1. Status of the FOPI pp Beamtime -Motivation -Particle Reconstruction -Inclusive Reconstruction -Exclusive Reconstruction with kinematical Refit -Summary and Outlook

2. Motivation

3. p Kaonic bound states Λ(1405) Doorway Mechanism   p  Λ  p  p + 3 T. Yamazaki et T. Akahishi, Phys. Rev. C 76 (2007) 045201 p–K - Potential Robert Münzer Leannis Meeting – Prag – May 2012

4. N* - Resonances Robert Münzer Leannis Meeting – Prag – May 2012 4 Production Mechanism: p + p -> p + K + + Λ M. S.-W. : Eu. Phys. Jou. A 46

5. The Experiment

6.  (Start – RPC) : 200 ps S(Start – PLAWA) : 400 ps Exclusive measurement: p-beam@3.1 GeV Target: 2cm Liquid Hydrogen 80 Million LVL2 Trigger Events p + p  - + p + K + ppK -  + p  (1405) + p + K + 3.1 GeV Beam Magnet CDC Barrel RPC Helitron PLAWA Robert Münzer Leannis Meeting – Prag – May 2012 6

7. SiLViO Beam Magnet CDC Barrel RPC Helitron PLAWA Robert Münzer Leannis Meeting – Prag – May 2012 7

8. Polar angle of particles from Λ decay (pK + Λ / K + in RPC acceptance) LVL1 / LVL2: Signal (pK + Λ): 5.8 Background (UrQMD pp 3.1GeV): 20.3 LVL1 / LVL2: Signal (pK + Λ): 5.8 Background (UrQMD pp 3.1GeV): 20.3 Trigger conditions LVL1: M(TOF) > 1 LVL2: LVL1 + SiΛVIO Trigger conditions LVL1: M(TOF) > 1 LVL2: LVL1 + SiΛVIO Silicon Λ-Vertexing and Identification Online SiΛViO 8 M>0 M>1 NIMA617:300-302,2010 SiΛViO Acceptance Robert Münzer Leannis Meeting – Prag – May 2012

9. Particle Selection

10. Particle Identification 10 Backward Hemisphere CDC momentum + energy loss Backward Hemisphere CDC momentum + energy loss Forward Hemisphere Helitron momentum + Plawa TOF Forward Hemisphere Helitron momentum + Plawa TOF Preliminary Robert Münzer Leannis Meeting – Prag – May 2012

11. Calibration not final Kaon Identification Time of Flight Detectors: Resistive Plate Chambers (RPC) Preliminary 11 Robert Münzer Leannis Meeting – Prag – May 2012

12. -- p Λ Inclusive Reconstruction

13. Inclusive Λ Reconstruction Data pp Simulation Preliminary 13 Λ  p CDC HELITRON Si  ViO RPC Robert Münzer Leannis Meeting – Prag – May 2012

14. Inclusive Λ Reconstruction Data LVL2 Data LVL1 Enhancement: > 4,4 Fits to simulation Enhancement: > 4,4 Fits to simulation Preliminary 14   p CDC HELITRON Si  ViO RPC Robert Münzer Leannis Meeting – Prag – May 2012

15. Exlcusive Reconstruction K+K+ -- p 

16. Kinematical Refit Modify Particle Track Parameters (mom, phi, theta) within error to fulfill contraints. Results: New Particle Track Parameters,   16 Background Robert Münzer Leannis Meeting – Prag – May 2012 Diploma Thesis D. Pleiner Diploma Thesis D. Pleiner

17. Kinematical Refit Conservation Constraint 17 K+K+ p p p p (E,p) beam (E,p) target (E,p) kaon (E,p) pion (E,p) secproton (E,p) primproton p p p p π-π- π-π- K+K+ K+K+ Λ Λ E secproton + E pion + E primproton + E kaon = E beam + E target p secproton + p pion + p primproton + p kaon = p beam + p target E secproton + E pion + E primproton + E kaon = E beam + E target p secproton + p pion + p primproton + p kaon = p beam + p target Robert Münzer Leannis Meeting – Prag – May 2012

18. Kinematical Refit Mass Constraint 18 K+K+ p p p p (E,p) beam (E,p) target (E,p) pion (E,p) secproton (E,p) primproton p p p p π-π- π-π- K+K+ K+K+ Λ Λ { (E,p) secproton + (E,p) pion }² = M(Λ)² (E,p) kaon Robert Münzer Leannis Meeting – Prag – May 2012

19. Kinematical Refit Mass Constraint 19 K+K+ p p p p (E,p) beam (E,p) target (E,p) pion (E,p) secproton (E,p) primproton p p p p π-π- π-π- K+K+ K+K+ Λ Λ Vertex Constraints: Intersection p and π (E,p) kaon Robert Münzer Leannis Meeting – Prag – May 2012

20. Kinematical Refit Mass Constraint 20 K+K+ p p p p (E,p) beam (E,p) target (E,p) pion (E,p) secproton (E,p) primproton p p p p π-π- π-π- K+K+ K+K+ Λ Λ Vertex Constraints: Intersection p and K + (E,p) kaon Robert Münzer Leannis Meeting – Prag – May 2012

21. Kinematical Refit Mass Constraint 21 K+K+ p p p p (E,p) beam (E,p) target (E,p) pion (E,p) secproton (E,p) primproton p p p p π-π- π-π- K+K+ K+K+ Λ Λ Vertex Constraints: Primary & Secondary Vertex (E,p) kaon Robert Münzer Leannis Meeting – Prag – May 2012

