1. SANE Cherenkov - Bigcal Efficiency Update
Whitney Armstrong

2. The Timing Fix 20ns bigcal Makes timing peak better
because it is now set
by the Cherenkov
cherenkov
50ns
50ns
15ns
bigcal
cherenkov
16ns
20ns

3. Before “Fixing Timing”
Understood - Cherenkov Channel 4 Bad HV Cable
Good lower mirror performance

4. After “fixing timing”
Note how both of these
areas have decreased

5. Parallel (after fix)

6. Bigcal Timing
Trigger groups are off set... sums of (sums of 64) are as well...
Were trigger signals corrected? ( time here for 80 channels? Which is about 30 ns...)

7. Observation
The Cherenkov mirror edges are not correlated with the inefficiency's vertical onset
Bigcal has large ~30ns timing difference between two sections
When Bigcal sets the time two peaks form in cherenkov TDC
Bigcal timing is correlated with the inefficiency onset
Bigcal timing is correlated with the energy dependence
Top of Protvino section (mirrors 5&6) gets worse after “timing fix”

8. Bigcal Time Difference
100 ns cherenkov gate
Single peak remains
because cherenkov
sets the time!

9. Cherenkov TDC - 72221 About 25-40ns difference between
Protvino and RCS
100ns

10. Cherenkov – 72221 (before fix)

11. Energy <1000
Ignore the top part that is missing... later...

12. Energy>1000

13. Energy <1000

14. Trajectory Based Cherenkov Performance
Require “OK” hit in Tracker AND Lucite w.r.t. seeding cluster
Look at Cherenkov efficiency with this criteria
Inefficiency should exist if Cherenkov mirror alignment is poor.

15. Trajectory based efficiency - Very Good

16. Run 72930 Improved efficiency on spherical mirrors due to
elimination of
background events
No energy cut

17. No energy cut

18. No energy cut

19. Note statistics
are poor until
here

22. Trajectory Based Cherenkov Performance Summary
With high energy cut (>1000 MeV) Cherenkov Efficiency improves (or stays the same)!!!
This contradicts the conclusion that the Cherenkov mirrors are not properly aligned.
Inefficiency should exist if Cherenkov mirror alignment is poor.

23. What is going on then?

24. A Possible Scenario Protvino RCS Cherenkov Higher energy events
Lower energy events time-walk their way into a better (efficient) trigger
Cherenkov time walks or has path length that takes it out of the trigger

25. Possible Scenario after fix High energy ~ fast. This section was timed
with cherenkov in the
middle of BC gate.
40ns maybe comes from:
A. Puckett's “BigCal Analysis Priimer”
40ns – RCS multiplexer 80ns – Prot multiplexer
25-40 ns
... Puckett goes on to say that timing groups are delayed to match
... if this is true for the signal used for the BETA trigger,
why would there be two peaks in the TDC spectra which did not set the time?!?

26. Before the Fix...
Note:
Protvino Earlier
RCS Later

27. Consistency thus far Questions:
Cannot explain early double peak unless unaligned Bigcal Timing groups were used for trigger
If unaligned groups were used with bigcal OR, this explains apparent bias toward low energy.
RCS arrives later which is better timed
Questions:
Was an unaligned Bigcal Timing group used with Cherenkov AND for the BETA trigger?
Bigcal Trigger was aligned... was BETA?

28. Bigcal T_trgbig is aligned!

29. Energy and Time Dependence
It is clear from the previous slides that the energy dependence is correlated with Bigcal Timing
Lower energies time-walk their way into a better trigger for Protvino.
Also, for larger phi angles, Cherenkov trigger arrives slightly later due to path length.

30. Conclusion
Energy dependence is not caused by Cherenkov mirror alignment
Bigcal timing needs to better understood.
Cherenkov efficiency quite good when combined with Forward Tracker and Lucite Hodoscope.

31. Backup Slides

33. Beta

34. Beta Vs Bigcal
20ns?

36. Energy Dependence Clusters with cherenkov TDC hit (loose) over all

37. Energy>1000 Notice how the top and bottom and curved.
Due to photon path length of Cherenkov
vertical displacement.