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

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

3. Super Photon ring-8 GeV SPring-8 8 GeV, 100 mA, e - ring Third-generation synchrotron radiation facility 62 beamlines

4. LEPS Beamline Compton backscattering: 8 GeV e - + UV Laser  E  = 1.5 GeV (tagged) – 2.4 GeV, 3.0 GeV  100 % polarized (direction can be changed easily). Intensity:  2x10 6 /sec for E  max = 2.4 GeV  2x10 5 /sec for E  max = 3.0 GeV 8-GeV e - storage ring Scattering region E  Tagging UV Laser = 351 nm, 257 nm Backscattered photon Backward Compton : Small fraction of the low energy background

5. LEPS spectrometer (forward) TOF Dipole Magnet 0.7 Tesla Target Start CounterDC2DC3 DC1SVTX AC(n=1.03) Charged particle spectrometer with forward acceptance PID from momentum and time-of-flight measurements Photons Momentum [GeV/c] K/  separation K+K+ ++ Mass/Charge [GeV/c 2 ]  P ~6 MeV/c for 1 GeV/c,  TOF ~150 ps,  MASS ~30 MeV/c 2 for 1 GeV/c Kaon

6. Summary of Results from LEPS Backward meson prod. –  PRC 80:052001R(‘09) –   PLB 657:32(‘07)   pentaquark – PRC79:025210(’09) – PRL 91:012002(‘03)  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 – ,   (forward K + ) PRC73:035214(‘06), PRL91:092001(‘03) –   (forward K + ) PRL 97:082003(‘06) –  (1520) PRL 103:012001(‘09), PRL 104:172001(‘10) –   (1385) PRL 102:012501(’09) – Backward  PRC 76:042201(’07) –  (1405),   (1385) (with TPC) PRC 78:035202(‘08)

7.  PRC79:025210(’09) γ n p p n K-K- K+K+  detected Peak at M(nK + ) = 1.524 GeV/c 2 Statistical Significance = 5.2  Blind analysis for new data set with x3 higher statistics is underway Experiment with TPC, LEPS2

8. Selected Topics 1. Backward meson photoproduction

9. Meson photoproduction W ( √s ) = 1.9 – 2.3 GeV cos  cm =  1 ~  0.6 (  cm = 123 o – 180 o ) Resonance term +Born term  M p p, N*,  * s-channel Forward Backward meson exchange resonances Nucleon exchange  p M p p, N*,  * u-channel t-channel  M p p M g NNM g NN*M …. Present data Tree-level diagrams:

10. 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+  *(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-  N)  N,  N,  ’N,  N channels? -

11. Backward Meson Production  Data    ’  Missing Mass 2 (GeV 2 /c 4 ) E  = 2.3 - 2.4 GeV cos  cm =  0.9 Fitting result  p  p x  p  p   p  p   p  p   p  p    ’  Proton (Forward) : measured Meson (Backward): Missing mass u-channel, s-channel N, N* contributions

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

13. 13 Evidence for resonances CLAS : Evidence at W ~ 1850 MeV for S 11 (2090) ELSA : Evidence at W ~ 2070 MeV for D 15 (2068) No for S 11 (2090) PRL 89, 222002(2002) PRL 94, 012004(2005) BES : N* from J/  decay, J/        PRL 97, 062001(2006) N*(1440) N*(1535).. N*(1650).. N*(2070) Particle Data Group P 11 (2100)  N)/  tot = 0.61 in Pitt-ANL model Phys. Rep. 328, 181(2000)  photoproduction

14. 14  ’   Comparison of    ’ and  photoproductions cos  cm =  0.8 ~  0.7 PRC80 052201R (‘10)

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

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

17. 17 Solenoid Magnet Dipole Magnet TPC Buffer Collimator 24Φ Collimator 2 １ Φ Beam TPC

18. Spectrometer TPC  p  K +  +    ∓      -  n

19. The  (1405) lineshape depends on the decay angles at its rest frame? cos    19

20.   0.8< cos   K+ < 1.0 t  

21. Future prospects LEPS2 Project Polarized HD Target

22. New Beamline (LEPS2) 8-GeV e  Detector UV Laser 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 E  resolution Smaller beam size Larger-acceptance detector ~50% of the total budget has been approved. Construction of the beamline &detectors started!! ~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  p/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. BNL-E949 Solenoid Magnet Large Angle Coverage  P/P 10 degree TOF,  E/  x, 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 detector

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. Al wire 2.5cm Polarized HD target In-Beam Cryostat 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

27. W.Roberts PRC73,035215(2006) NK invariant mass (GeV) Polarization Observables in w/o            

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   pentaquark. Backward meson photoproduction – evidence for N* contribution at w=2 GeV? Photoproduction of  (1405) – line-shape analysis,  (1405) vs  *(1385) ratio Future Prospects – LEPS2: higher intensity beam + Large acceptance detector. – Pol. HD target

29. 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)