1. Incoherent φ photo-production from deuteron at SPring-8/LEPS M. Miyabe 博士論文審査５人委員会

2. contents Physics motivation Experiment Analysis Results Conclusion and discussion summary

3. Vector Meson Photo-production ● Vector Meson Dominance ● Meson Exchange ● Pomeron Exchange  N   N  (~ss) q _q_q _ qq =  Dominant at low energies Slowly increasing with energy Almost constant around threshold uud

4.  p  p  p  p M.A. Pichowsky and T.-S. H. Lee PRD 56, 1644 (1997) Prediction from Pomeron exchange Prediction from meson exchange Data from: LAMP2('83), DESY('76), SLAC('73), CERN('82), FNAL('79,'82), ZEUS('95,'96) Prediction : dominant contribution form pseudo scalar meson exchange near threshold Vector Meson Photo-production

5. Titov, Lee, Toki Phys.Rev C59(1999) 2993 Data from: SLAC('73), Bonn(’74),DESY(’78) Natural parity exchange Unnatural parity exchange Important to distinguish natural parity exchanges from unnatural ones P 2 : 2 nd pomeron ~ 0 + glueball (Nakano, Toki (1998))  =0 degree)  photo-production near threshold

6. Polarization observables with linearly polarized photon Decay Plane //  natural parity exchange (-1) J (Pomeron, Scalar mesons) Polarization vector of  K+K+ K+K+ K-K- In  meson rest frame Decay Plane  unnatural parity exchange -(-1) J (Pseudo scalar mesons  )   Relative contributions from natural, unnatural parity exchanges Decay angular distribution of  meson

7.  K+ K+K+ K-K-  p’  meson rest frame (Gottfried-Jackson(GJ) frame)  K+ K+K+ K-K-   pol Production plane z Decay plane z-axis  K+ -  pol    direction of linear polarization Decay angular distribution of  meson

8. Decay angular distribution ● W 0,W 1,W 2 are parameterized by the 9 spin density matrix elements.     Re(    )                    Im(    ) and  Im(    ) Unpolarized part Polarized part K.Schilling et al. Nucl. Phys. B15(1970) 408

9. Spin density matrix elements 1-dimensional projections Relations to standard definition

10.  distribution Prediction by A. Titov (PRC,2003) -- Pure natural parity exchange Pure unnatural parity exchange 0   P, glueball, , f 2 ’   p

11. 11 LEPS result (proton) Peak structure around 2GeV. Natural parity exchange is dominant → 0 + glueball ? Pseudo scalar meson exchange is not negligible. T. Mibe, et al. nucl-ex/0506015

12. Explore the exotic process Is the bump structure candidate of 2 nd Pomeron (glueball)? – Only decay asymmetry can explain using Pseudo scalar exchange, But for cross section enhancement, Need to natural parity exchange comparable effect from Pseudo scalar exchange process. – Detailed study for pseudo scalar π-η exchange is important. To study incoherent photo-production from deuteron is unique tool.

13. 2005/09/21HAW0513 φ photo-production of Deuteron 1.Coherent production – Interact with deuteron itself. 2.Incoherent production – Interact with proton or neutron in deuteron.

14. 2005/09/21HAW0514 Coherent production Deuteron is iso-scalar target – Iso-vector π exchange is forbidden. Pure natural parity exchange except for η-exchange process.

15. LEPS result Differential cross sectionDecay asymmetry Differential cross section at t=tmin shows Decreasing with energy. Dashed line shows theoretical calcuration. Decay asymmetry shows natural parity exchange is dominant

16. From coherent result Differential cross section – Increase with energy – Not only Pomeron and η-exchange Decay asymmetry – Pure natural-parity exchange – η-exchange is weak? Additional natural parity process is required!

17. Incoherent production Due to isospin effect, – g πnn = - g πpp → destructive – g ηnn = g ηpp → constructive π-η interference effect  Detail Information for unnatural (π/η) exchange process 2005/09/21HAW0517 g (π, η)NN g φγ (π, η) π,η φγ NN

18. Differential cross section for as a function of energy and angle. For πη interference effect, neutron cross section decrease at low energy and forward angle.

19. Decay asymmetry as a function of energy and η-exchange strength Decay asymmetry Σ φ =2ρ 3 Eγ=2 GeV Large difference for decay asymmetry cause large η-exchange process

20. Aim of this thesis Differential cross section for incoherent process – (π 、 η)-interference Decay asymmetry for γ+N→φ+N – η-exchange process magnitude  Extract clearly quasi-free γ+N→φ+N event  Explore the exotic pomeron exchange in the Bump structure.

21. Nuclear transparency ratio T=σ A /(A*σ N ) (=P out ) Mass number dependence is larger than theoretical calculation. Large σ φN in nuclear medium. – How about duteron case?

