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Using the HBD for a High-pT Charged Pion Trigger in p+p Collisions at PHENIX

Explore using the HBD for triggering charged pions with pT>5 GeV/c in p+p collisions, enhancing detection efficiency. Investigate challenges, pad assignments, and cluster charge distributions.

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Using the HBD for a High-pT Charged Pion Trigger in p+p Collisions at PHENIX

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  1. Using the HBD for a High-pT Charged Pion Trigger in p+p Collisions at PHENIX Dave Kawall Christine Aidala UMass Amherst

  2. Motivation and Basic Concept • Currently no lvl1 charged trigger in the central arms • Offline charged analyses only obtain ~30% of pi0’s found in same data set • Trigger for charged pions with pT>~5 GeV/c could be formed using coincidences between the HBD and RICH • Take advantage of current RICH trigger implementation in ERT • Current RICH-EMCal coincidence for the electron trigger requires shower in EMCal  PbSc only 0.85 interaction length • Recover charged pions that only produce MIP in EMCal by using HBD instead

  3. HBD pads fired per event (PYTHIA MB) In p+p simulation, see on average less than 1 pad firing per event. counts counts # HBD pads fired per event # HBD pads per cluster

  4. HBD Pad Charge—Max per Event (PYTHIA MB) counts Sample HBD-only rejection factors for various charge thresholds per pad 1.0 fC -> RF = 3.73.0 fC -> RF = 5.35.0 fC -> RF = 7.17.0 fC -> RF = 9.19.0 fC -> RF = 11.3 charge (fC) N.B. Gain in simulation is 1x104. Observed gains ~5x103. Question for HBD group: Does charge distribution in MB look reasonable? (ignoring “known” factor 2) (1 fC ~ 2/3 photoelectron)

  5. Cluster Charge vs. Simulated pT(single particle simulation) Cluster charge (fC) Does cluster charge for particles below threshold (MIPs) look reasonable? pT (GeV/c)

  6. Will Scintillation Be a Problem? • What is scintillation yield per charged particle in wavelength range of CsI sensitivity? • Working assumption: Scintillation not an issue in p+p because so few charged tracks; 1 photon per pad max. • Do low-energy particles ever spiral around forever? • (++ magnetic field config in p+p)

  7. Efficiencies vs. pT (single particle simulation) Turn-on dominated by RICH, which has higher threshold than HBD. Efficiency HBD only Efficiency plateaus at or just above ~6 GeV/c. ~50% efficiency from simulation. (~75% HBD x ~65% RICH) Efficiency RICH only 6 GeV/c 75% HBD efficiency reasonable? Where are losses in simulation primarily coming from? Could we gain efficiency by running with RB off in pp? 0.5 Efficiency HBD and RICH pT

  8. How are the pads assigned to the FEMs? • Perhaps the simplest level-1 output from the HBD would be the OR of 48 pads in a FEM - then check to see if RICH hit at same phi • How are the pads assigned to a FEM? (in strips? rectangles?) - ideally we’d like to map RICH elements with HBD elements at the same phi - this would be easier if FEMs mostly contain pads at same or similar phi

  9. Extra slides

  10. HBD Cluster Charge (PYTHIA MB)

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