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RQMD: p+C γ X at T=5.13 GeV 2-arms FLINT

Sergey Kiselev, ITEP Moscow Acceptance Input info Multiplicities Initial π0 spectra Initial nucleon spectra γ multiplicity γ spectra π0 spectra γ from π0

ΔRγγ distributions Mγγ distributions

Acceptance: 80x80 cm2, 250 cm from a target, arms centers at (X,Y) = (44,0) and (-44,0)

1 arm 2 arms

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Acceptance vs X-axis, no p cut

1 arm 2 arms

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Acceptance + p cut

2 arms 2 arms + p>400 MeV/c

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Acceptance + p cut

1 arms + p>400 MeV/c 2 arms + p>400 MeV/c

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Input info RQMD4.12 generator 105 min. bias (b<RC =2.5 fm) p+C events as at T=5.13 GeV

Two arms FLINT: 80x80 cm2 at 250 cm from the target, arm centers: (X,Y)=(44,0) and (=-44,0) θ = 10 - 190

Only γ from π0 will be analyzed Low momentum cut: 400 MeV/c. Energy resolution: 6%/√E Space resolution: cell size 10x10 cm2 momentum is

matched to the center of a cell Trigger: pγ > 0.4 GeV/c, i.e. without a trigger

Multiplicity of participants

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~20% of events without participants, only projectile proton, no b2 dependence

Multiplicity of species

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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 π0 spectra

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cosθ = 0.999 θ = 30

0.998 4 0.996 5 0.994 6 0.992 7 0.99 8 0.98 11 0.97 14 0.96 16 0.95 18

Initial nucleon spectra

protons neutrons

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p with p>5.8 GeV/c have σcosθ ~ 0.998 θ = 40

Protons with p>5.8 GeV/c

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~10% of events have “beam” proton from pN interaction

Protons with p>5.8 GeV/c

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Examples of events:

nrhead=6, bimpact=2.241061, geantCode=14, nspect=0, lcoll=1, p=5.961061, theta=2.842756nrhead=0, bimpact=2.241061, geantCode=14, nspect=0, lcoll=1, p=0.165105, theta=65.570152

nrhead=6, bimpact=2.007447, geantCode=14, nspect=0, lcoll=1, p=5.907417, theta=2.537880nrhead=0, bimpact=2.007447, geantCode=13, nspect=0, lcoll=1, p=0.405312, theta=59.483635

nrhead=6, bimpact=2.316128, geantCode=14, nspect=0, lcoll=1, p=5.904437, theta=3.532158nrhead=0, bimpact=2.316128, geantCode=14, nspect=0, lcoll=1, p=0.104308, theta=108.291145nrhead=0, bimpact=2.316128, geantCode=13, nspect=0, lcoll=1, p=0.358224, theta=70.959030

γ multiplicity

1 arm 2 arms

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~5% events with > 0 γ, ~1% with > 1 γ ~10% events with > 0 γ, ~2% with > 1 γ

γ spectra1 arm 2 arms

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excess over γ from π0 due to events with 1 γ

π0 spectra

1 arm 2 arms

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2 arms ~2.7 times larger number of π0

γ from π0

1 arm 2 arms

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one can choose the trigger value

ΔRγγ distribution

1 arm 2 arms

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More than 2 cells between γγ

ΔRγγ from π0 vs P

1 arm 2 arms

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Mγγ distribution

1 arm 2 arms

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width of the signal ~ 20 MeV, 2 arms larger background

S/(S+B)= 96%

S/(S+B)= 84%

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Conclusions

105 RQMD p+C events at T=5.14 GeV ~20% of events without participants, only

projectile proton ~10% events have “beam” proton at θ = 00 -40

2 arms ~2 times larger events with γ 2 arms ~2.7 times larger number of π0 2 arms larger background, but still small,

S/(S+B) ~ 84% instead of S/(S+B) ~ 96%