1. Simulation/Reconstruction for CPP Experiment David Lawrence JLab Sept. 27, 2013 9/27/131simulation status - D. Lawrence - JLab

2. The GlueX Detector in Hall-D 29/27/13 CPP Experiment will use GlueX detector in Hall-D: Linearly polarized photon source (~9GeV for GlueX) 2T solenoidal magnetic field (  p/p = few %) Drift chambers High resolution Time-of-flight detector FCAL segmented lead-glass calorimeter Modifications to standard GlueX setup: Replace LH2 target with thin Sn target Move target upstream to improve low-angle acceptance Remove start-counter Add muon/pion detector Move coherent peak to 6GeV simulation status - D. Lawrence - JLab

3. Experimental Setup FDC Solenoid TOF FCAL Target Signal reaction Beam polarization All occur via the Primakoff effect (interaction with the Coulomb field of nucleus) All result in very forward going particles Low t (-t < 0.005 GeV 2 ) 9/27/133simulation status - D. Lawrence - JLab Muon Detector Normalization

4. Motivation for geometery changes in target region With start counterWithout start counter 9/27/134simulation status - D. Lawrence - JLab Smaller z values = target is further upstream GlueX LH2 target extends from z=50cm to z=80cm

5. Start Counter is in the way 9/27/135 Location: (X, Y, Z) = (2.3, 0, 96.6) =============================================== Volume: STRC material: Scintillator density: 1.032 g/cm^3 rad. length: 42.1442 cm A: 11.0618 Z: 5.56867 ancestory: STRC -> STRT -> LASS -> HALL -> SITE Nose angle=17.5 o Trajectory=1.4 o Material=3mm/sin(18.9 o ) = 9.3mm or 0.022 rad. lengths simulation status - D. Lawrence - JLab

6. GlueX Simulation Tool Chain Generators (pythia, genr8, …) Generators (pythia, genr8, …) hdgeant (hddsGeant3.F) hdgeant (hddsGeant3.F) mcsmear hdgeant.hddm hdgeant_smeared.hddm generated.hddm reconstruction Multiple generators exist including: bggen (pythia + low energy reactions) genr8 (isobar t-channel configurable) coherent bremstrahlung photons GEANT3-based simulation engine: detailed geometry defined partial hit digitization Final stage smearing: cumulative-level smearing done dark hits/noise hits added future: dead-channel removal HDDS XML CentralDC_HDDS.xml ForwardTOF_HDDS.xml … Simulation geometry defined in XML 9/27/136simulation status - D. Lawrence - JLab

7. 9/27/137simulation status - D. Lawrence - JLab

8. 9/27/138 Without Vertex Constraint simulation status - D. Lawrence - JLab

9. With Vertex Constraint 9/27/139simulation status - D. Lawrence - JLab

10. Kinematics of Experiment 9/27/1310    is angle between  scattering plane and polarization vector in helicity frame    is angle between  system and incident photon polarization vector in CM frame simulation status - D. Lawrence - JLab

11. Primakoff +  o Primakoff only W  (GeV/c 2 ) Linear Polarization of incident photon beam helps distinguish Primakoff from coherent  o production 9/27/1311     (invariant mass of     system) simulation status - D. Lawrence - JLab

12. Extracting the Cross Section (sort of) 9/27/13simulation status - D. Lawrence - JLab12 Generated (not simulated) events representing 10 days of running with 70% polarization and  background only Fits done for different W bins to extract Primakoff and coherent  contributions Black: MARK-II data Red: Statistical errors (from fits) Curves: Theory

13. Beam Polarization via  o Primakoff 9/27/13simulation status - D. Lawrence - JLab13   Use asymmetry between vertical and horizontal polarization data to extract polarization Plots by Alexander Mushkarenkov Exercise done with 100% polarization and no backgrounds

14. Software Level-1 Event filter A. Somov GlueX-doc-1043 Event is kept if either L1a_fired or L1b_fired is true Roughly 50% of hadronic events should be accepted by L1 trigger Some tuning of FCAL cut will be needed Trigger implemented in TRIGGER library (DMCTrigger objects)  hd_eventfilter Nominal goal for L3 is to discard 90% of L1-accepted events 9/27/1314simulation status - D. Lawrence - JLab

