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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 (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 Super Photon ring-8 GeV SPring-8 • 8 GeV, 100 mA, e- ring • Third-generation synchrotron radiation facility • 62 beamlines LEPS Beamline Scattering region Compton Scatterin g BM1 BM2 CR2 Tagging counter Eg Tagging (SSD + Plastic Scint.) Backscattered photon LEP Laser 8-GeV e- storage ring UV Laser l = 351 nm, 257 nm 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 Backward Compton : Small fraction of the low energy background LEPS spectrometer (forward) Charged particle spectrometer with forward acceptance PID from momentum and time-of-flight measurements SVTX DC1 K/p separation TOF Momentum [GeV/c] AC(n=1.03) p+ Photons K+ 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 Summary of Results from LEPS • Backward meson prod. – h PRC 80:052001R(‘09) – p0 PLB 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) • 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) Q+ detected K- PRC79:025210(’09) K+ γ n p Q+ p n Peak at M(nK+) = 1.524 GeV/c2 Statistical Significance = 5.2 Blind analysis for new data set with x3 higher statistics is underway Experiment with TPC, LEPS2 Selected Topics 1. Backward meson photoproduction Meson photoproduction Tree-level diagrams: g t-channel M g s-channel g M M p, N*, D* p p Resonance term +Born term u-channel p meson exchange p p, N*, D* resonances Forward p p gNNM gNN*M M …. Nucleon exchange Backward Present data W ( √s ) = 1.9 – 2.3 GeV cosQcm = -1 ~ -0.6 (Qcm = 123o – 180o) 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? Backward Meson Production gp p x Proton (Forward) : measured Meson (Backward): Missing mass u-channel, s-channel N, N* contributions gp p p p gp p p p p gp p p p p p gp p p0/h/h’/w Data Fitting result p0 w/r Eg = 2.3 - 2.4 GeV cosQcm = -1 ~ -0.9 h’ f h Missing Mass2 (GeV2/c4) Results: Differential cross sections for h photoproduction Jlab/CLAS data LEPS data PRL89:222002(2002) Bonn/ELSA data PRL94:012004(2005) SAID -partial-wave analysis Eta-MAID - isobar model Bump-like structure is seen above W=2.0 GeV Evidence for resonances h photoproduction CLAS : Evidence at W ~ 1850 MeV for S11(2090) PRL 89, 222002(2002) ELSA : Evidence at W ~ 2070 MeV for D15(2068) PRL 94, 012004(2005) No for S11(2090) BES : N* from J/y decay, J/y N*N p NN N*(1440) N*(2070) PRL 97, 062001(2006) N*(1535).. N*(1650).. Particle Data Group P11(2100) G(hN)/Gtot = 0.61 in Pitt-ANL model Phys. Rep. 328, 181(2000) 13 Comparison of p0, h, h’ and w photoproductions h h’ cosQcm = -0.8 ~ -0.7 PRC80 052201R (‘10) w p0 14 Selected Topics 2. Photoproduction of L(1405) LEPS detector setup with TPC 1.5 g E // B TPC Solenoid Magnet Buffer Collimator 24Φ Collimator 21Φ Dipole Magnet TPC 17 g p K+ L(1405) K+S p∓ K+ p+ p- n Spectrometer TPC cosq*p The L(1405) lineshape depends on the decay angles at its rest frame? cosq*p 19 0.8< cosq*K+< 1.0 S(1385) S(1385) t L(1405) L(1405) Future prospects LEPS2 Project Polarized HD Target New Beamline (LEPS2) 8-GeV e- UV Laser Detector • Smaller (1/4) • Multiple (x4) laser injection beam divergence • 8W 16W / laser tube • improved optics • Much higher intensity beam ~ x 10 or higher • Larger-acceptance detector • Better tagged Eg resolution • Smaller beam size ~50% of the total budget has been approved. Construction of the beamline &detectors started!! 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) 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 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 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 2.5cm In-Beam Cryostat Al wire Polarization Observables in K +Y* + K +Q g +N K+K +N f + N non - res. W.Roberts PRC73,035215(2006) w/o Q+ T Q+(1/2+) BT CZZ BT CZX Q+(1/2-) NK invariant mass (GeV) 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 LEPS/LEPS2 Collaboration 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 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)