CLAS Collaboration Meeting 18-21 June, 2019 A Charged Particle Veto in the Central Detector Using Only CND and CTOF Katheryne Price, IPN Orsay for the CLAS Collaboration 20/06/2019 Overview Background and Motivation Development and Evolution Results Implementation Further Ideas and Considerations Charged Particle Veto for the CD Using CND & CTOF 2 Background Central Neutron Detector
Plastic scintillator 3 radial layers, total ~10 cm Angular coverage 40 < <120 Azimuthal coverage 2 Neutron detection efficiency ~10% Central Time-of-Flight Detector Plastic scintillator ~3 cm thick Angular coverage 35 < <125 Azimuthal coverage 2 Potential neutron detection efficiency ~3% Charged Particle Veto for the CD Using CND & CTOF 3 Motivation Tracking in the CVT is neither 100% efficient nor uniform CND sees charged particle contamination Can an effective charged particle veto be constructed using only CTOF and CND? (spoiler: yes!)
Charged Particle Veto for the CD Using CND & CTOF 4 Development and Evolution Requirements: Veto charged particles without losing neutrons May only use position and energy deposition information from CTOF and CND Cannot rely on vertex tracking ROOT macro TSelector CND clustering COATJAVA (EventBuilder) Start with what we observed in single-particle, singlemomentum simulations Neutrons at 400-1000 MeV Protons from 400-1000 MeV* + from 400-1000 MeV*
Charged Particle Veto for the CD Using CND & CTOF 5 *RG-A shows we wont see many above 800 MeV Development and Evolution We tried many different criteria... Charged Particle Veto for the CD Using CND & CTOF 6 Development and Evolution Interesting trials Sector/ Criteria: Charged particles have curved tracks if changes more than (5, 10, &c.) degrees or (1, 2) sectors, apply veto Problem: Particles frequently graze multiple sectors,
making this a fuzzy and unreliable cut Layer ordering Criteria: If hits within an event trigger layers in order radially, apply veto Problem: In real life, we wont know which hit was first Charged Particle Veto for the CD Using CND & CTOF 7 Development and Evolution Milestone trials Hit and layer multiplicities defined Allow for a cut to be made based on how many hits within an event, or how many layers were triggered (regardless of number of hits)
Total event energy deposition defined Allow for a cut to be made based on the total energy deposition of an event Also defined total event energy per detector (very useful in conjunction with hit/layer multiplicity cuts) Charged Particle Veto for the CD Using CND & CTOF 8 Development and Evolution The veto today Two main sections Section 1 defines useful quantities (total event energy, hit and layer multiplicity) for(int i=0; i1) {
counts++; if(CND_hits_layer[i]==1) { counts_l1++; } [...] } } for(int i=0; i1) { ctof_counts++; } } if(counts>0 && ctof_counts==0) { for(int i=0; i1) { total_event_energy += CND_hits_energy[i]; total_cnd_energy += CND_hits_energy[i];
cnd_only_counts++; } } } Charged Particle Veto for the CD Using CND & CTOF 9 Development and Evolution The veto today Section 2 applies the veto using the quantities defined in section 1 an example: else if(cnd_only_counts>0) { if(total_cnd_energy>10 && counts<3) { neutron++; cnd_only_neutron_counts++; } if(total_cnd_energy<=10 && counts<4) { neutron++;
cnd_only_neutron_counts++; } } Charged Particle Veto for the CD Using CND & CTOF 10 Events only in CND CND total event energy > 10 MeV, and hit multiplicity less than 3 Increment two counters neutrons and CND only neutrons Development and Evolution The veto today 600 MeV +
600 MeV neutrons 600 MeV protons If an event was in CTOF only: total energy for the event is < 13 MeV and hit multiplicity is < 3 If an event was in CND and CTOF: CND event energy is < 30 MeV, and CTOF event energy is < 13 MeV, and layer multiplicity is exactly 1 MeV MeV Charged Particle Veto for the CD Using CND & CTOF
total event energy is < 10 MeV, and CTOF event energy is < 10 MeV, and layer multiplicity is exactly 2 If an event was in CND only: total event energy > 10 MeV and hit multiplicity is < 3 11 Total event energy 10 MeV and hit multiplicity is < 4 Results Baseline ~44% of 400 MeV protons detected in CND were ~80% of neutrons detected in CND were detected detected only in CND; <1% of higher momentum in CND were detected in Very few pions of only all momenta protons
~55% of neutrons detected overall were detected only CND But only 0.5% of 400 MeV protons detected in only in CND CND overall All files: 100,000 particles =0 = 60 Charged Particle Veto for the CD Using CND & CTOF ~60% of neutrons detected in CTOF were because almost all of them stop in CTOF. detected only in CTOF A very small or percentage only in CTOF of protons otherwise ~28% of neutrons detected overall were were detected only in CTOF detected only in CND
12 Above 400 MeV, Only about 15% of almost almost all all protons were detected neutrons detected detected in both were CND were detected in detected andinCTOF both CND both CND and CTOF and CTOF CND
+ CTOF + CND&CTOF Results 400 MeV neutrons protons + MeV n p + Charged Particle Veto for the CD Using CND & CTOF 13 Results
600 MeV neutrons protons + MeV n p + Charged Particle Veto for the CD Using CND & CTOF 14 Further Testing Further testing is underway to ensure that the veto is suitable for use in reconstruction of real data: Testing on Monte Carlo simulations of particles at all appropriate angles and momenta
Inclusion of kaons Tests on already-reconstructed RG-B data Charged Particle Veto for the CD Using CND & CTOF 15 Implementation Implementation will go in parallel with optimization and testing we dont anticipate any changes to the structure of the veto, likely just energy and multiplicity refinements to the already-defined criteria! Charged Particle Veto for the CD Using CND & CTOF 16 Implementation
Tentative plan (as of yesterday): At the beginning of the CLUSTERING for CND and CTOF, the following quantities must be defined, if not present already, for hits that qualify to be in the same cluster: Total energy Hit multiplicity, including the proper edep threshold Layer multiplicity, including the proper edep threshold Then the clustering should be done (needs to be checked and maybe optimized), and the above quantities, on which the veto is based upon, should be passed to EventBuilder. In EventBuilder: for CD neutral candidates, i.e. hits in CND and/or CTOF, which are NOT matched to CVT tracks (but it can be done also for those that are): Distinguish between the three cases: CTOF only, CND only, CTOF+CND For each case, create a neutral flag, based upon the veto criteria For events for which the neutral flag is on, proceed to neutron PID check: low and high b AND edep cut (right now only high b cut is present for CND) Include also PID for neutrons in CTOF (not present yet) Other ideas/plans: Study additional veto criteria for photons, on top of beta/edep cut Include PID for photons in EB, not present yet (just reverse neutron cut) ID of pions and protons (with rough momentum/angle reconstruction) Charged Particle Veto for the CD Using CND & CTOF 17 Summary
Refining and testing of a CTOF/CND-only charged particle veto is underway At present, the veto has been tested on single-particle, single momentum simulations* Implementation into the CND clustering algorithm will go in parallel with further testing
