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Takashi NAKANO (RCNP, Osaka University) for the LEPS collaboration

Highlights and Prospects from LEPS and LEPS2. LEPS. Takashi NAKANO (RCNP, Osaka University) for the LEPS collaboration. Bryons’10 @ Osaka, December 9 th , 2010. LEPS Collaboration. Research Center for Nuclear Physics, Osaka University ： D.S. Ahn, M. Fujiwara, T. Hotta, Y. Kato,

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Takashi NAKANO (RCNP, Osaka University) for the LEPS collaboration

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  1. Highlights and Prospects from LEPS and LEPS2 LEPS Takashi NAKANO (RCNP, Osaka University) for the LEPS collaboration Bryons’10 @ Osaka, December 9th, 2010

  2. LEPS Collaboration Research Center for Nuclear Physics, Osaka University：D.S. Ahn, M. Fujiwara, T. Hotta, Y. Kato, H. Kohri, Y. Maeda, T. Mibe, N. Muramatsu, T. Nakano, S.Y. Ryu, T. Sawada, M. Yosoi, T. Yorita Department of Physics, Pusan National University：J.K. Ahn School of Physics, Seoul National University：H.C. Bhang Department of Physics, Konan University：H. Akimune Japan Atomic Energy Research Institute / SPring-8：Y. Asano Institute of Physics, Academia Sinica：W.C. Chang, J.Y. Chen Japan Synchrotron Radiation Research Institute (JASRI) / SPring-8： S. Date', H. Ejiri, N. Kumagai, Y. Ohashi, H. Ohkuma, H. Toyokawa Department of Physics and Astronomy, Ohio University：K. Hicks Department of Physics, Kyoto University： M. Niiyama, K. Imai, H. Fujimura, M. Miyabe, T. Tsunemi Department of Physics, Chiba University：H. Kawai, T. Ooba, Y. Shiino Wakayama Medical University：S. Makino Department of Physics and Astrophysics, Nagoya University：S. Fukui Department of Physics, Yamagata University：T. Iwata Department of Physics, Osaka University：S. Ajimura, K. Horie, M. Nomachi, A. Sakaguchi, S. Shimizu, Y. Sugaya Department of Physics and Engineering Physics, University of Saskatchewan：C. Rangacharyulu Laboratory of Nuclear Science, Tohoku University：T. Ishikawa, H. Shimizu Department of Applied Physics, Miyazaki University：T. Matsuda, Y. Toi Institute for Protein Research, Osaka University：M. Yoshimura National Defense Academy in Japan：T. Matsumura RIKEN： Y. Nakatsugawa Department of Education, Gifu University： M. Sumihama,

  3. Laser Electron Photon beamline at SPring-8

  4. Backward-Compton Scattered Photon • 8 GeV electrons in SPring-8 + 351nm Ar laser (3.5eV） maximum 2.4 GeV photon • Laser Power ~6 W  Photon Flux ~1 Mcps • E measured by tagging a recoil electron  E>1.5 GeV, E ~10 MeV • Laser linear polarization 95-100% ⇒ Highly polarized  beam Linear Polarization of  beam PWO measurement tagged photon energy [GeV] photon energy [MeV]

  5. Setup of LEPS Detectors Only FWD spectrometer ±20°x ±10° 1.5

  6. g E // B Setup of LEPS Detectors 1.5 Polarized HD target will be ready soon. Talk by YOSOI (P4)

  7. TOF SVTX DC1 AC(n=1.03) Photons Target Dipole Magnet 0.7 Tesla Start Counter DC2 DC3 PID in LEPSSpectrometer K/p separation K+ p+ Momentum [GeV/c] Mass/Charge [GeV/c2] P~6 MeV/c for 1 GeV/c TOF~150 ps MASS~30 MeV/c2 for 1 GeV/c Kaon

  8. High linear polarization • Flat energy spectrum • Good forward acceptance • Good p/K separation Features of LEPS facility • Linear polarization can be used to study spin-parity of exchanged particle in t-channel. • Forward spectrometer is suitable for studying reactions near production threshold. • Tagged photon energy region is close to ss thresholds.

  9. f(1020)

  10. q g r, w _ q N Diffractive Photoproduction of vector meson • Vector Meson Dominance • Meson Exchange • Pomeron Exchange _ qq = r, w, f ... Dominant at low energies g r, w f (~ss) Slowly increasing with energy N uud

  11. Scattering amplitude Pomeron 2nd Pomeron Total crosssection

  12. fphotoproduction near production threshold Titov, Lee, Toki Phys.Rev C59(1999) 2993 Data from: SLAC('73), Bonn(’74),DESY(’78) P2 : 2nd pomeron ~ 0+ glueball (Nakano, Toki (1998)) Decay asymmetry helps to disentangle relative contributions ⊥ ⊥

  13. Polarization observables with linearly polarized photon f meson rest frame K+ eg Decay Plane // g natural parity exchange (-1)J (Pomeron, Scalar Glueball, Scalar mesons) Polarization vector of g K- eg Decay Planeg unnatural parity exchange -(-1)J (Pseudoscalar mesons p,h) K+ Decay angular distribution of f meson Relative contributions from natural, unnatural parity exchanges

  14. Differential cross section at t=-|t|min Phys. Rev. Lett. 95, 182001 (2005) Bump is confirmed by CLAS. Talk by DEY (EM1)

  15. Decay angular distribution 2.173<Eg<2.373 GeV W 1.973<Eg<2.173 GeV W f cosq f-F f+F F Curves are fit to the data. No energy dependence, except for f distribution. Natural parity exchange is dominant.

