13 ms _at_ 133 MHz)
Unless something changes,speed is not an issue.
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Muon Trigger Status

• Work to date is a existence proof.
• Trigger algorithm in good shape.
• Speed adequate.
• System will evolve as design continues

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BTeV Future

• You tell us!