ITEP meeting S.Kiselev1 RQMD: p+C  γ X at T=5.13 GeV 2-arms FLINT  Sergey Kiselev, ITEP Moscow  Acceptance  Input info  Multiplicities  Initial π 0 spectra  Initial nucleon spectra  γ multiplicity  γ spectra  π 0 spectra  γ from π 0  ΔR γγ distributions  M γγ distributions

Acceptance: 80x80 cm 2, 250 cm from a target, arms centers at (X,Y) = (44,0) and (-44,0) 1 arm2 arms ITEP meeting S.Kiselev2

Acceptance vs X-axis, no p cut 1 arm2 arms ITEP meeting S.Kiselev3

Acceptance + p cut 2 arms2 arms + p>400 MeV/c ITEP meeting S.Kiselev4

Acceptance + p cut 1 arms + p>400 MeV/c2 arms + p>400 MeV/c ITEP meeting S.Kiselev5

ITEP meeting S.Kiselev6 Input info  RQMD4.12 generator  10 5 min. bias (b<R C =2.5 fm) p+C events as at T=5.13 GeV  Two arms FLINT: 80x80 cm 2 at 250 cm from the target, arm centers: (X,Y)=(44,0) and (=-44,0)  θ =  Only γ from π 0 will be analyzed  Low momentum cut: 400 MeV/c.  Energy resolution: 6%/√E  Space resolution: cell size 10x10 cm 2  momentum is matched to the center of a cell  Trigger: p γ > 0.4 GeV/c, i.e. without a trigger

Multiplicity of participants ITEP meeting S.Kiselev7 ~20% of events without participants, only projectile proton, no b 2 dependence

Multiplicity of species ITEP meeting S.Kiselev8 Multiplicity normalized on events with participants GEANT numbers of particles 1. gamma 13. n0 25. n~0 37. D0 2. e+ 14. p+ 26. Lambda~0 38. D~0 3. e- 15. p~- 27. Sigma~- 39. D_s+ 4. neutrino 16. K_S0 28. Sigma~0 40. D_s- 5. mu+ 17. eta 29. Sigma~+ 41. Lambda_c+ 6. mu- 18. Lambda 30. Xi~0 42. rho+ 7. pi0 19. Sigma+ 31. Xi~+ 43. rho- 8. pi+ 20. Sigma0 32. Omega~+ 44. rho0 9. pi- 21. Sigma- 33. omega 45. deut 10. K_L0 22. Xi0 34. phi 46. t 11. K+ 23. Xi_ 35. D+ 47. He4 12. K- 24. Omega- 36. D- 48. Geantino

Initial π 0 spectra ITEP meeting S.Kiselev9 cosθ =  θ =

Initial nucleon spectra protons neutrons ITEP meeting S.Kiselev10 p with p>5.8 GeV/c have σ cosθ ~  θ = 4 0

Protons with p>5.8 GeV/c ITEP meeting S.Kiselev11 ~10% of events have “beam” proton from pN interaction

Protons with p>5.8 GeV/c ITEP meeting S.Kiselev12 Examples of events: nrhead=6, bimpact= , geantCode=14, nspect=0, lcoll=1, p= , theta= nrhead=0, bimpact= , geantCode=14, nspect=0, lcoll=1, p= , theta= nrhead=6, bimpact= , geantCode=14, nspect=0, lcoll=1, p= , theta= nrhead=0, bimpact= , geantCode=13, nspect=0, lcoll=1, p= , theta= nrhead=6, bimpact= , geantCode=14, nspect=0, lcoll=1, p= , theta= nrhead=0, bimpact= , geantCode=14, nspect=0, lcoll=1, p= , theta= nrhead=0, bimpact= , geantCode=13, nspect=0, lcoll=1, p= , theta=

γ multiplicity 1 arm2 arms ITEP meeting S.Kiselev13 ~5% events with > 0 γ, ~1% with > 1 γ~10% events with > 0 γ, ~2% with > 1 γ

γ spectra 1 arm 2 arms ITEP meeting S.Kiselev14 excess over γ from π 0 due to events with 1 γ

π 0 spectra 1 arm2 arms ITEP meeting S.Kiselev15 2 arms  ~2.7 times larger number of π 0

γ from π 0 1 arm2 arms ITEP meeting S.Kiselev16 one can choose the trigger value

ΔR γγ distribution 1 arm2 arms ITEP meeting S.Kiselev17 More than 2 cells between γγ

ΔR γγ from π 0 vs P 1 arm2 arms ITEP meeting S.Kiselev18

M γγ distribution 1 arm2 arms ITEP meeting S.Kiselev19 width of the signal ~ 20 MeV, 2 arms  larger background S/(S+B)= 96% S/(S+B)= 84%

ITEP meeting S.Kiselev20 Conclusions  10 5 RQMD p+C events at T=5.14 GeV  ~20% of events without participants, only projectile proton  ~10% events have “beam” proton at θ =  2 arms  ~2 times larger events with γ  2 arms  ~2.7 times larger number of π 0  2 arms  larger background, but still small, S/(S+B) ~ 84% instead of S/(S+B) ~ 96%