MESON 2010 CRACOW POLAND 12 JUNE 2010 Hadron

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: LEPS 2

Super Photon ring-8 Ge. V SPring-8 • 8 Ge. V, 100 m. A, e - ring • Third-generation synchrotron radiation facility • 62 beamlines

LEPS Beamline Scattering region 8 -Ge. V e- storage ring Eg Tagging Backscattered photon UV Laser l = 351 nm, 257 nm Compton backscattering: 8 Ge. V e- + UV Laser Eg = 1. 5 Ge. V (tagged) – 2. 4 Ge. V, 3. 0 Ge. V ~100 % polarized (direction can be changed easily). Intensity: ~ 2 x 106/sec for Egmax = 2. 4 Ge. V ~ 2 x 105/sec for Egmax = 3. 0 Ge. V 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 DC 1 K/p separation TOF Momentum [Ge. V/c] AC(n=1. 03) p+ Photons K+ Target Dipole Magnet Start Counter 　0. 7 Tesla DC 2 DC 3 Mass/Charge [Ge. V/c 2] P ~6 Me. V/c for 1 Ge. V/c, TOF ~150 ps, MASS ~30 Me. V/c 2 for 1 Ge. V/c Kaon

Summary of Results from LEPS • Backward meson prod. – h PRC 80: 052001 R(‘ 09) – p 0 PLB 657: 32(‘ 07) • Q+ pentaquark – PRC 79: 025210(’ 09) – PRL 91: 012002(‘ 03) • f photoproduction – Proton target PRL 95: 182001(‘ 05) – Nuclear targets PLB 608: 215(’ 05) – D target (coherent) PLB 658: 209(‘ 08) – D target (indoherent) PLB 684: 6 (‘ 10) • Hyperon production – L, S 0 (forward K+) PRC 73: 035214(‘ 06), PRL 91: 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), S 0(1385) (with TPC) PRC 78: 035202(‘ 08)

Q+ detected K- PRC 79: 025210(’ 09) K+ γ n p Q+ p n Peak at M(n. K+) = 1. 524 Ge. V/c 2 Statistical Significance = 5. 2 Blind analysis for new data set with x 3 higher statistics is underway Experiment with TPC, LEPS 2

Selected Topics 1. Backward meson photoproduction

Meson photoproduction Tree-level diagrams: g t-channel M g s-channel M g Resonance term +Born term u-channel p M p p meson exchange p 　　　　 p p, N*, D* resonances Forward p, N*, D* p g. NNM g. NN*M M …. Nucleon exchange Backward Present data ü W ( √s ) = 1. 9 – 2. 3 Ge. V ücos. Qcm = -1 ~ -0. 6 (Qcm = 123 o – 180 o)

Motivation: Baryon resonances Problems in the constituent quark models • Mass-order-reverse problem for the lowest excited baryons. S 11(1535) uud(L=1) ½- should be the lowest P 11(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-p. N) r. N, h’N, w. N 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 p gp p p 0/h/h’/w Data Fitting result p 0 w/r Eg = 2. 3 - 2. 4 Ge. V cos. Qcm = -1 ~ -0. 9 h’ f h Missing Mass 2 (Ge. V 2/c 4)

Results: Differential cross sections for h photoproduction LEPS data Jlab/CLAS data PRL 89: 222002(2002) Bonn/ELSA data PRL 94: 012004(2005) SAID -partial-wave analysis Eta-MAID - isobar model Bump-like structure is seen above W=2. 0 Ge. V

Evidence for resonances h photoproduction CLAS : Evidence at W ~ 1850 Me. V for S 11(2090) PRL 89, 222002(2002) ELSA : Evidence at W ~ 2070 Me. V for D 15(2068) PRL 94, 012004(2005) No for S 11(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 P 11(2100) G(h. N)/Gtot = 0. 61 in Pitt-ANL model Phys. Rep. 328, 181(2000) 13

Comparison of p 0, h, h’ and w photoproductions h h’ cos. Qcm = -0. 8 ~ -0. 7 PRC 80 052201 R (‘ 10) w p 0 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 Beam 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) t L(1405)

Future prospects LEPS 2 Project Polarized HD Target

New Beamline (LEPS 2) 8 -Ge. V e- UV Laser Detector • Smaller (1/4) • Multiple (x 4) laser injection beam divergence • 8 W 16 W / 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 Me. V/c • Detection of neutral particle (Photon)

LEPS 2 detector • BNL-E 949 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

LEPS 2 Schedule • 2010 - 2011 – – Construction of Beamline R&D of the detectors and DAQ Construction of Experimental Hall Transporting E 949 magnet+detectors • 2012 – Beam comissioning – Construction of main detector • 2013 – Start LEPS 2 experiment

Polarized HD target Polarize HD at 10 m. K, 17 T at RCNP Transport to LEPS site Longstanding R&D at Syracuse, LEGS/BNL, and Orsay. Polarized successfully. Polarization measurement underway 2. 5 cm In-Beam Cryostat Al wire

Polarization Observables in W. Roberts PRC 73, 035215(2006) w/o Q+ Q+(1/2+) Q+(1/2 -) NK invariant mass (Ge. V)

Summary • LEPS experiment – – Linearly polarized real photon beam (~3 Ge. V) 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 Ge. V? • Photoproduction of L(1405) – line-shape analysis, L(1405) vs S*(1385) ratio • Future Prospects – LEPS 2: higher intensity beam + Large acceptance detector. – Pol. HD target

LEPS/LEPS 2 Collaboration RCNP / 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)