1. Nick Markov, UCONN Valery Kubarovsky, JLAB
CLAS12 Trigger Update
Nick Markov, UCONN
Valery Kubarovsky, JLAB

2. Outline Rate studies Studies of generators Results Future plans
Inclusive rate as a function of threshold in calorimeter and HTCC
Background rate as a function of threshold in calorimeter and HTCC
Studies of generators
Comparison of various distributions after trigger cut
Development of electron ID
Results
Future plans

3. 250 ns of CLAS12 Life@10^35 (GEMC)
2 GeV electron in a background

4. MC Generators Inclusive scattering generator Background generator
Verify and test the electron trigger configuration for exclusive scattering
Estimate the rate for exclusive scattering
Background generator
Estimate the trigger rate for different trigger configurations

5. Trigger Configurations
Energy sum
HTCC+PCAL+ECAL
HTCC: Nphe cut
Total energy sum(PCAL,ECAL)
Cluster Reconstruction
Reconstruction of clusters in PCAL and ECAL
Corrections on the light attenuation
Cut on the cluster energy sum(PCAL+ECAL)
Track reconstruction in DC
Test of the track reconstruction and the trigger rate

6. Inclusive Rates vs Energy Threshold in PCAL+ECAL
Trigger Configuration
Trigger GeV Threshold
Energy Sum
4 kHz
Energy sum + track
2.5 kHz
Clusters in
PCAL+ECAL
1.3 kHz
Cluster + track
1.2 kHZ
Rate is acceptable even for the simple energy sum trigger with threshold as low as 0.5 GeV

7. Inclusive Rates vs Number of Photoelectrons Cut in HTCC
Nphe
Rate is virtually independent on the number of photoelectrons up to Nphe ~ 20.

8. Background Rates vs Energy Threshold in PCAL+ECAL
Trigger Configuration
Trigger GeV Threshold
Energy Sum
100 kHz
Energy sum + track
40 kHz
Clusters in
PCAL+ECAL
60 kHz
Clusters + track
15 kHz
Simple energy sum trigger does not work, rate is 100 kHz.
With cluster and track rate is acceptable, but it is factor 12 higher than with inclusive generator.

9. Background Rates vs Number of Photoelectrons Cut in HTCC
Nphe
The rate dependence on the Nphe is such, that in order to suppress rate by a factor of 2 we need to go 20 Nphe.

10. Rates summary Even with a quite comprehensive cuts
Background
Inclusive
Trigger Configuration
Trigger GeV Threshold
Energy Sum
100 kHz
Energy sum + track
40 kHz
Clusters in
PCAL+ECAL
60 kHz
Clusters + track
15 kHz
Trigger Configuration
Trigger GeV Threshold
Energy Sum
4 kHz
Energy sum + track
2.5 kHz
Clusters in
PCAL+ECAL
1.3 kHz
Cluster + track
1.2 kHZ
Even with a quite comprehensive cuts
Ratebg ~ 12xRateinclusive

11. Generator studies
Inclusive generator with radiative corrections: code developed by S. Pisano based on work by M. Sargsyan, CLAS-NOTE (1990).
Background generator: electrons in 250 ns window on 5 cm target (provides luminosity of 1035) with electromagnetic, optical and hadronic processes.

12. Inclusive and background comparison
The question to answer: do we get the same from both generators?
Starting point: HTCC+EC+Track+Cluster θ
Inclusive
Expected: direct
proportionality
P, GeV
Nphe
Ring HTCC θ
Background
Npne
P, GeV
Ring HTCC
The answer is not entirely.

13. Generator studies Improve particle selection (electron ID):
Energy matching between track in DC and cluster in EC
Number of photoelectrons in HTCC
Vertex position of the track
Need to run cuts in parallel on both inclusive and background events.

14. Vertex of the track |X| < 2 cm |Y| < 2 cm |Z| < 2 cm
Inclusive X Y Z
Background X Y Z
Starting point: HTCC+EC+Track+Cluster

15. Energy match HTCC+EC+Track+Cluster + vertex cut (previous slide)
between track and cluster
E_cluster, GeV
E_cluster, GeV
E_cluster, GeV
Inclusive
same
cut
P_track, GeV
P_track, GeV
P_track, GeV
E_cluster, GeV
E_cluster, GeV
E_cluster, GeV
Background
P_track, GeV
P_track, GeV
P_track, GeV

16. Do we get the same now? The answer is Almost.
Starting point: HTCC+EC+Track+Cluster
Finish point: All cuts θ
Inclusive
P, GeV P
Nphe
Ring θ
Background
P, GeV
Nphe
Ring
The answer is Almost.

17. Timing Inclusive events Background events HTCC time, ns ECAL time, ns
PCAL time, ns
HTCC time, ns
ECAL time, ns
PCAL time, ns
250 ns
250 ns
250 ns
HTCC-ECAL time, ns
HTCC-PCAL time, ns
ECAL-PCAL time, ns
HTCC-ECAL time, ns
HTCC-PCAL time, ns
ECAL-PCAL time, ns
Black - Energy Sum, red – all cuts
Inclusive and background timing looks reasonable;
Time difference between different detectors is similar
between inclusive and background events;
Background distribution has no tails, so it will not help us with rate;
No cluster timing yet – opportunity to improve selection in the future.

18. Results, rates
Trigger Configuration
Trigger GeV Threshold
Energy Sum
4 kHz
Energy sum + track
2.5 kHz
Clusters in
PCAL+ECAL
1.3 kHz
Cluster + track
1.2 kHz
All cuts
750 Hz
Trigger Configuration
Trigger GeV Threshold
Energy Sum
100 kHz
Energy sum + track
60 kHz
Clusters in
PCAL+ECAL
40 kHz
Clusters + track
15 kHz
All cuts
9 kHz
Background rate is suppressed by a factor of 2, but ratio of background/inclusive is roughly the same

19. Results, summary
With a simple Energy Sum trigger rates of inclusive and background events are different by a factor of ~ 12;
Simple Energy Sum trigger does not select electron well enough;
Sophisticated electron ID matches background and inclusive distributions better;
Rates are still off by a factor of ~12.

20. Next steps Understand the nature of discrepancy Estimate rates
Determine trigger cut parameters
Understand the effect of trigger cuts on other reactions (DVCS, SIDIS)
HTCC
CED by David Heddle

22. backup NPE
Inclusive
Background