Photoproduction of      and     on the proton for comparing ūu and d̄d productions at LEPS/SPring-8 May/16/2016 RCNP, Osaka University, Japan Hideki Kohri 1

Electron storage ring 8 GeV electron beam Diameter ≈457 m RF 508 MHz 1‐bunch spread is within σ ＝ 12 psec ． Beam Current = 100 mA 120 km distant from Osaka Super Photon ring ‐ ８ GeV 2

SPring-8 beamline map LEPS 3

LEPS facility LEPS experiment started in 2000 b) Laser hutch a) SPring-8 SR ring c) Experimental hutch Inverse Compton  -ray Laser light 8 GeV electron Recoil electron Tagging counter Collision Energy spectrum of BCS photons Bremsstrahlung Backward-Compton scattering 36m 70m SSD + Sc hodoscope ScFi + Sc hodoscope Beam intensity < 2.5 x 10 6 for E  = GeV (355 nm laser) < 3.0 x 10 5 for E  = GeV (257 nm laser) 4

 LEPS detector setup 1m1m TOF wall MWDC 2 MWDC 3 MWDC 1 Dipole Magnet (0.7 T) Target Silicon Vertex Detector Aerogel Cerenkov (n=1.03) Start counter LEPS detector was optimized to detect  meson decaying to K + K - at forward angles for removing e + e - BG also removed pions 5

 New experimental setup for high momentum  TOF wall MWDC 2 MWDC 3 MWDC 1 Dipole Magnet (0.7 T) Target Silicon Vertex Detector Start counter No Aerogel Cherenkov counter Plastic counter for vetoing e + e - was used e-e- e+e+ 6

7 High momentum  data Momentum (GeV) Counts Mass / Charge (GeV/c 2 ) p p p d t       K+K+ e - e + Momentum range of previous experiments K+K+ d

Missing mass of p( ,  )X p( ,  + )X p( ,  - )X E  = GeV 0.7<cos   <1 8

ūu and d̄d productions Same acceptance Simultaneous measurements Same proton target ūu production is precisely compared with d̄d production by the γp→ π - Δ ++ and π + Δ 0 reactions 9     p p   

SAPHIR data published in 2005 C. Wu et al. (SAPHIR collaboration) Eur. Phys. Jour. A 23 (2005) 317     -> p  -      (  +  0 )/  (  -  ++ ) (+0)(+0)  (  -  ++ )   (?) E  (GeV) Clebsch-Gordan coefficients  * favors  +  0 channel 10 N * -> 3  -  ++ : 1  +  0  * -> 3  -  ++ : 4  +  0 Resonance effect t-channel LEPS energy No d  /dcos 

Physics motivation of  reactions at E  = GeV Low energy  E  =1.5 GeV Missing resonance search s- channel High energy  E  =3.0 GeV Precision of isospin rule is checked t- channel     p p p p          N*N* Isospin=1 Isospin=2  (  +  0 )/  (  -  ++ ) = 1/3  (  +  0 )/  (  -  ++ ) = 4/3  (  +  0 )/  (  -  ++ ) = 1/3  (  +  0 )/  (  -  ++ ) = 3  11

High momentum  data taken in 2007 p( ,  + )X p( ,  - )X E  = GeV 0.7<cos   <1 12

Preliminary differential cross sections for     and     p( ,  - )  ++ p( ,  + )  0 E  (GeV) d  /dcos  (  b) Preliminary 0.7<cos  < <cos  < <cos  < <cos  < <cos  < 1 0.7<cos  < <cos  < <cos  < <cos  < <cos  < 1 13

Preliminary ratio  (  +  0 )/  (  -  ++ ) 1/3 is expected from isospin=1 exchange in the t-channel Preliminary 14 (d̄d production / ūu production ) d̄d production is enhanced or ūu production is suppressed.

If interference between  and  exists, the ratio may be changed from 1/3 15 t-channel  or  Interference ? The interference between  and  exchanges may change the ratio of 1/3.

Isospin=2 exotic meson exchange in the t-channel may increase the ratio if it exists t-channel 16

Comparison between LEPS and SLAC data 17  (  +  0 )/  (  -  ++ ) Momentum transfer t (GeV 2 /c 2 ) 0.7 < cos   < 1 LEPS data E  = GeV Preliminary SLAC data E  = 16 GeV A.M Boyarski et al. PRL 25 (1970) 695 One conclusion Isospin=2 exchange contributes to the large cross section ratio. Momentum transfer t (GeV 2 /c 2 )

Another explanation Proton charge distribution Pion cloud model   (ud̄) may enhance     prodution(d̄d production)  Larger          Bare proton Pion cloud (ud) 18 (d̄d / ūu ) Drell-Yan experiment PRD 64 (2001) d̄ / ū