22. Exlcusive Reconstruction pp – Simulation (URQMD) K+K+ -- p 

23. Conservation Constraint E secproton + E pion + E primproton + E kaon = E beam + E target p secproton + p pion + p primproton + p kaon = p beam + p target E secproton + E pion + E primproton + E kaon = E beam + E target p secproton + p pion + p primproton + p kaon = p beam + p target

24. pval> 0.007 Conservation Constraint Robert Münzer Leannis Meeting – Prag – May 2012 24

25. Invariant mass (p, π) With refit Without refit Robert Münzer Leannis Meeting – Prag – May 2012 25

26. Conservation + Mass Constraint E secproton + E pion + E primproton + E kaon = E beam + E target p secproton + p pion + p primproton + p kaon = p beam + p target E secproton + E pion + E primproton + E kaon = E beam + E target p secproton + p pion + p primproton + p kaon = p beam + p target { (E,p) secproton + (E,p) pion }² = M(Λ)²

27. Invariant mass (p, π) With refit Without refit Robert Münzer Leannis Meeting – Prag – May 2012 27 pval>0.007

28. Missing Mass(p) Without Refit With Refit N* included in Urqmd Robert Münzer Leannis Meeting – Prag – May 2012 28 pval>0.007 p+p -> p + N* ( -> Λ + K + )

29. Exlcusive Reconstruction Data K+K+ -- p 

30. Data Original pval cut(>0.87) Original Invariant Mass (p,π) Energy & Momentum Contraint

31. N* MM (p) - refitted Pp UrQMD MM (p) - refitted Data Unrefitted refitted |Inv(p,pi)-1.116|<40 Mev Robert Münzer Leannis Meeting – Prag – May 2012 31

32. Systematical Errors Primary proton pion 1/p ϑ φ Robert Münzer Leannis Meeting – Prag – May 2012 32

33. Summary & Outlook Inclusive Lambda-Routine: – Lambda are visible in Semi Forward Kombination – Reduction Compareable with Simulations Exclusive Reconstruction tested with simulation – Event Selection: Refit is sensitive to Different Channels – Additional Constraints (Vertex) has to be tested. – Resolutiuon can be improved signal: N* signal as a crosscheck Refit with Data – Pval Cut reduced Background of Exclusive Lambda. – N*- signal visble : Crosscheck of analysis – Problem: Systematical Errors New Calibration – Finished recently. Has to be tested.

34. Backup

35. Different Regions   p CDC HELITRON Si  vio RPC   p CDC HELITRON Si  vio RPC Semi – Forward (CDC – (RPC) ) Forward (Si  ViO – Helitron - Plawa) 35 Polar angle of particles from Λ decay (pK + Λ / K + in RPC acceptance) Robert Münzer Leannis Meeting – Prag – May 2012

36. Event Selection - - + + + + + + Available tracks 4 5 + + 3 21 Pi- cand 1 Pi- cand 1 K + - Cand 1 K + - Cand 1 P- cand 1 P- cand 2 P- cand 2 Rough PID 4 5 p- cand 3 p- cand 3 3 21

37. Pi- cand 1 Pi- cand 1 K + - Cand 1 K + - Cand 1 P- cand 1 P- cand 2 P- cand 2 Bild Kombination p- cand 3 p- cand 3 Pi- cand 1 Pi- cand 1 P- cand 1 K + - Cand 1 K + - Cand 1 P- cand 2 P- cand 2 Pi- cand 1 Pi- cand 1 P- cand 2 K + - Cand 1 K + - Cand 1 P- cand 1 P- cand 1 Komb 1Komb 2 Pi- cand 1 Pi- cand 1 P- cand 1 K + - Cand 1 K + - Cand 1 P- cand 3 P- cand 3 Komb 3Komb i

38. Prefit Komb (i) Prefit Komb (i) Chi2 - Pval

39. Prefit Komb (i) Sort descending by pval Komb 1 (biggest pval) will be used Chi2 - Pval Remaining particle is treated as faketrack Best

40. Lambda Preselection Preselectio Option 2: 75% of Lambda Kombination are select

41. Main Fit Orig Komb 1 (biggest pval) will be used Best Refit Ref Komb 1 (biggest pval) will be used Best Ntuple Chi2 Pval Inv(p,π) Inv(Λ,p) Inv(Λ,K) mm(p) mm(K) rInv(p,π) rInv(Λ,p) Inv(Λ,K)r rmm(p) rmm(K) mm(K,p) rmm(K,p) Vertices rVertices

42. Conservation Constraint Pval > 0.1

43. Conservation Constraint all pkΣ

44. Conservation Constraint all pkΣ Best Value: 0.0007

45. Conservation Constraint

46. Missing Mass (p, K)

47. Different Contraints Conservation Conservation+ Mass

48. Invariant Mass (p,π)

49. Invariant mass (p, π) Conservation Conservation+ Mass

50. Missing Mass (p)

51. Conservation Conservation+ Mass N* included in Urqmd

52. Missing Mass(p) Conservation pKL - Phasespace N* included in Urqmd

53. Missing Mass (p, K)

54. Different Contraints Conservation Conservation+ Mass

55. Exlcusive Reconstruction Data K+K+ -- p 

56. Data Original pval cut(>0.87) Original Invariant Mass (p,π) Energy & Momentum Contraint

57. Data Refitted Original Missing Mass pK+ μ=1.132 σ=0.039 μ=1.132 σ=0.039 μ=1.24 σ=0.050 μ=1.24 σ=0.050 |InvM(p,p)-1.116|<0.02 Pval.ne.0 |InvM(p,p)-1.116|<0.02 Pval.ne.0 Energy & Momentum Contraint μ=1.112 σ=0.016 μ=1.112 σ=0.016

58. Absolutely Preliminary Data pkL Phasespace Missing mass K (refitted)

59. Refit