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

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

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

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

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

Inclusive Rates vs Energy Threshold in PCAL+ECAL Trigger Configuration Trigger Rate@0.5 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

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

Background Rates vs Energy Threshold in PCAL+ECAL Trigger Configuration Trigger Rate@0.5 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.

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.

Rates summary Even with a quite comprehensive cuts Background Inclusive Trigger Configuration Trigger Rate@0.5 GeV Threshold Energy Sum 100 kHz Energy sum + track 40 kHz Clusters in PCAL+ECAL 60 kHz Clusters + track 15 kHz Trigger Configuration Trigger Rate@0.5 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

Generator studies Inclusive generator with radiative corrections: code developed by S. Pisano based on work by M. Sargsyan, CLAS-NOTE 90-007 (1990). Background generator: 124000 electrons in 250 ns window on 5 cm target (provides luminosity of 1035) with electromagnetic, optical and hadronic processes.

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.

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.

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

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

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.

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.

Results, rates Trigger Configuration Trigger Rate@0.5 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 Rate@0.5 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

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.

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

backup NPE Inclusive Background