Λ *(1520) Photoproduction from LH 2 and LD 2

1. Λ*(1520) Photoproductionfrom LH2 and LD2 Jia-Ye Chen LEPS Collaboration Meeting In Taiwan

2. Outline • Physics Motivation • Previous Results : LAMP2 and CLAS • Data Analysis • Reaction Channels • Analysis Scenarios • Event Selections • Λ*(1520) production in Kp and KK detection modes • Background Linearity • K- decay asymmetry in Λ*(1520) Helicity frame • Side-Band Subtraction • Monte Carlo Background Fitting (By Muramatsu-san) • Total Cross Section of LH2 and LD2 • Summary

3. Physics Motivation γ＋ p → K+ + Λ*(1520) →K+ + p + K- Helicity Frame 1. If ONLY spinless kaon, K-, exchange → 2. If ONLY vector kaon, K*- ,exchange → (If solely determined by Clebsch-Gordon coefficients)

4. Assume LAMP2 Photoproduction CLAS Electroproduction Previous Results Q2≠0 Contribution

5. Reaction Channels • Production Channels LH2 LD2 • Background Channels LH2 LD2

6. Analysis Scenarios Side-Band Subtraction Monte Carlo Background Fitting Subtracting the background components from real data mass spectrum to get the count of Λ*(1520). Assuming that the background linearity is good, , the count in S0 region can be obtained accompany with the sneak-in factor from Monte Carlo simulation.

7. Kp mode ntrk > 1 3 sigma PID ikm/ipr ≠ 0 ithtofhit(ikm/ipr) > 0 prbchi2(ikm/ipr) ≥ 0.02 abs(ytof(ikm/ipr)-tofdiff(ikm/ipr)) ≤ 80 abs(itof(ikm/ipr)-tofid(ikm/ipr)) < 2 noutl(ikm/ipr) ≤ 6 -1100 ≤ vtz ≤ -900 abs(vtx) ≤15 0.40 ≤ missing mass of pK- ≤ 0.62 GeV photon energy ≥ 1.75 GeV abs(missing mass of proton – 1.020) > 15 MeV KK mode ntrk > 1 4 sigma PID ikm/ikp ≠ 0 ithtofhit(ikm/ikp) > 0 prbchi2(ikm/ikp) ≥ 0.02 abs(ytof(ikm/ikp)-tofdiff(ikm/ikp)) ≤ 80 abs(itof(ikm/ikp)-tofid(ikm/ikp)) < 2 noutl(ikm/ikp) ≤ 6 -1100 ≤ vtz ≤ -900 abs(vtx) ≤25 abs(missing mass of proton – Mp) < 0.050 GeV photon energy ≥ 2.00 GeV abs(invm(KpKm) – 1.020) > 10 MeV Event Selections

8. KP Mode : LH2

9. KP Mode : LD2

10. Background Estimation How-to • Generating known reaction components individually. • To select 2 detected particles (K-p or K+K-) reconstructed at the forward spectrometer. • Skimming each component with kinematics filters. • Fitting all components with real data spectrum in various dependence simultaneously to obtain the scaling parameters.

11. Monte Carlo Fitting : LH2 (Kp Mode)

12. Monte Carlo Fitting : LD2 (Kp Mode)

13. KP Mode : LH2

14. KP Mode : LD2

15. KK Mode : LH2

16. Monte Carlo Fitting : LH2 (KK)

17. KK Mode : LH2

18. Background Linearity How-to Global Fitting Factors KKp = 0.0282 KL* = 0.0171 phi = 0.0361 Relative Ratios RKKp = 1. RL* = 0.60638 Rphi = 1.28014

19. Kp Linearity by Photon Energy

20. Contribution K? exchange5 Energy Slices • Both in the Kp(LH2 & LD2) and KK(LH2) detection mode, the results between side-band subtraction and Monte Carlo fitting are consistent. • In the Kp detection mode, there is an energy dependence on the K* exchange in LH2 case; however, no obvious energy dependence in LD2 case. • The results between from Kp and KK detection mode are compatible in higher photon energy region, even if the statistics is lower in KK detection mode. LH2(Kp vs KK)

21. 5 SlicesLH2

22. 5 SlicesLD2

23. 5 SlicesLH2(KK)

24. Comparison betweenLAMP2, CLAS and LEPS

25. Total Cross Section The contact term is absent, since the process γ+n→K0Λ* is the neutral one. Its absence cause the total cross section to become much smaller than that for the proton target. PRELIMINARY PRELIMINARY S.-II Nam, A. Hosaka and H.-C. Kim, Phys. Rev. D 71, 114012.

26. LH2 LD2 Nγ : /np1b/v01/sp8lep/OfficialMacro/runinfo/Photo_llh(d)2.dat by Sumihama-san

27. Summary • In the study of K- decay asymmetry in Λ* helicity frame, if the background linearity is reasonable, the consistency between side-band subtraction and Monte Carlo fitting is good. • Without phi exclusion cut, it is very difficult to study in the KK detection mode; in the Kp detection mode, however, there is no significant difference between the results with and without phi exclusion cut in decay asymmetry study. The results between from Kp and KK detection mode are compatible in higher photon energy region, even if the statistics is lower in KK detection mode. • To make a comparison between different targets, LH2 and LD2, in Kp detection mode, no obvious photon energy dependence was observed in LD2 data. This difference might come from the Λ* photoproduction of neutron. • In Λ* photoproduction, the dominance of K* exchange is proportional to photon energy; in the low energy region, K exchange become important and the contribution from K and K* exchange are equivalent. From our result, it provides a nice bridge between LAMP2 and CLAS experiment, in the high energy, K* exchange significantly dominate the Λ* photoproduction. (Clebsch-Gordon coefficients) • Refer to “Phys. Rev. D 71, 114012“, the absence of the contact term in neutron process leads to the total cross section to become much smaller than that for the proton target. Therefore, from our result, the total cross section of neutron is small, but, not as small as the theoretical prediction, 1/30. On the other hand, our result are not consistent with the theoretical prediction, it is about a factor of 2.

28. Backup Slices LEPS Collaboration Meeting In Taiwan

29. Photon Energy Spectrum LH2(Kp) LH2(KK) LD2(Kp) LD2(KK)

30. KK Mode : LD2

31. KK Mode : LD2

32. KK Mode (W/O Phi exclusion Cut)

33. KK Mode (W/O Phi exclusion Cut)

34. KK Mode (W/O Phi exclusion Cut)

35. Full Photon Energy LH2(Kp vs KK)

36. 2 Energy Slices LH2(Kp vs KK)

37. 3 Energy Slices LH2(Kp vs KK)

38. 4 Energy Slices LH2(Kp vs KK)

39. Full Photon Energy

40. 2 Slices : LH2(Kp)

41. 2 Slices : LD2(Kp)

42. 2 Slices : LH2(KK)

43. 3 Slices : LH2(Kp)

44. 3 Slices : LD2(Kp)

45. 3 Slices : LH2(KK)

46. 4 Slices : LH2(Kp)

47. 4 Slices : LD2(Kp)

48. 4 Slices : LH2(KK)