1. BTeV Muon Trigger Algorithm: Timing: R&D: Overview
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.
R&D:
What's Next.

2. Muon system has 3 stations with 4 views each (R,U,V,S)

3. How to trigger on muon tracks:
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 CutR2 R0 R1
Distance-To-Plane Cut
Muon tracks line on a simple plane:
R2 = *R *R1 (R0,R1,R2) in raw “tube numbers”
muon tracks
uds events
Distance to “plane”
s=1.5 tubes
good m events R2 R0 R1
Strategy: Cut on closest distance to this plane for each crossing/octant/view.

5. Determining track charge is simple !
All we need to do is look at R2 vs R0. R0
R2 = 1.275*R0 -125

6. Crude kinematic measurements are also possible:
Ptotal
Not exploited further in this study.
Can (for example) imagine calculating a crude dimuon mass. R0 R2
Sin2q R0

7. 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

8. 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” to identify a track in an octant.

9. D-cut = 1
<N> = 2
Dimuon Trigger Efficiency vs. Tube Hit Efficiency (this example is for Cut = 1)
There is a large parameter space that yields e > 60% and Rej > 500

10. Performance vs. <N>
(average number of min-bias events/crossing)
“3/4”, e = 97%
Even for <N> = 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

12. Executable Code: 91.3 kBytes
<Time> = 760 ticks (~6 133 MHz)
<Time> = 1686 ticks (~ MHz)
Unless something changes, speed is not an issue.

13. Muon Trigger Status Work to date is a “existence proof”.
Trigger algorithm in good shape.
Speed adequate.
System will evolve as design continues

14. BTeV Future
You tell us!