SANE Cherenkov - Bigcal Efficiency Update Whitney Armstrong

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 https://hallcweb.jlab.org/hclog/0902_archive/090212125207.html

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

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

Parallel (after fix)

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...)

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”

Bigcal Time Difference 100 ns cherenkov gate Single peak remains because cherenkov sets the time! https://hallcweb.jlab.org/hclog/0902_archive/090212125207.html

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

Cherenkov – 72221 (before fix)

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

Energy>1000

Energy <1000

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.

Trajectory based efficiency - Very Good

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

No energy cut

No energy cut

Note statistics are poor until here

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.

What is going on then?

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

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?!?

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

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?

Bigcal T_trgbig is aligned!

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.

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.

Backup Slides

Beta

Beta Vs Bigcal 20ns?

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

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