22. EXPERIMENT

23. The LEPS beamline 

24. Linearly polarized Photon Backward Compton scattering by using UV laser light Intensity (typ.) : 2.5 * 10 6 cps Tagging Region : 1.5 GeV< E  < 2.4 GeV Linear Polarization : 95 % at 2.4 GeV E  (Tagger) (GeV) E  (GeV) Counts Linear polarization

25. Charged particle spectrometer 1m TOF wall MWDC 2 MWDC 3 MWDC 1 Dipole Magnet (0.7 T) Liquid Hydrogen Target 50mm-long (2000 Dec.-2001June) 150mm-long (2002May-July) Start counter Silicon Vertex Detector Aerogel Cerenkov (n=1.03) 

26. Summary of data taking ● Trigger condition : TAG*UpVeto*STA*AC*TOF ● Run period I (50mm-long LH 2 ) 2000,Dec. – 2001, June II (150mm-long LH 2 )2002,May - 2002.July III (150mm-long LD2) 2002,July – 2003 Feb, Apr-Jun ● Total number of trigger I 1.83*10 8 trigger (~50% Horizontal, ~50% Vertical pol.) II 1.71*10 8 trigger III 4.64*10 8 trigger

27. ANALYSIS

28. φ Event selection Number of track ≧ 1 K +, K - Particle Identification cut (PID) Decay in flight cut (DIF) Vertex cut Tagger Invariant Mass K+K- cut Missing Mass cut

29. Particle identification and decay in flight cut Kaon identification is 4σ Consistency of TOF hit position – Difference of y-position of TOF ≦ 80mm – Difference TOF slat number ≦ 1 Number of outlier – Noutl ≦ 6 χ2 probability – Prob(χ2) ≧ 0.02 Decay in flight cut

30. Vertex cut -1120. < Vertex z < 880. -30< Vertex(x,y) < 30

31. Invariant mass K+K- Fit with Gaussian convoluted breit-weigner Resolution~1.5MeV Cut point for invariant mass is 10MeV

32. Missing Mass cut Missing mass distribution forγ + p → φ X (MMp) From the fermi motion effect Cut for MMp at LD 2 set to 80 MeV

33. Summary of φ selection

34. Procedure analysis for quasi-free like Incoherent γ+N→φ+N production LEPS spectrometer has designed for forward φ→K + K - event – Exclusive γ+n→φ+n event can’t accept.  Precisely analysis for possible reactions is required. Coherent process Final State Interaction(FSI) Fermi motion effect Fortunately, exclusive γ+p→φ+p has a small acceptance.

35. Energy Definitions For cross section For decay asymmetry

36. Minimum momentum spectator approxmation γ n p n p φ n p P CM n p γ P KK E KK Pγ Eγ P miss E miss In the lab system, the missing momentum Become minimum at the direction is anti-parallel to photon The momentum of pn system as

37. P min characteristic coherent process – P min ~ +0.15 – Dominant P min ≧ 0.1 Quasi-free process make peak around zero. Other inelastic reactions distribute large negative value.

38. Monte-Carlo simulation for P min coherent process – Dominant > 0.1GeV Quasi-free process clear symmetric peak around zero. around P min ~ 0.1GeV cut point for quasi-free process P min distribution in MC

39. Extract quasi-free incoherent process P min distribution Real with MC Contamination from coherent as a function of P min cut Coherent contamination is large in High energy region about 10% at P min ≦ 0.09 in this estimation

40. Validity check for Quasi-free process cut |P min | ≦ 0.9 slopeDifferential cross section P min cut dependence is flat |P min |=0.9 at Slope and cross section except for 2-Highest energy bin. In E8, about 10% fluctuation from the tighter cut.

41. Introduce the effective photon energy P min strongly correlated to z-component of fermi momentum inside deuteron. P min could be used for estimating Fermi momenta of target nucleons.  Total center of mass energy s of KKN system Pmin vs. Fermi momentum z

42. Conversion Eγ eff from Eγ Effective photon energy Eγ eff as s is the center of mass total energy of KKN system. Resolution for Eγ is improved. (~50%) Eγ resolution

43. Conversion to effective photon flux Photon flux ω γ for each Eγ as ω γ (Eγ)=ε Tag (Eγ) ＊ N tag ε Tag (Eγ) : Tagger efficiency N tag : corrected tagger scalar count In nucleon at rest frame, At one specific Eγ eff, it depends on some Eγ which spread over because of fermi motion. Conversion ratio from each Eγ bin is calculated using Monte-Carlo.