Photon beam asymmetry using linearly polarized  beams 0.9<cos   <1 0.8<cos   < <cos   =0.8  -  ++  +  0 Azimuthal Angle  (deg.) Nv-Nh Nv+Nh Nv-Nh Nv+Nh 0.7<cos   < <cos   < <cos   <1 E  = GeV E  = GeV E  = GeV E  = GeV 19

Preliminary photon beam asymmetry for  p ->     and  p ->     reactions  exchange  exchange Preliminary 20

 N →    X  N →   X Missing mass (GeV) We are taking new data using LD 2 target from Dec. of 2015 Counts nn pp          New

22 Same acceptance Simultaneous measurements Same neutron target     n n   ūu and d̄d productions by using neutron target

Refrigerators used for polarized HD target SPring-8 RCNP RCNP -> SPring-8 We obtained from ORSAY GRAAL 23

Polarization degree of proton in HD Aging HD Year P H (%) 40% -- 30% 18% 42% 44+-1% NMR Calibration data at T=4.2 K, B=0.9 Tesla Polarization is grown up by ~2000 times NMR After aging HD for 3 months HH We carried out the 6th aging of HD in the beginning of

Relaxation time of H polarization in the SPring-8 experimental condition Polarization degree (%) Time (day) Aging HD Year T H (days) T=0.3 K B=0.9 Tesla T H = days In

SPring-8 beamline map LEPS2 26 LEPS

LEPS 2 experiment hutch was constructed in 2011 August LEPS2 experiment hutch Experiment hall of SPring-8 27

BNL-E 949 spectrometer was transported to SPring- 8 SPring-8 LEPS2 experiment hutch 28

LEPS2 solenoid spectrometer system We will start commissioning runs in this year 2.22 m  TPC DC  counter RPC TOP Magnet (BNL-E949) B=1 T Magnet (BNL-E949) B=1 T 29 ☆ Acceptance 5 – 120° (charged particle) 40 – 110° (photon) ☆ Momentum measurement - sideway (30– 120°) TPC Δp/p ~ 0.04 (1 GeV/c) - forward (5 – 40°) DC Δp/p ~ 0.01 (1 GeV/c) ☆ Particle Identification 3σ separation up to 2.7 GeV/c - sideway (50 – 120°) RPC (TOF) - middle (30 – 50°) AC, RPC - forward (5 – 30°) TOP, RPC(<11°)

Summary We have been carrying out photoproduction experiments at E  = GeV at the LEPS facility since We newly took high momentum  data at E  = GeV. Precise comparison between ūu and d̄d productions is possible in  p ->      and      reactions  Preliminary cross section ratio  (  +  0 )/  (  -  ++ ) is found to be larger than 1/3 expected from the I=1 exchange in the t-channel. Preliminary photon beam asymmetry is typically found to be negative for     and positive for      reaction. We are taking data for  n ->     and     reactions now. After this experiment, we plan to install a polarized HD target. We are developing a large acceptance LEPS2 spectrometer for the near future experiments at SPring-8. 30

LEPS/LEPS2 collaboration RCNP, Osaka University, Ibaraki, Osaka , Japan Research Center for Electron Photon Science, Tohoku University, Sendai, Miyagi , Japan Kyoto University, Kyoto , Japan Pusan National University, Busan , Republic of Korea Konan University, Kobe, Hyogo , Japan XFEL Project Head Office, RIKEN 1-1, Koto, Sayo, Hyogo , Japan Academia Sinica, Taipei 11529, Taiwan Japan Synchrotron Radiation Research Institute, Sayo, Hyogo , Japan Japan Atomic Energy Agency, Kizugawa, Kyoto , Japan Nagoya University, Nagoya, Aichi , Japan Ohio University, Athens, OH 45701, USA Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki , Japan Yamagata University, Yamagata , Japan Chiba University, Chiba , Japan Wakayama Medical College, Wakayama, Wakayama , Japan Miyazaki University, Miyazaki , Japan National Defense Academy in Japan, Yokosuka, Kanagawa , Japan Tokyo Institute of Technology, Tokyo , Japan University of Saskatchewan, Saskatoon, SK S7N 5E2, Canada University of Minnesota, Minneapolis, MN 55455, USA Gifu University, Gifu , Japan Michigan State University, East Lansing, MI 48824, USA University of Connecticut, Storrs, CT , USA Joint Institute for Nuclear Research, RU Dubna, Russia National Chung Cheng University, Taiwan 31

Thank you 32

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 (     )/  (     ) ratio expected from Clebsch-Gordan coefficients I=1 (  or  ) exchange in the t-channel should be dominant at forward  angles. Deviation from 1/3 might suggest I=2 exotic meson exchange. Dominant 34