15. Energy deposition in FCAL 1 GeV 2 GeV 9/27/1315simulation status - D. Lawrence - JLab ++ ++  detector FCAL GEANT3 simulation by Lubomir Pentchev GEANT3 GEANT4 Trigger depends strongly on FCAL response Particle ID depends on BOTH FCAL and  detector response Currently have limited ability to simulate FCAL response to hadronic showers

16. Some ideas on what is needed next … Implement muon detector in HDDS and test with hdgeant4 – Devise code management system to maintain CPP specific geometry while keeping aligned with geometry shared with GlueX (e.g. FDC) Simulations of  separation with refined muon/pion detector design Tracking in  detector ? Complete implementation of relevant reactions in GlueX ANALYSIS package –  p -> p  +  - –  p -> p  o Full-scale simulation and extraction of signal reaction with all relevant backgrounds –  meson – Incoherent  +  - ? Simulate Polarization measurement using Primakoff asymmetry with: – 70% polarization – Realistic trigger – Backgrounds 9/27/13simulation status - D. Lawrence - JLab16

17. 9/27/13simulation status - D. Lawrence - JLab17

18. Backgrounds Experiment will measure reaction:  Pb -> Pb  +  - Primary background will be coherent  o production followed by  ->  decay – Will use angular distributions to separate Primakoff from coherent  o production (see later slides) Currently gathering list of other potentially relevant backgrounds including: –  meson production (angular distributions same as Primakoff) – incoherent  +  - production – … 9/27/1318simulation status - D. Lawrence - JLab

19. Relating cross-section to     9/27/1319 Figure 5. from Pasquini et al. Phys. Rev. C 77, 065211 (2008) Cross-section for  ->     calculated based on two values of     :     = 13.0 x 10 -4 fm 3 (top, dotted line)     = 5.7 x 10 -4 fm 3 (solid and dashed lines) Cross-section varies by ~10% for factor of 2 variation in     Need measurement of  ->      at few percent level  ->     dotted: subtracted DR calculation with     = 13.0 dashed: subtracted DR calculation with     = 5.7 solid: unsubtracted DR calculation with     = 5.7 Invariant mass of         = 13.0     = 5.7 (Data points from MARK-II) simulation status - D. Lawrence - JLab

20. Detector Rates/Acceptance 10 7 tagged photons/second on 5% radiation length Pb target 500 hours of running W  acceptance down to ~320 MeV/c 2 (working to improve acceptance to even lower W   Estimated ~36k* Primakoff events (contrast this with the ~400 events in the acceptance of the MARK-II measurement) 209/27/13 * before detector acceptance simulation status - D. Lawrence - JLab

21. Charged Particle Tracking Source code is checked out and built via nightly cron job on 3 platforms Twice a week cron jobs automatically simulate and reconstruct single track events and multi-track b 1  events Plots from 5/4/12 semi-weekly single track tests o Tracking code development began in 2004 o Tracking is done in multiple stages: Track Finding Wire-based fitting (wire positions only) Time-based fitting (drift times used) o Fitting done using a Kalman Filter (replaced original least-squares fitter) 9/27/1321simulation status - D. Lawrence - JLab

22. Charged Particle Tracking Plots from 5/7/12 semi-weekly b 1  tests Results of recent semi- weekly test doing full reconstruction of b 1  events Final state: p  +  +  -  -  (5 charged tracks) Some mis-identification of  + and proton exists >60% reconstruction efficiency of “X” meson 9/27/1322simulation status - D. Lawrence - JLab

23. Calorimetry FCAL Code developed based on experience with Rad-  experiment in Hall-B Full reconstruction (GlueX-doc-823) Depth corrections (GlueX-doc-1093) Calibration procedure established BCAL o 1 st generation Code developed copied from KLOE and adapted to GlueX o 2 nd generation currently under development by GlueX Improved angular resolution Better error estimation Increased  o reconstruction efficiency (61%->73% 11/28/11 report) FCAL reconstruction efficiency Red: min blocks = 1 Black: min blocks = 2 BCAL reconstructed energy resolution 9/27/1323simulation status - D. Lawrence - JLab

24. 9/27/1324  invariant mass w/ vertex constraint w/o vertex constraint simulation status - D. Lawrence - JLab