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Feasibility of   γγ study with ECAL

Feasibility of   γγ study with ECAL. Sergey Kiselev, ITEP Moscow, for the ECAL group Introduction Input info and assumptions Acceptance γ s pectra γ origin S/B vs resolution S/B vs p t S/B vs E beam S/B vs WA98 data Conclusions. Introduction: previous conclusions (10 th CBM).

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Feasibility of   γγ study with ECAL

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  1. Feasibility of  γγ study with ECAL • Sergey Kiselev, ITEP Moscow, for the ECAL group • Introduction • Input info and assumptions • Acceptance • γ spectra • γorigin • S/B vs resolution • S/B vs pt • S/B vs Ebeam • S/B vs WA98 data • Conclusions 12th CBM Collaboration meeting, Dubna S.Kiselev ITEP

  2. Introduction: previous conclusions (10th CBM) • OCT04, central Au+Au 25 AGeV, 2 arms ECAL •   γγ:S/B ~ 0.1 – 0.3 % • π0 ID  higher S/B (~ 25% ) • higher pγcut ( > 1 GeV/c)  higher S/B (80% ) 12th CBM Collaboration meeting, Dubna S.Kiselev ITEP

  3. Input info and assumptions • CbmRoot package (AUG07), Geant3 • 105 UrQMD Au+Au central events at E/A=15, 25, 35 GeV • ECAL: energy resolution σE = 3%/√E, 6%/√E, 9%/√E, ideal γ and πo  2γ reconstruction • Central rapidity region  the ECAL ring:lab = 90 – 200 , ρ = 190 – 440 cm, S = 49 m2 • pγ cut: pγ > 0.3 GeV/c 12th CBM Collaboration meeting, Dubna S.Kiselev ITEP

  4. Central rapidity region lab = 90 – 200 15 AGeV: c.m. = 500 – 900 25 AGeV: c.m. = 600 – 1050 35 AGeV: c.m. = 700 – 1150 12th CBM Collaboration meeting, Dubna S.Kiselev ITEP

  5. Acceptance 25 AGeV 1 event: ~ 12 primary  Br = 40%  5   γγ ~ 10% of   γγ are in the ECAL ring 12th CBM Collaboration meeting, Dubna S.Kiselev ITEP

  6. γspectra 25 AGeV 12th CBM Collaboration meeting, Dubna S.Kiselev ITEP

  7. γorigin 25 AGeV π0 e  TOF STS TRD RHIC 12th CBM Collaboration meeting, Dubna S.Kiselev ITEP

  8. S/B2σ vs resolution 25 AGeV Signal width (~10, 20, 30 MeV) ~ energy resolution (3, 6, 9%) 12th CBM Collaboration meeting, Dubna S.Kiselev ITEP

  9. S/B2σ vs pt 25 AGeV, 6%/√E Signal width =21, 19, 16 MeV for pt = 0.4-0.8, 0.8-1.2, 1.2-1.6 GeV/c 12th CBM Collaboration meeting, Dubna S.Kiselev ITEP

  10. S/B2σ vs Ebeam 6%/√E S/B ~ 1/(γ mult.) 12th CBM Collaboration meeting, Dubna S.Kiselev ITEP

  11. S/B2σ (%) vs (Ebeam, pt ) For significance ~ 10, ~107 events needed 12th CBM Collaboration meeting, Dubna S.Kiselev ITEP

  12. 2 arms vs the ring 12th CBM Collaboration meeting, Dubna S.Kiselev ITEP

  13.   γγWA98 data nucl-ex/0006007 σ/E=5.5%/√E 6.7 106central events mixed event technique S/B ~ 0.3% Our S/B estimation is in reasonable agreement with the WA98 data. UrQMD overestimates (~30%) pion yields. Our S/B should be multiplied by a factor ~ 1.5 12th CBM Collaboration meeting, Dubna S.Kiselev ITEP

  14. WA98: π0 suppression in central Pb+Pb nucl-ex/0701043: π0 data for p+C, p+Pb as reference for Pb+Pb π0 suppression  lower background  larger S/B 12th CBM Collaboration meeting, Dubna S.Kiselev ITEP

  15. Conclusions and next steps • OCT04 and AUG07 are in reasonable agreement •   γγ:S/B ~ 0.1 – 0.3 % • higher pγ higher S/B • For significance ~ 10, 107 events needed. • WA98: S/B =0.3% by mixed event technique • Next step: take into account γ reconstruction efficiency 12th CBM Collaboration meeting, Dubna S.Kiselev ITEP

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