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AnDY @ IP2 MC

AnDY @ IP2 MC. Simulating DY and Backgrounds Geant3 Model of AnDY Single particle GEANT studies for background suppressions Fast simulation – Estimate of backgrounds Comparison of Simulation with Run11 Data Magnet and tracking. Akio Ogawa BNL 2012 Mar 31. DY. DY : ~7 x 10 -5 mb

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AnDY @ IP2 MC

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  1. AnDY @ IP2 MC Simulating DY and Backgrounds Geant3 Model of AnDY Single particle GEANT studies for background suppressions Fast simulation – Estimate of backgrounds Comparison of Simulation with Run11 Data Magnet and tracking Akio Ogawa BNL 2012 Mar 31

  2. DY DY : ~7 x 10-5 mb @ 500GeV Hadronic : ~30mb 106 Hadron & photon backgrounds Charm & bottom backgrounds Need >100 G hadronic events to simulate backgrounds http://spin.riken.bnl.gov/rsc/write-up/dy_final.pdf

  3. e+e- DY expectations at large xF at √s=500 GeV Note scale of signal for same L Proposed Run13 AnDY configration reasonable efficiency can be obtained for large-xF DY with existing equipment

  4. Lepton daughters from γ* • Most important contributions for γ* at xF>0.1 at √s=500 GeV … • high energy electrons and positrons (E>10 GeV) • require detection at very forward angles • e+(e-) from γ* little affected by “modest” isolation (20mr half-angle cone) • best solution for charge sign would be a dipole magnet (difficult for collider)

  5. Geant Model for Run-11 • BBC and ZDC/ZDC-SMD • HCal is existing 9x12 modules from E864 (NIM406,227) • Small (~120 cells) Ecal • 1 layer Pre-shower detector • Goal: • Establish impact of 3 IR operation on PheniX and STAR luminosity • Calibrate Hcal absolute energy scale with r, f, Ks • Measure hadronic background to bench mark MC further • AN for jet?

  6. Geant Model for Run-13

  7. Single particle GEANT studyPreshower 1 : photon rejection GEANT simulation of a pre-shower detector made of 0.5cm thick plastic scintillation counter. Responses for 30GeV electrons and photons are simulated. A cut of 0.5MeV < dE < 1.5MeV will retain 86% of electrons, while rejecting 98% photons including ones converted to e+e- pairs in beam pipe and preshower detector itself. Retain 86% electrons (and charged hadrons) Reject 98% photons

  8. Single particle GEANT studyPreshower 2 : hadron/photon rejection GEANT simulation of 2nd pre-shower detector made of 0.5cm thick plastic scintillation counter placed after 1cm Pb converter. Responses for 30GeV electrons, charged pion and photons are simulated. A cut of energy deposit in the 2nd pre-shower above 5MeV will retain 98% of electrons, while rejecting 85% of pions and 39% of photons. Retain 98% electrons Reject 85% hadrons Reject 39% photons

  9. Single particle GEANT study ECAL hadron response ½ hadrons leave MIP in ECAL Remaining ½ leave a fraction of evergy in Ecal, thus “mismeasure” hadron energy. With falling energy spectra of hadrons, ~1/100 suppression of hadron just due to response in ECAL GEANT simulation of EMcal response to E>15 GeV π± from PYTHIA 6.222 incident on (3.8cm)2x45cm lead glass calorimeter. GEANT response not so different from 57-GeV pion test beam data from CDF [hep-ex/0608081]

  10. Single particle GEANT studyECAL hadron response : MC Uncertainty GEANT simulation with hadronic interaction package GEISHA (black) and GCALOR(red) of energy deposited in an EMcal built from 3.8 cm × 3.8 cm × 45 cm lead glass bars. Charged pions with E=30 GeV are used in this simulation. The fraction of the incident pion energy deposited in the EMcal is f.

  11. Single particle GEANT studyHcal : hadron rejection GEANT simulation for energy deposit in an EMcal and Hcal for 30GeV electrons and charged pions. A 3x3 cluster sum of deposited energy forms the ratio R=DE(EMcal)/(DE(EMcal)+DE(Hcal)) shown in top plot. With R>0.9 cut, EMcal+Hcal can reject 82% of hadrons while retaining 99% of electrons. The bottom plot shows distribution of f for hadrons that survive R>0.9 cut. Retain 99% electrons (and photons) Reject 82% charged hadrons

  12. Single particle GEANT studyHcal : hadron rejection GEANT simulation for energy deposit in an EMcal and Hcal for 30GeV charged pions. The top plot shows the distribution of f in EMcal 3x3 clusters around the high tower. The bottom plot shows the ratio R=DE(EMcal)/(DE(EMcal)+DE(Hcal)). Blue shaded area is for hadrons surviving cut f>0.7. Red shaded area is hadrons which can be identified using Hcal by R>0.94 cut. This gives 40% hadron rejection for hadrons with f>0.7. Retain 99% electrons (and photons) Reject 40% charged hadrons which left >70% of energy in ECal

  13. ECAL photon rejection Pi0 peaks from Run11 Data Reconstructing pi0 (and eta) reduces Photon background by ~90%

  14. GEANT CPU time/Storage for background simulation • 100G MinBias events for background • Filter for background at Pythia level cannot be very effective (~ 1/10) • ~5sec/event * 10G = 50Gsec = 1.5k CPU years • With 10K CPU = 1 ½ month • Simplified HCAL model in GEANT ~x3 in speed • Smarter Pythia filter ? • Storage: ~10k byte/event * 10G = 100T byte (Filter after geant to reduce storage req)

  15. Fast Simulation based on single particle geant studies • ~1012 p+p interactions in 50 / pb at √s=500 GeV ⇒ full PYTHIA/GEANT not practical • Parameterize GEANT response of EMcal and use parameterized response in fast simulator applied to full PYTHIA events • Estimate rejection factors from GEANT for hadron calorimeter and preshower detector (both critical to h±/e± discrimination) • Explicit treatment in fast simulator to estimate path lengths through key elements (beam pipe and preshower), to simulate photon conversion to e+e- pair • Estimate effects from cluster merging in EMcal (d < εdcell / use ε=1 for estimates) • Estimate/simulate EMcal cluster energy and position resolutions. σE=15%/√E and σx(y)=0.1dcell, used to date for π0→γγ rejection.

  16. QCD Background Estimate from Fast Simulation • Comments: • Conversion photons significantly reduced by π0→γγ veto • Preshower thickness tuned, although perhaps is not so critical given photon veto • Linearly decreasing dN/df estimates smaller hadronic background ⇒ increased sophistication needed for reliable estimates, although other model uncertainties could easily dominate.

  17. Open Bottom Background Estimate from Fast Simulation

  18. Data & Geant ComparisonsHcal as Ecal

  19. Hcal Cell by Cell Calibrationusing pi0 peaks

  20. Data & Fast Simulation comparison

  21. Magnetic Field Used for Charge Sign Simulations • The plan is to reuse the split-dipole magnet at IP2 designed, built and operated by the PHOBOS collaboration. • PHOBOS provided their field map and geometry files for GEANT for simulation studies. • Compared to use at IP10, split-dipole is rotated by 180o around vertical axis, to move aperture restriction from coils close to IP. • the magnetic field calculation by Wuzheng Meng that opens the gap between the poles of the split dipole to 31.4 cm Interaction Point Vertical component of B versus x,z at y=0 from modified PHOBOS split-dipole magnet

  22. Charge sign

  23. Conclusion

  24. Backup

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