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Backward φ photo-production from C and Cu targets at E γ = 1.5 - 2.4 GeV

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

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Backward φ photo-production from C and Cu targets at E γ = 1.5 - 2.4 GeV

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

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

  3. Introduction φ-meson properties in nuclear medium Dropping mass Brown & Rho (Brown & Rho scaling) m*/m = 0.8 Hatsuda & Lee (QCD sum-rule) m*/m = 1 - 0.16ρ/ρ0 (for ρ/ω) m*/m = 1 - 0.03ρ/ρ0 (for φ) y ; The strange contents in the nucleon Muroya, Nakamura , Nonaka(Lattice calc.) T. Hatsuda, S.H. Lee Phys. Rev. C 46, 34(1992) Width broadening Klingl, Weise (Effective Chiral Lagrangian) 45MeV for φ (ρ=ρ0) in free space in the nuclear medium Oset , Ramos (Renormalization of Kaon) 22MeV for φ (ρ=ρ0) Normalize Cabrera, Vicente (Renormalization of Kaon) 33MeV for φ (ρ=ρ0) E. Oset, M.J. Vicente Vacas, H. Toki, A. Ramos Phys.Lett. B508 (2001) 237-242

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

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

  6. Introduction A-dependence @ SPring-8/LEPS photo-production at Eγ= 1.5 – 2.4 GeV φ → K+K- < pφ > = 1.8 GeV/c Li, C, Al, and Cu targets. Incoherent φphoto-production cross section σA ∝ A0.72±0.07 Glauber multiple scattering theory Incoherent φphoto-production cross section (arb) φ-Ninteraction cross section +17 -11 σφN = 35 mb !! Mass Number A T. Ishikawa et al.Phys.Lett. B608 (2005) 215-222

  7. Introduction σφN ( φ-N interaction ) Theoretical Calculation Quark model : 13.0 ± 1.5 mb VMD model : 8.2 ± 0.5 mb Analogy to other mesons ( K+, K-,π±) ・ OZI suppression. Resonance ・ φ-N resonance has not been reported. πproduction ・ Total hadronic cross section at a few GeV region π+p total σπ+p (mb) π+p elastic ・ At 2 GeV/c π+ momentum(GeV/c) σφN < σK+N < σK-N , σπ+N ,σπ-N ? 18 mb 30 mb 30mb 35mb ln2(s/s0) + ・・・ total

  8. Introduction A-dependence @ CLAS/JLab photo-production at Eγ < 3.8 GeV φ → e+e- ρ meson contribution < pφ> = 2 GeV/c . after subtraction from ρ meson contribution 2H, C, Ti, Fe, and Pb targets. Transparency ratios Mass Number A → 　σφN= 16-70 mb e+e- invariant mass (GeV/c2) • M. H. Wood et al.Phys.Rev.Lett. 105 (2010) 112301

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

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

  11. Experiment 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

  12. Experiment 8 GeV Electron - e 8GeV

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

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

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

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

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

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

  19. Experiment Time Projection Chamber (TPC) 3-dimensional Tracking Detector (Gas-filled Cylindrical Chamber + MWPC) γ ・ Large Acceptance ・ Small Amount of Material 600mm ~ 5cm/μsec ② Drift ③ Avalanche ④ Measurement ① Ionization ・ Avalanche Positions + Drift Times →3-D Trajectory of the Charged Particle ・ Track Curvature →Momentum  beam Target ・ Ionization Energy Loss (dE/dx) → Particle Identification (π/K/p) Charged Particle E (180 V/cm) B (2 T)

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

  21. Experiment Detector Acceptance TOF Counters Dipole Magnet Previous Experiment ^ Aerogel Cherenkov (Standard Setup) Counter Start Counter γ Acceptance Hori ±20o Vert ±10o Target DC1 DC2 DC3 TOF Counters This Experiment Dipole Magnet SVTX Solenoid Magnet ^ Aerogel Cherenkov (w/ TPC) TPC Counter Start Buffer Counter Collimator γ Acceptance Forward + 20o< θ < 160o Target Collimator Up Stream e+e- Veto Counter Trigger Scintillator DC1 (TPC-SIDE) DC2 DC3 Trigger Scintillator (TPC-FWD) 0 1 2 3 4 (m)

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

  23. Experiment φExperiment with Nuclear Targets @Spring-8/LEPS

  24. Result & Discussion K+ K-Invariant Mass ーDATA C target ーFit result ± ± in tpc K P spK mode ーφ→K+K- (determined by the MC simulation) 0.6< pφ<1.3 (GeV/c) Counts (/2MeV/c2) ーbackground (2nd-order polynomial) Nφ= 178±16 Fit range ; from 2mK±(0.987) to 1.2 GeV/c2 χ2/ndf = 149/102 Summary Table K+K- Invariant Mass (GeV/c2) Constraint 2 mK± (0.987 GeV/c2) Contamination from miss-PID (π,p)

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

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

  27. Result & Discussion σφN +8.7 Blue: w/o KN Red: w/ Strong KN σφN = 21.7 mb -6.2 χ2/ndf = 6.95 / 3 ( χ2 prob.= 7 % ) Transparency Ratio Not So Good. Momentum Dependent ? pφ(GeV/c)

  28. Result & Discussion Momentum Independent σφN = α (const.) Momentum Dependent ?? σφN= α・pφ σφN = α・pφ2

  29. Result & Discussion σφN(Momentum Dependent) σφN = α(const.) σφN= α・pφ σφN = α・pφ2 Blue: w/o KN Red: w/ Strong KN Transparency Ratio χ2/ndf = 6.95 / 3 ( χ2 prob.= 7 % ) χ2/ndf = 2.77 / 3 (χ2 prob. = 43%) χ2/ndf = 1.32 / 3 (χ2 prob. = 72 %) pφ(GeV/c) More Appropriate

  30. Result & Discussion σφN(Momentum Dependent) σφN = α・pφ2 +13.5 α= 27.2 mb/(GeV/c)2 -9.2 At lower pφ(0.5 GeV/c) +3.4 σφN= 6.8 mb Transparency Ratio -2.3 Consistent with the theoretically predicted value in free space. χ2/ndf = 1.32 / 3 (χ2 prob. = 72 %) At higher pφ(1.8 GeV/c) pφ(GeV/c) +43.7 σφN= 88.1 mb -29.8 Unexplainable value!!!

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

  32. Result & Discussion Discussion Fixed ●Production φ meson The number of φ-mesons produced on nucleon is (almost) proportional to the target mass number A. Absorption Photon σφN In higher pφ , (= Diffractive) φphoto-production might havea strong A-dependence. σγN Nucleon ● Propagation Nucleus The flux of φ-mesons is decreased by the σφN . Unexplainable Measured

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

  34. Related Topic φphoto-production from the deuteron target @ SPring-8/LEPS Transparency ratio for the deuteron atforward angles → A significant reduction [ (dσd/dt) / (2*dσp/dt) ]t=tmin Transparency Ratio Eγ (GeV) W.C. Chang et al. Phys.Lett., B684:6–10, 2010. Some effect other than nuclear density ?

  35. Summary Summary ・ We have confirmed that the transparency ratio decreases with pφ. ・ The reduction of the transparency ratio shown in the high pφregion suggests that ・ σφN increases as pφ2. ・ 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 pφ .

  36. Thank you for your attention !!

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