1. Backward φ photo-production from C and Cu targets at E γ = 1.5 - 2.4 GeV Takahiro Sawada Institute of Physics, Academia Sinica Regular Seminar, AS, 17 May. 2013

2. Introduction Experiment Result & Discussion 2 Summary Table of Contents

3. φ-meson properties in nuclear medium 3 Dropping mass Width broadening Brown & Rho (Brown & Rho scaling) m*/m = 0.8 Hatsuda & Lee (QCD sum-rule) m*/m = 1 - 0.16ρ/ρ 0 (for ρ/ω) m*/m = 1 - 0.03ρ/ρ 0 (for φ) Muroya, Nakamura, Nonaka (Lattice calc.) Klingl, Weise (Effective Chiral Lagrangian) 45MeV for φ (ρ=ρ 0 ) Oset, Ramos (Renormalization of Kaon) 22MeV for φ (ρ=ρ 0 ) Cabrera, Vicente (Renormalization of Kaon) 33MeV for φ (ρ=ρ 0 ) T. Hatsuda, S.H. Lee Phys. Rev. C 46, 34(1992) E. Oset, M.J. Vicente Vacas, H. Toki, A. Ramos Phys.Lett. B508 (2001) 237-242 in the nuclear medium in free space Normalize y ; The strange contents in the nucleon Introduction

4. 4 More works are still required Mass-Shape Measurement CERES/NA45 GSI/HADES CERN-SPS/NA60 RHIC/PHENIX e + e - spectrum in high-energy heavy-ion collisions e + e - spectrum in 2 GeV·A C-C collisions μ + μ - spectrum in 158 GeV·A In-In collisions e + e - spectrum in Au+Au collisions at sNN = 200 GeV No clear evidence for the modification. KEK/E325 e + e - spectrum in 12 GeV p+A βγ < 1.25 Excesses Small FSI Small branching ratio (~10 -4 ) Many backgrounds. JLab/CLAS-g7 No clear evidence e + e - spectrum in E γ < 3.8 GeV Evidence for the dropping mass ? In dilepton decay channel Introduction J-PARC E16 e+e+ e-e- e+e+ e-e-

5. A-dependence Measurement Mass Number A Production Rate of Incoherent φ Photo-Production Photon φ meson Absorption Mass Number A Transparency Ratio σφNσφN σ γN 0.14 mb OZI suppression Expected R φ A T = R φ C / A / A C 12 C Dominant K + K Branching ratio ( 50%) Cancellation of Systematic Errors Nucleon Nucleus R φ A A α Theoretical Calculation Quark model : 13.0 ± 1.5 mb VMD model : 8.2 ± 0.5 mb Expected 1 10 mb 5 Introduction

6. A-dependence @ SPring-8/LEPS +17 -11 σ φN = 35 mb !! Glauber multiple scattering theory T. Ishikawa et al. Phys.Lett. B608 (2005) 215-222 photo-production at E γ = 1.5 – 2.4 GeV φ K + K - = 1.8 GeV/c Li, C, Al, and Cu targets. Mass Number A σ A A 0.72±0.07 Incoherent φ photo- production cross section (arb) Incoherent φ photo-production cross section φ-N interaction cross section 6 Introduction

7. σ φN ( φ-N interaction ) OZI suppression. Analogy to other mesons ( K +, K -, π ± ) φ-N resonance has not been reported. total Total hadronic cross section at a few GeV region σ φN < σ K + N < σ K - N, σ π + N, σ π - N 18 mb 30 mb 30mb 35mb At 2 GeV/c π + p total π + p elastic σ π + p (mb) π + momentum (GeV/c) Resonance π production ? Theoretical Calculation Quark model : 13.0 ± 1.5 mb VMD model : 8.2 ± 0.5 mb 7 Introduction

8. A-dependence @ CLAS/JLab M. H. Wood et al. Phys.Rev.Lett. 105 (2010) 112301 Transparency ratios photo-production at E γ < 3.8 GeV φ e + e - = 2 GeV/c. 2 H, C, Ti, Fe, and Pb targets. e + e - invariant mass (GeV/c 2 ) Mass Number A σ φN = 16-70 mb ρ meson contribution after subtraction from ρ meson contribution 8 Introduction

9. A-dependence @ ANKE-COSY M. Hartmann et al, Phys.Rev. C85 (2012) 035206 2.83 GeV proton beam C, Cu, Ag, and Au targets p φ ; 0.6 - 1.6 GeV/c COSY Transparency ratios φ-N cross section Extracted φ K + K - Momentum of φ meson (GeV/c) Transparency ratio decreases with φ momentum. Momentum of φ meson (GeV/c) (16-70 mb) !? 9 Introduction

