1. Pi0 Reconstruction with High p t Photons John Chin-Hao Chen

2. Outline Reconstruction of π 0 Purity of π 0 Summary

3. Reconstruct π 0 s By π 0 -> γ γ γ 1 = (E 1, p 1 ), γ 2 = (E 2, p 2 ), then m inv =sqrt((E 1 -E 2 ) 2 + (p 1 -p 2 ) 2 ) Pair all photons pass the cuts, calculate it ’ s invariant mass. High p t (>5 GeV/c) as trigger photon Combine trigger photons with low p t (>0.5 GeV/c) partner photons.

4. Photon Detector: EMCal Use EMCalorimeter to detect photon showers 6 PbSc, 2 PbGl detectors

5. Photon Cuts Trigger photons: Zvertex <30 cm Not in bad run list Not in hot/ dead map pc3dz >5 && pc3dphi>0.01 chi2cut Fiducial cut: 0.882>Phi >-0.489, or 3.63>phi>2.26 Partner Photon: Hot /dead map cut Tighter: apply all the cuts as trigger photons

6. A typical result π 0 =(0.12,0.16) Trig E > 5 GeV Part E >0.5 GeV

7. Invariant Mass spectrum of trig E > 5 GeV & various part E η peak? (m = 548 MeV)

8. # of photons vs different partner energy cut

9. Cent: 0-20, no partner cuts Cent: 0-20, no partner cut

10. Cent:0-20, with partner cuts

11. Cent:60-92, with partner cut

12. Cent: 60-92, no partner cuts

13. Find π 0 Purity Purity =1- (background/total) π 0 window: 0.12 < m inv <0.16 GeV/c 2 π 0 peak: gaussian Background: linear Fit between (0.08,0.20)

14. Fit the π 0 Peak Cent: 0-20 No partner cut 5< Trig pt < 6 GeV/c Part pt >0.5 GeV/c π 0 peak =139+/-0.3 MeV/c 2 Purity =0.44 +/- 0.03

15. Part pt > 0.5 GeV/c, without partner cut

16. Part pt > 0.5 GeV/c, with Partner Cut

17. 5 <Trig pt <6 GeV/c, without Partner Cut

18. 5 <Trig pt <6 GeV/c, with Partner Cut

19. Summary π 0 s are reconstructed by pairing two photons with different cuts. Higher p t trigger photon has better purity. Higher p t partner photon has better purity. With partner cuts, the purity is better.

20. Backup slides

21. # of Tagged photons vs partner p t triggerpartner trig ptpart ptEntriesTotalTaggedUntaggedTotal Tagge d Untagge d 50.513005910397278776101300592787127272 51.022198103971236916122198123620962 51.5535110397746965153517464605 52.0171910397469992817194691250 52.57761039729310104776293483 53.04521039719210205452192260 53.52711039711910278271119152 54.01841039790103071849094 54.51191039757103401195762 55.078103973610361783642

22. A Typical Result Trig E > 5 GeV Part E >0.5 GeV

23. Spectrums of Trigger and Partner Photon Trig E > 5 GeV Part E >0.5 GeV

24. Cent :20-40, no partner cuts

25. Cent: 40-60, no partner cuts

26. Cent: 0-92, no partner cuts

27. Cent: 0-92, with partner cut

28. Cent: 20-40, with partner cuts

29. Cent: 40-60, with partner cuts