44. Conversion ratio original EminEmaxFrac 1.5731.673.31905E+12 1.6731.873.32266E+12 1.7731.873.36441E+12 1.8731.973.39824E+12 1.9732.073.50882E+12 2.0732.173.53101E+12 2.1732.273.62225E+12 2.2732.373.53687E+12 2.3732.473.18670E+12 Eγ eff = 1.973-2.073 0.005 0.26 0.56 0.20 New Frac (1.973-2.073) = 0.005*0.364E+12 + ・・・ +0.20*0.53E12 Eγ

45. Estimate the Final state interaction In the threshold energy, momentum of outgoing nucleon is small. – Final state interaction? Strength of FSI is enhanced in small relative momentum p and n. (similar kinematics in coherent) n p n φ γ p

46. Monte Carlo simulation Real data fitted with Monte Carlo simulation coherent, incoherent and FSI. FSI contribution is very weak at all energy bin. Missing Mass distribution MM D Black :real, red coherent green: incoherent, blue: FSI

47. P-N relative momentum fit P-n relative momentum fitted FSI. χ2/ndf distribution as a function of FSI strength Weak FSI effect become better χ2 weak  FSI effect is negligible small

48. Background subtraction Assuming the Background shape is non-resonant KK event. Estimate the number of background with side band region. Non-resonant K + K - invariant mass

49. RESULT

50. Differential cross section t dependence. Fitted function as dσ/dt = C*exp(-b*t) Fitted result of slope parameter b As a function of Eγ eff Not monotonic behavior of slope, Slope b = 3.74 +/- 0.12 (free proton b=3.38+/-0.23)

51. Differential cross section at t=t min dσ/dt at (θ=0) with Constant slope b=3.74 Differential cross section at forward angle. Not clearly seen the bump like structure.

52. Differential cross section with tighter P min cut Not monotonic behavior of slope, Slope b = 3.45 +/- 0.13 (free proton b=3.38+/-0.23) dσ/dt at (θ=0) with b=3.45 t dependence P min ≦ 50 Cross section decrease at E1~E3

53. 3-particle KKp mode dσ/dt at (θ=0) with Constant slope b=3.38 Cross section for Exclusive K + K - p event. Very limited statistic. The bump like structure was seen same as free proton

54. Decay angular distribution ρ 1~5 as a function of EγDecay angluar distribution

55. Conclusion and Discussion Differential cross section at t=t min – About 30% reduction from free proton Not a simply nuclear density effect since deuteron is loosely bounded. – φ→ω conversion? Red : incoherent γN→φN Black: free proton Lower Histgram T d = (dσ/dt) N /2*(dσ/dt) p

56. Differential cross section in KKp mode Similar degree of reduction such as incoherent process – π-η interference is small Red : exclusive KKp event Black: free proton Lower Histgram T d = (dσ/dt) KKp /(dσ/dt) free p

57. Spin density matrix element ρ 3 N is little bit higher than free proton. Theoretical prediction of ρ 3 n is 0.25~0.30. – ρ 3 N is 0.23~0.25 good agreement Small difference ρ 3 p and ρ 3 n – η-exchange is small ρ 3 as a function of Eγ ρ3ρ3 Red : γ+N→φ+N Black : γ+p→φ+p

58. Tighter P min cut Differential cross section at t=t min Red : incoherent γN→φN Black: free proton Red : γ+N→φ+N Black : γ+p→φ+p ρ 3 as a function of Eγ Decrease in Highest energy region

59. Summary Differential cross section for incoherent φ photo-production shows a significant reduction from free proton – Some effect other than nuclear density is necessary (ex, φ-ω conversion). From analysis for exclusive KKp event, – π-η interference is small. Decay asymmetry ρ 3 is similar with free proton one – η exchange component is weak. Bump structure around Eγ= 2GeV for γ+p→φ+p → a new natural parity candidate (glueball). P min ≦ 90 MeV(50MeV) selection cut occurs a large systematic err in highest energy bin. More detailed study is needed.

61. Backup figures

62. Eγ vs. Eγ(n) Eγ Eγ(n)

63. Spin density matrix HorzVert

64. Spin density matrix

65. ρ Horz, VertHorz+Vert

66. Spin density matrix element

67. Vert Horz

68. P min dependence slopeDifferential cross section

69. Photon flux

71. Comparison to LEPS result

72. Tagger cut

73. Coherent contamination

74. Lambda(1520)

75. Non-resonant BG

76. 2005/09/21HAW0576 Experiment at Spring-8 8GeV electron storage ring Harima Hyogo

78. Liquid hydrogen target 150mm

79. Drift Chamber calibration Depth of the multi hit TDC ~3 (before 8) High Voltage value of sense wire is large. Threshold for discri- amp is low. – Noisy level is high

80. t 0 calibration Large fluctuation in TDC offset value t 0. – Every 10 run calibration. DC-t 0 run dependence run tdc

81. xt-calibration X drift = c 1 t+c 2 t 2 +c 3 t 3 +c 4 Correct the origin-point Calcurate parameters when resolution and efficiency are down

82. Result of calibration Number of outlier Χ^2 probability LH2(short) LH2(long)