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- 0 discrimination in the Alice EMCal

This study explores γ-π0 discrimination in the Alice EMCal using tower size and separation, as well as shower shape analysis. Results show potential for improved discrimination with the new geometry.

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- 0 discrimination in the Alice EMCal

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  1. -0 discriminationin the Alice EMCal Marco van Leeuwen, LBNL Based on work by: Heather Gray (Master’s thesis)

  2.  0 2 1 New tower size (0.014) 0 Two EMCal tower separation Adjacent EMCal towers -0 discrimination  separation Tower size: 0.012x0.012 (old geometry)

  3. -0 discrimination increasing pT < 6 GeV/c well separated clusters  invariant mass analysis • ~6 - 25 GeV/c • merged clusters • not spherical • shower shape analysis • > 25 GeV/c • Opening angle < 1 cell • all 0’s at this energy are in jets isolation cut Three regions of analysis

  4. Shower shape analysis  Merged clusters but shape differs  Different shower shape parameters can be used to discriminate • dispersion ~ cluster width • sphericity • 0~length of longest cluster axis  Calculated using logarithmic energy weighting   T.Awes et al, NIM Phys. Res. A 321, p152

  5. Shower shape distributions 14-16 GeV p0 and g Inclusion of material has relatively small effect Background event gives significant deterioration Depends on tower energy cut: 200 MeV for this simu, 500 MeV significantly better

  6. Shower shape cut performance l0 cut value p0 contamination rises at 40-50 GeV i.e. when separation << 1 tower

  7. Expected rates Conclusion g/p0 separation power ends where yield dwindles Or: granularity matches expected yields 10k/year 50 GeV

  8. First look at new geometry Plots from Subhasis, Aleksei New geometry High-granularity shlaslick g eff./p0 eff. g eff./p0 eff. 30 GeV: some discimination power Cross check:higher granularity helps 50 GeV: discrimination power small g efficiency g efficiency Results consistent with expectations New geometry results similar to old geometry

  9. To do list • Collect results for review • Redo simulations with new geometry(and lower cut-off in Geant) • Beam test to check shower shapes • Not urgent: • Invariant mass analysis for p0 • Isolation cuts

  10. Extra slides

  11. Conversions About 55% of photons survive all the material

  12. Material distribution h-j shower points (before EMCal) x,y conversion points

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