10. What does this result mean? Nucleon p φ -meson at slow speed. Nucleon p × φ -meson at fast speed. Absorption Transparent Strongly Modified !?!? Nucleus The verification experiment using Photon-Beam is desired. No Modified ? 10 Introduction

11. SPring-8 (Super Photon ring - 8 GeV) 3rd-generation synchrotron radiation facility 8 GeV electron beam Circumference = 1436 m RF = 508 MHz One-bunch is spread within σ = 12 psec. Beam Current = 100 mA Top-up injection 11 Experiment

12. 12 e 8GeV - 8 GeV Electron Experiment

13. Bremsstrahlung Photon e 8GeV - γ γ γ 13 Experiment

14. Beam Line Map Operational; 54 Planned or Under Construction; 3 The Number of Beamlines April 3, 2012 14 Experiment

15. 15 Backward Compton Scattering Photon e 8GeV - UV-Laser Collide !! γ Experiment

16. 16 Backward Compton Scattering Photon e 8GeV - UV-Laser Collide !! γ Experiment BCS photons Bremsstrahlung photons Photon Energy (GeV) Counts Photon energy measurement Polarized photon beam Forward Detector

17. Laser hutch SR ring Experimental hutch Backward Compton γ -ray Laser light 8 GeV electron Recoil electron Tagging counter Collision 36m 70m LEPS facility Photon energy measurement Polarized photon beam Forward Detector (Laser Electron Photon Experiment at SPring-8) 17 Experiment

18. LEPS Detector Setup Forward Spectrometer TOF : RF signal - TOF wall, Δ t = ~150 ps Momentum : Δp ~ 6 MeV/c for 1 GeV/c K Acceptance : Hori ±20 o, Vert ±10 o TPC 20 o < θ < 160 o Δ p/p ~0.1 Δφ ~0.04 rad Standard Setupw/ TPC 18 Experiment

19. Time Projection Chamber (TPC) 600mm E (180 V/cm) B (2 T) beam Charged Particle Target Drift ~ 5 cm/μsec γ Ionization Avalanche Measurement 3-dimensional Tracking Detector Track Curvature Momentum Ionization Energy Loss (dE/dx) Particle Identification (π/K/p) Avalanche Positions + Drift Times 3-D Trajectory of the Charged Particle (Gas-filled Cylindrical Chamber + MWPC) Large Acceptance Small Amount of Material 19 Experiment

20. Difficulty in This Experiment TPC has the best performance for the tracks emitted in the sideward direction. We have improved the analysis procedure to measure the tracks emitted in the forward direction. Collider ExperimentCosmic Ray Experiment Fixed Target Experiment TPC Beam Target 20 Experiment

21. 01234(m) Collimator Buffer Star t Dipole Magnet TOF Counters DC1 DC2DC3 TPC Solenoid Magnet Up Stream e + e - Veto Counter Aerogel Cherenkov Counter ^ Trigger Scintillator Counter (TPC-FWD) Trigger Scintillator (TPC-SIDE) γ Collimator Target Start Dipole Magnet TOF Counters DC1 DC2DC3 Aerogel Cherenkov Counter ^ SVTX Counter γ Target Detector Acceptance Previous Experiment This Experiment Acceptance Forward + 20 o < θ < 160 o Acceptance Hori ±20 o Vert ±10 o (w/ TPC) (Standard Setup) 21 Experiment

22. Detection Modes for φ mesons γ γ K K p ± ± γ K K p + - TOF Counters TPC Drift Chambers K K + - TOF Counters Drift Chambers γ Previous Experiment This Experiment p K K + - Momentum of φ meson in LAB system Fast Slow (Standard Setup) (w/ TPC) TPC Angle of φ meson in CM system Forward Backward 22 Experiment

23. φ Experiment with Nuclear Targets @Spring-8/LEPS This experimentPrevious experiment PeriodSep.- Dec. in 2004Nov. in 2001 Beam1.5-2.4 GeV photons TargetsC, Cu, and CH 2 Li, C, Al, and Cu Reactionφ K + K - Main Detectors TPC + LEPS spectrometer LEPS spectrometer φ momentump φ = 0.3-2.0 GeV/c p φ = 1.0-2.2 GeV/c (Average 1.8 GeV/c) 23 Experiment

