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Hadron physics with meson photoproduction at LEPS/SPring-8

MESON 2010 CRACOW, POLAND 12 JUNE 2010. Hadron physics with meson photoproduction at LEPS/SPring-8. Tomoaki Hotta (RCNP, Osaka University) for LEPS Collaboration. Outline. LEPS ( L aser- E lectron P hoton at S Pring-8) Experiment Brief summary of the recent results

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Hadron physics with meson photoproduction at LEPS/SPring-8

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  1. MESON 2010 CRACOW, POLAND 12 JUNE 2010 Hadron physics with meson photoproduction at LEPS/SPring-8 TomoakiHotta(RCNP, Osaka University) for LEPS Collaboration

  2. Outline • LEPS (Laser-Electron Photon at SPring-8) Experiment • Brief summary of the recent results • Some Selected topics • Backward meson photoproduction • Photoproduction of L(1405) • Future prospects: LEPS2

  3. Super Photonring-8GeVSPring-8 • 8 GeV, 100 mA, e- ring • Third-generation synchrotron radiation facility • 62 beamlines

  4. LEPS Beamline Eg Tagging Scattering region Compton backscattering: 8 GeV e- + UV Laser • Eg = 1.5 GeV (tagged) – 2.4 GeV, 3.0 GeV ~100 % polarized (direction can be changed easily). Intensity: ~ 2x106/sec for Egmax = 2.4 GeV ~ 2x105/sec for Egmax = 3.0 GeV Backscattered photon UV Laser l = 351 nm, 257 nm 8-GeV e- storage ring Backward Compton : Small fraction of the low energy background

  5. LEPS spectrometer (forward) Charged particle spectrometer with forward acceptance PID from momentum and time-of-flight measurements K/p separation TOF SVTX DC1 K+ p+ AC(n=1.03) Momentum [GeV/c] Photons Target Dipole Magnet 0.7 Tesla Start Counter DC2 DC3 Mass/Charge [GeV/c2] P ~6 MeV/c for 1 GeV/c, TOF ~150 ps, MASS ~30 MeV/c2 for 1 GeV/c Kaon

  6. Summary of Results from LEPS • Hyperon production • L, S0 (forward K+) PRC73:035214(‘06), PRL91:092001(‘03) • S- (forward K+) • PRL 97:082003(‘06) • L(1520) • PRL 103:012001(‘09), • PRL 104:172001(‘10) • S*-(1385) • PRL 102:012501(’09) • Backward L • PRC 76:042201(’07) • L(1405), S0(1385) (with TPC) • PRC 78:035202(‘08) • Backward meson prod. • hPRC 80:052001R(‘09) • p0PLB 657:32(‘07) • Q+ pentaquark • PRC79:025210(’09) • PRL 91:012002(‘03) • f photoproduction • Proton target PRL95:182001(‘05) • Nuclear targets PLB608:215(’05) • D target (coherent) PLB658:209(‘08) • D target (indoherent) PLB684:6 (‘10)

  7. Q+ detected K- • PRC79:025210(’09) K+ γ Q+ n n p p Peak at M(nK+) = 1.524 GeV/c2 Statistical Significance = 5.2 s Blind analysis for new data setwith x3 higher statistics is underway Experiment with TPC, LEPS2

  8. Selected Topics 1. Backward meson photoproduction

  9. Meson photoproduction Resonance term +Born term Tree-level diagrams: t-channel u-channel s-channel g M g p M p, N*, D* p p p M gNNM gNN*M …. meson exchange Nucleon exchange resonances g M Forward Backward p p p, N*, D* Present data • W ( √s ) = 1.9 – 2.3 GeV • cosQcm = -1 ~ -0.6 (Qcm = 123o – 180o)

  10. Motivation: Baryon resonances Problems in the constituent quark models • Mass-order-reverse problem for the lowest excited baryons. • S11(1535) uud(L=1) ½- should be the lowest • P11(1440) uud(n=1) ½+ • L*(1405) uud(L=1) ½- •  introducing additional qq to solve the problem. • Missing baryon resonances • The number of predicted states is much less than observed. •  coupling to (non-pN) rN, hN, h’N, wN channels? -

  11. Backward Meson Production • p  p x w/r Eg = 2.3 - 2.4 GeV cosQcm = -1 ~ -0.9 Proton (Forward) : measured Meson (Backward): Missing mass u-channel, s-channel N, N* contributions Data Fitting result h’ f gp  p p p gp  p p p p gp  p p p p p gp  p p0/h/h’/w h p0 Missing Mass2 (GeV2/c4)

