Particle Identification. N. Baltzell CLAS12 Ready for Science Review September 25, 2017

Transcription

1 Particle Identification N. Baltzell CLAS12 Ready for Science Review September 25,

2 Event Builder Overview The last CLAS12 service run, after all detectors reconstructions Retrieve event-based quantities, e.g. RF, heliticy, live-time Associate detector responses to create particles Forward Detectors, Central Detector, Forward Tagger Define event start time based on CLAS12 and RF Perform particle identification Provide all info in high level CLAS12 data banks 2

3 Creating Particles Charged particles: associate detector responses with tracks based on geometric matching Currently loose, flat detector-dependent cuts on DOCA between track and detector hit FTOF1B DOCA (cm) PCAL DOCA (cm) Identify trackless ECAL hits as neutrals, assume straight trajectory, and associate with other detectors unmatched hits based on geometric matching Matching quality (normalized distance) reported in output ForwardTagger and CentralDetector matching is already done in their dedicated recon services 3

4 Event Start Time Choose Trigger Particle Prefer highest energy electron, if one exists, requiring ECAL sampling fraction HTCC nphe FTOF response Else highest energy track with FTOF assumed a π else photons to be implemented Construct particle s vertex time and calibrated RF TDC signal to identify start time as nearest RF bunch time at vertex 4

5 Particle Identification (1) If HTCC nphe + ECAL Sampling Fraction à e+/e Else it s a hadron: Best hypothesis based on minimizing time difference between event start time t0 and vertex time ti = t0 tf T OF ECAL Energy After choosing event start time, identify other charged particles with a simple cut-based logic L, i = /K/p/d/... i (p) Momentum Possible overrides from Cerenkov e.g. kaon hypothesis gives best timing, but hit in LTCC and below kaon threshold à reassign to π PID χ2 reported in output (currently just as Δt) Planned to extend to more sophisticated scheme, e.g. likelihood Beta FTOF 1B Momentum 5

6 Particle Identification (2) Using test suite to check progress clas12-offline-software/ validation! test files automatically downloaded from webserver reconstructed & analyzed to perform data sanity checks yields, efficiency / misidentification 2-parJcle test events electron + another, in different sectors φ midesctor ± < θ < 35 e - : 1-9 GeV other : GeV Clas12FastMC at generator level to ensure trajectories intersect all detectors i.e. account for B-fields, acceptance also FT/CD events starting to be used Neutron / photon separation unfinished; currently based only on ECAL topology, timing-based separation to be implemented. Forward Detectors P I D (%) e 98 Truth e π K p γn π K p γn 98 A rough efficiency based on 1K events for each, averaged over given kinema:cs, used to help track EB so?ware development. For e / hadrons, demoninator requires a track; any other detector/reconstruc:on inefficiencies, kaon decay, etc, are absorbed. 6

7 Event Builder REC Bank Structures High level banks for analysis REC::Event! run/event #, helicity, event time, live time, faraday cup charge, etc REC::Particle REC:: ResponseType! e.g. Calorimeter, Scintillator, Cerenkov! contains index pointers to REC::Particle! lower-level detector banks REC::Trajectory, REC::TBCovMat, REC::VertDOCA, etc. 7

8 CCDB Most Event Builder parameters are already stored in CCDB, e.g. calorimeter sampling fractions position/time matching resolutions various cut values EB service loading them from CCDB, but not in full use yet; adoption in progress 8

9 Summary Event Builder framework status Trigger Particle / Start Time currently electron-focused, to be extended to π/ɣ Particle Identification currently simple cut-based algorithm with single PID FD algorithms developed and well-tested Forward Tagger incorporated, Central Detector partial Validation/testing suite in use checking yields, efficiencies/misidentification, data sanity checks CCDB structure and codes for Event Builder exists, adoption in progress Output bank structure defined and mostly populated Central Detector Import CD matching (already performed) into REC::Particle/Tracks/ Scintillator banks Apply timing-based hadron identification, and CVT-Veto for neutrals Read helicity into REC::Event Treat CD/FD overlaps Include ECAL timing for n/γ separation Incorporate RICH Extend cut-based PID scheme to likelihood/quality estimator Future Work Devs: Joseph Newton (ODU), Nathan, Raffaella Framework design by Gagik Gavalian 9