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Feasibility of   γγ study with ECAL

Feasibility of   γγ study with ECAL. Sergey Kiselev, ITEP Moscow, for the ECAL group Assumptions and input info γ s pectra Acceptance γ origin Signal Signal + background S/B   γγ WA98 data Conclusions. Assumptions and input info.

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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 • Assumptions and input info • γ spectra • Acceptance • γorigin • Signal • Signal + background • S/B •  γγ WA98 data • Conclusions 10th CBM Collaboration meeting, Dresden S.Kiselev ITEP

  2. Assumptions and input info • ECAL: energy resolution σE = 3%/√E, 6%/√E, 9%/√E, ideal γ and πo  2γ reconstruction • Central rapidity region for 25 AGeV  lab = 90 – 200 • Two arms ECAL, an example: 2 sectors, π coverage for  • Two pγ cuts: pγ > 0.3 GeV/c, pγ > 1 GeV/c • CbmRoot package (04.10.2004), Geant3 • 105 UrQMD Au+Au central events at E/A=25 GeV: standard files /d/cbm04/…/urqmd.auau.25gev.centr.0000.mc.root, ... 10th CBM Collaboration meeting, Dresden S.Kiselev ITEP

  3. γspectra (without pγ cut) 10th CBM Collaboration meeting, Dresden S.Kiselev ITEP

  4. Acceptance 1 event: ~ 12 primary  ~ 5   γγ ~ 0.1   γγ in the set up pγ > 0.3 GeV/c : ~0.1   γγ pγ > 1 GeV/c : ~0.04   γγ 10th CBM Collaboration meeting, Dresden S.Kiselev ITEP

  5. γorigin (pγ > 0.3 GeV/c) • ~ 80γ • ~ 90% from π0, ~ 4% from e, ~ 3% from • ~ 90% with ρvtx < 10 cm • ~ 7 γ from ID π0 (both γ in ECAL) 10th CBM Collaboration meeting, Dresden S.Kiselev ITEP

  6. Signal pγ > 0.3 GeV/c pγ > 1 GeV/c Signal width (~10, 20, 30 MeV) ~ energy resolution (3, 6, 9%) 10th CBM Collaboration meeting, Dresden S.Kiselev ITEP

  7. Signal + background pγ > 1 GeV/c pγ > 0.3 GeV/c Higher statistics needed 10th CBM Collaboration meeting, Dresden S.Kiselev ITEP

  8. S/B (2σ window) pγ > 0.3 GeV/c, with/withoutγ from ID π0 without γ from ID π0 ~ 25% higher S/B pγ > 0.3/1 GeV/c p > 1 GeV/c  ~ 80% higher S/B For significance ~ 10, 106events needed 10th CBM Collaboration meeting, Dresden S.Kiselev ITEP

  9.   γγWA98 data nucl-ex/0006007 σ/E=5.5%/√E mixed event technique S/B ~ 0.3% Our S/B estimation is in reasonable agreement with the WA98 data 10th CBM Collaboration meeting, Dresden S.Kiselev ITEP

  10. Conclusions •   γγ:S/B ~ 0.1 – 0.3 % • π0 ID  higher S/B (~ 25% ) • higher pγcut ( > 1 GeV/c)  higher S/B (80% ) • For significance ~ 10, 106 events needed. Not a problem for CBM with high intensity beam •   γγ can be extracted by mixed event technique 10th CBM Collaboration meeting, Dresden S.Kiselev ITEP

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