  16. Bump structures around 2 GeV in some reactions PRL95,182001 (2005) PRL104,172001 (2010)

  17. (1116)

  18. 0,- L LD2 data LH2 data (1405) 0(1385) - (1385) L 0 (1405) (1385) (1520) (1520) N(, K+) GeV/c2 p(, K+) GeV/c2 Acceptance of close to 1. Identification of Hyperon From p/d in LEPS: Missing Mass of K+ Y  spectrometer K+ p/d

  19. contact term For gauge invariance. Born Diagrams for Hyperon Photoproduction s-channel u-channel t-channel

  20. Photon Beam Asymmetry L(1116) S0(1193) • K+K*-exchange by M. Guidal. • Isobar + Regge by T. Mart and C. Bennhold. • Gent isobar model by T. Corthals Larger contribution from t-channel K* exchange. M. Sumihama et al. (LEPS Collaboration), PRC 73, 035214 (2006)

  21. Wess–Zumino–Witten term S. Ozaki, H. Naghiro, A. Hosaka, PLB 665, 178 (2008) SU(3)

  22. (1520)

  23. Photoproduction of Λ(1520) from p/d N. Muramatsu et al. (LEPS Collaboration), PRL 103, 012001 (2009)

  24. A Large Isospin Asymmetry in L* Production S.i. Nam, A. Hosaka, and H.-Ch. Kim,Phys. Rev. D, 71, 114012 (2005) A. Hosaka, Workshop of “Challenge to New Exotic Hadrons with Heavy Quarks”.

  25. Backward mesonproductions M g p p p, N*,,, in high energy region gMpp

  26. Missing mass spectra • p  p x w/r Eg = 2.3 - 2.4 GeV cosQcm = -1 ~ -0.9 Data Fitting result h’ f h p0 4p 3p 2p Missing Mass2 (GeV2/c4)

  27. Differential cross sections for h photoproduction Jlab/CLAS data Bonn/ELSA data SAID -partial-wave analysis Eta-MAID - isobar model LEPS data I = ½, small J, strong coupling to h, heavy  may contain large ss component

  28. Q+(1530) uudds

  29. Quasi-free production of Q+ and L(1520) detected K- K+ Eg=1.5~2.4 GeV K+ K- g g Q+ L(1520) n p n p p n p n Data was taken in 2002-2003. spectator • Both reactions are quasi-free processes. • Fermi-motion should be corrected. • Existence of a spectator nucleon characterize both reactions.

  30. Minimum Momentum Spectator Approximation K- detected tagged Spectator nucleon K+ γ vpn d at rest p n Nucleon from decay or scattering We know 4 momentum of pn system Mpn and ptot |pCM|and vpn Direction of pCM is assumed so that the spectator can have the minimum momentum for given |pCM| and vCM.

  31. Results of L(1520) analysis Simple (g,K+) missing mass: No correction on Fermi motion effect. Proton is assumed to be stopped in the Lab system.

  32. Results of L(1520) analysis pK- invariant mass with MMSA: Fermi motion effect corrected. Simple (g,K+) missing mass: No correction on Fermi motion effect. Structure with a width less than 30 MeV/c2 requires a physics process or fluctuation. The total cross section is ~1 mb, which is consistent with the LAMP2 measurements. D(-2lnL) =55.1 for Dndf=2 7.1s

  33. Results of Q+ analysis Simple (g,K-) missing mass: No correction on Fermi motion effect. Neutron is assumed to be stopped in the Lab system.

  34. Results of Q+ analysis nK+ invariant mass with MMSA: Fermi motion effect corrected. Simple (g,K-) missing mass: No correction on Fermi motion effect. Reflection of L(1520) PRC 79, 025210 (2009) “We DO NOT estimate the statistical significance by counting the number of events above background level” D(-2lnL) =31.1 for Dndf=2 5.2s

  35. Next step LARGE fluctuations are required if the peak is not real. High statistics data was already collected in 2006-2007 with the same experimental setup. Blind analysis is under way to check the Θ+ peak The result will tell us if the peak structure is due to statistical fluctuations or not unambiguously.

  36. LEPS2

  37. LEPS2 Project at SPring-8 High intensity： Multi (ex. 4) laser injection w/ large aperture beam-line & Laser beam shaping ~10 7 photons/s（LEPS ~10 6 ） High energy：Re-injection of X-ray from undulator E < 7.5GeV (LEPS < 3GeV) Backward Compton Scattering 8 GeV electron Recoil electron (Tagging) 30mlong line （LEPS 7.8m) Laser or re-injected X-ray GeV g-ray Better divergencebeam collimated photon beam Different focus points for multi CW laser injection Inside building Outside building Detail will be given by YOSOI (P4) Large 4p spectrometer based on BNL-E949 detector system. Better resolutions are expected. New DAQ system will be adopted. Experimental hutch

  38. E949 Solenoid Magnet size: Φ5m×3.5m weight: ~400 t Field: 1.0 T (1.1 MW at 4400 A) Target cell g CFRP SSD Target and Vertex detector Main Detector Setup

  39. Construction of LEPS2 has been started! Please join us!!

  40. Summary • LEPS is a Backward Compton gamma beam facility at SPring-8. GeV g beam with high polarization is available. • LEPS detector has a good forward angle acceptance which is complimentary to the CLAS acceptance. • A bump structure is observed in f photo-production near threshold. • Strong isospin dependence was observed in L(1520) photo-production. • Evidence for new baryon resonance in h photo-production, which may contain ss component. • Q+ peak was observed in the nK+ invariant mass at 1.53 GeV/c2. New data set with 3 times more statistics was taken. Blind analysis is under way. • 7. LEPS2 project is ongoing: 10 times stronger beam & 4p coverage.

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