24. K + K - Invariant Mass 0.6< p φ <1.3 (GeV/c) in tpc K P spK mode ± ± χ 2 /ndf = 149/102 N φ = 178±16 C target DATA Fit result φK + K - (determined by the MC simulation) background (2nd-order polynomial) Fit range ; from 2m K ± (0.987) to 1.2 GeV/c 2 Summary Table Contamination from miss-PID (π,p) K + K - Invariant Mass (GeV/c 2 ) 2 m K ± (0.987 GeV/c 2 ) Constraint Counts (/2MeV/c 2 ) 24 Result & Discussion

25. Transparency Ratio This experiment (C and Cu) Previous experiment (Li, C, Al, and Cu) Transparency ratio decreases with φ momentum. Here, the production rate of φ mesons Transparency Ratio Momentum of φ meson (GeV/c) 25 Result & Discussion

26. Model Calculation Nuclear density distribution: Woods-Saxon photon φ meson σ γN = 0.14mb σ φN nucleus nucleon here, φ φ Glauber Approximation The model calculation ; Transparency Ratio σ φN, Systematic errors from angle effect in tpc K P spK mode ± ± in tpc K + K - P, tpc K + K - spP modes at σ φN = 10mb ~ 0.2% ~ 0.9% We calculated as the emission angle =0. 26 Result & Discussion

27. σ φN = 21.7 mb +8.7 -6.2 χ 2 /ndf = 6.95 / 3 ( χ 2 prob.= 7 % ) Transparency Ratio p φ (GeV/c) Blue: w/o KN Red: w/ Strong KN σφNσφN Not So Good. Momentum Dependent ? 27 Result & Discussion

28. Momentum Dependent ?? σ φN = α (const.) σ φN = α p φ σ φN = α p φ 2 Momentum Independent 28 Result & Discussion

29. σ φN (Momentum Dependent) σ φN = α(const.) σ φN = α p φ χ 2 /ndf = 6.95 / 3 ( χ 2 prob.= 7 % ) χ 2 /ndf = 2.77 / 3 (χ 2 prob. = 43%) σ φN = α p φ 2 χ 2 /ndf = 1.32 / 3 (χ 2 prob. = 72 %) Transparency Ratio p φ (GeV/c) Blue: w/o KN Red: w/ Strong KN More Appropriate 29 Result & Discussion

30. σ φN (Momentum Dependent) σ φN = α p φ 2 χ 2 /ndf = 1.32 / 3 (χ 2 prob. = 72 %) Transparency Ratio p φ (GeV/c) σ φN = 6.8 mb +3.4 -2.3 σ φN = 88.1 mb +43.7 -29.8 At lower p φ (0.5 GeV/c) At higher p φ (1.8 GeV/c) Consistent with the theoretically predicted value in free space. Unexplainable value !!! α = 27.2 mb/(GeV/c) 2 +13.5 -9.2 30 Result & Discussion

31. Discussion This suggests that the cause of the transparency ratio reduction at higher p φ is not the φ-N interaction. If so, Why ? What's happening ? 31 Result & Discussion

32. Discussion Propagation Photon φ meson Absorption σφNσφN σ γN Nucleon Nucleus Production The number of φ-mesons produced on nucleon is (almost) proportional to the target mass number A. The flux of φ-mesons is decreased by the σ φN. Fixed Measured Unexplainable In higher p φ, (= Diffractive) φ photo-production might have a strong A-dependence. 32 Result & Discussion

33. Discussion R φ Cu Transparency Ratio = R φ C / A Cu / A C Decreasing ? Increasing ? ( R A ; Production Rate) φ 33 Data-taking with many kinds of target nuclei. Improvement of the statistical precision. For further study Measurement of the absolute cross section for each target (not the ratio) Measurement at higher p φ. ( Decreasing ) Result & Discussion

34. Related Topic 34 W.C. Chang et al. Phys.Lett., B684:6–10, 2010. E γ (GeV) [ (dσ d /dt) / (2*dσ p /dt) ] t=tmin Transparency Ratio Transparency ratio for the deuteron at forward angles A significant reduction Some effect other than nuclear density ? φ photo-production from the deuteron target @ SPring-8/LEPS

35. Summary We have confirmed that the transparency ratio decreases with p φ. The reduction of the transparency ratio shown in the high p φ region suggests that σ φN increases as p φ 2. a diffractive φ photo-production might have a strong A- dependence. For further study, we point out the importance of the measurement of the absolute cross section for each target, of the improvement the statistical precision, of the data-taking with many kinds of target nuclei, and of the measurement until more higher p φ. 35 Summary

36. 36 Thank you for your attention !!