  12. Results: Differential cross sections for hphotoproduction Jlab/CLAS data PRL89:222002(2002) Bonn/ELSA data PRL94:012004(2005) SAID -partial-wave analysis Eta-MAID - isobar model LEPS data Bump-like structure is seen above W=2.0 GeV

  13. Evidence for resonances h photoproduction CLAS : Evidence at W~ 1850 MeV for S11(2090) ELSA : Evidence at W ~ 2070 MeV for D15(2068) No for S11(2090) PRL 89, 222002(2002) PRL 94, 012004(2005) BES : N* from J/y decay, J/y  N*N  p NN PRL 97, 062001(2006) N*(1440) N*(1535).. N*(1650).. N*(2070) Particle Data Group P11(2100) G(hN)/Gtot = 0.61 in Pitt-ANL model Phys. Rep. 328, 181(2000)

  14. Comparison of p0, h, h’ andw photoproductions h h’ w p0 cosQcm = -0.8 ~ -0.7 PRC80 052201R (‘10)

  15. Selected Topics 2. Photoproduction of L(1405)

  16. g E // B LEPS detector setup with TPC 1.5

  17. TPC Solenoid Magnet Buffer Collimator 24Φ Collimator 2１Φ Dipole Magnet TPC Beam 17

  18. g p  K+ L(1405)  K+S p∓  K+ p+p-n Spectrometer TPC

  19. cosq*p cosq*p The L(1405) lineshape depends on the decay angles at its rest frame? 19

  20. 0.8< cosq*K+< 1.0 S(1385) S(1385) t L(1405) L(1405)

  21. Future prospects LEPS2 Project Polarized HD Target

  22. New Beamline (LEPS2) 8-GeV e- UV Laser Detector • Smaller (1/4) • beam divergence • Multiple (x4) laser injection • 8W 16W / laser tube • improved optics • Much higher intensity beam • ~ x 10 or higher • Better tagged Eg resolution • Smaller beam size • Larger-acceptance detector ~50% of the total budget has been approved. Construction of the beamline &detectors started!!

  23. Design Concept of the Main detector • Momentum resolution at forward angle Dp/p~1%. •  Good reaction tag. • Large and smooth acceptance azimuthally  Decay and polarization. • Detection of decay product down to lower momentum 100 MeV/c • Detection of neutral particle (Photon)

  24. LEPS2 detector • BNL-E949 Solenoid Magnet • Large Angle Coverage • DP/P < 1.4% qlab > 10 degree • TOF, DE/Dx , TOP, AC for PID • Symmetric acceptance for positive • and negative particles • Collaboration with Belle and J-PARC, RIKEN • RPC, TOPcounter, DSSD, GEM-TPC… • Detailed design, R&D in progress

  25. LEPS2 Schedule • 2010 - 2011 • Construction of Beamline • R&D of the detectors and DAQ • Construction of Experimental Hall • Transporting E949 magnet+detectors • 2012 • Beam comissioning • Construction of main detector • 2013 • Start LEPS2 experiment

  26. 2.5cm Al wire Polarized HD target Polarize HD at 10 mK, 17 T at RCNP  Transport to LEPS site Longstanding R&D at Syracuse, LEGS/BNL, and Orsay. Polarized successfully. Polarization measurement underway In-Beam Cryostat

  27. Polarization Observables in W.Roberts PRC73,035215(2006) w/o Q+ Q+(1/2+) Q+(1/2-) NK invariant mass (GeV)

  28. Summary • LEPS experiment • Linearly polarized real photon beam (~3 GeV) • Forward charged-particle spectrometer. • TPC+Solenoid, surrounding the target • Meson photproduction • Production and decay of baryon resonances, Hyperon resonances, and exotic Q+ pentaquark. • Backward meson photoproduction • evidence for N* contribution at w=2 GeV? • Photoproduction of L(1405) • line-shape analysis, L(1405) vs S*(1385) ratio • Future Prospects • LEPS2: higher intensity beam + Large acceptance detector. • Pol. HD target

  29. LEPS/LEPS2 Collaboration Nagoya Univ. Yamagata Univ. Miyazaki Univ. National Defense Academy Tokyo Institute of Technology Academia Sinica (Taiwan) Ohio Univ. (USA) Pusan National Univ. (Korea) Seoul National Univ. (Korea) Univ. of Saskatchewan (Canada) JINR Dubna (Russia) Univ. of Connecticut (USA) National Chung Cheng Univ. (Taiwan) RCNP / Osaka Univ. Osaka Univ. Tohoku Univ. JASRI / SPring-8 Kyoto Univ. Tohoku Univ. JAEA Chiba Univ. Konan Univ. Wakayama Med. College RIKEN KEK Univ. of Tokyo

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