Status of LEPS Mizuki Sumihama For LEPS collaboration Gifu university New hadron  Introduction of LEPS  Previous work  Update (new setup)  Status of present work

2 Super Photon ring-8 GeV SPring-8 8 GeV electron Intensity is 100 mA. Circumference: 1436 m 62 beamlines LEPS

3 b) Laser hutch a) SPring-8 SR ring c) Experimental hutch Inverse Compton  -ray Laser light 8 GeV electron Recoil electron Tagging counter Collision Laser Electron Photon beam Energy spectrum LEP Bremsstrahlung Backward-Compton scattering 36m 70m

4 Cross section(Energy spectrum) Linear Polarization Polarization of photon beam is calculated by using photon energy event by event. Linearly polarized photons 351 nm 257 nm tagged 351 nm 257 nm tagged

5 LEPS spectrometer – forward acceptance  5 1m1m TOF wall MWDC 2 MWDC 3 MWDC 1 Dipole Magnet (0.7 T) Liquid Hydrogen Target (15 cm thick ) Start counter Silicon Vertex Detector Aerogel Cherenkov (n=1.03) ± 10 o in y ± 20 o in x

Particle identification 6 Time resolution ~120ps Momentum resolution ~5(14) MeV for 1(2) GeV/c Kaon

Previous works at LEPS Linearly polarized photon beam E  = 1.5 – 2.4 GeV / W p target = 1.9 – 2.3 GeV Target Liquid hydrogen / deuteron / Li, Al, Cu, C Channels hyperon :  p  K + , K +  0, K + , K + ,     n  K +  -, K +    0,  meson :  p   p,  d   d,  N   N,  A   A   p   p,  p    p,   (petaquark) :  n(C) ,  n(d)  K -  +  Missing baryon resonances (N*,  *), ~2000MeV  Exotic hadron,    Time projection chamber

Advantage of photon beam  N     N,  N,  N,  ’N,  N,  N, KY, KY* …, simultaneously Polarization observables –linearly polarized photon, parity filter polarized target under construction Isospin filter :  ’  I=0,  N* only  I=1,  N* and  * Strangeness channel (ss-bar) K , K , K  *, K  *,  N,  N, K -   8 Multi-channel analysis

9 Many *, or ** states Table of baryon excited states –PDG assessment 1700 MeV LEPS range ***, or **** states

10 Backward meson photoproduction  Data    ’  Missing Mass 2 (GeV 2 /c 4 ) E  = GeV cos  cm =  0.9 Fitting result  p  p x Background  p  p   p  p   p  p      Look at   p,  p,  ’p, and  p, simultaneously

11 Differential cross sections d  /d  vs. √s Orsay(PR 164, 1623(1967)) DESY(PRL 20, 230(1968)) cos  cm  LEPS cos  cm      1232 ~1600 ~1720 ~  ~1660 ~1720 ~ ? New data Preliminary 00  3 GeV

12 Photon asymmetries vs. cos  cm LEPS data, other data 70’s Strong angular dependence SAID MAID2007 NPB104, 253(76), NPB154, 492(79) 00  3 GeV

Resonances strongly coupled to .  S(1535) --- contain ss-bar  P(1710/1720)  ? 13 S(1535) P(1720/1710) Higher mass resonance?  photoproduction 

14 Differential cross sections d  /d  vs. W LEPS data SAID -partial-wave analysis Wide structure is seen above W=2.0 GeV Jlab/CLAS data Bonn/ELSA data 

15  ’   Comparison of    ’ and  photoproductions cos  cm =  0.8 ~  0.7     ’   3 GeV  

16 d  /du vs. √ s at small |u| 0.0<u<0.02  0.1<u<0.0 Daresbury data, PLB72,144(1977) √s (GeV) d  /du LEPS ? Smaller than Regge trajectory s -3.0 s -3.9   3 GeV

17 d  /dt  photoproduction at forward angles E  (GeV)  3 GeV T. Mibe, PRL 95, (2005)

Measurement of γp  K + Λ(1405) and K + Σ 0 (1385) M. Niiyama et al, Phys.Rev.C78:035202,2008 target : H 2 (CH 2 – C) GeV GeV Λ(1405) 0.43   Σ 0 (1385) 0.80   d  /d  Remarkable decreasing  different production mechanism or/and internal structure? Decay particles are detected by time-projection chamber  LH2

Study of  + (  d  K - K + np) PRC 79, T.Nakano et al., (2009) Higher statistics (3 times) in data taken in Still under analysis. 19 ++  n  K -  +  K - K + n

20  E  max = 2.4 GeV  3.0 GeV Two laser injection Energy dependence at higher energy with fwd spec. and LH2 and LD2 in 2007 ~  New Time-projection chamber E γ dependence of Λ(1405),  (1385)  Liquid hydrogen target was used. Total luminosity : 3 times larger than previous work  Neutron counter new channel with n in 2010~ Upgrade (new setup) of LEPS

 beam Forward spectrometer p / K /   (1405)  Upgrade of detectors  p  K + x  p  p x Missing mass Time-projection chamber (TPC) target cos  cm = ~ 0.6 – 1.0  p  K +  *  p  p  Neutron counter

A typical efficiency is 20%.  d(pn      n  n  K -  +  K - K + n  p  K s  +  K s K + n  n   n  n  K -  +  K - K + n  p  K s  +  K s K + n Neutron detector Just behind the TOF wall – 1.6 m (y) x 3.8 m (x) – Cover acceptance of fwd spectrometer By K. Hick, Ohio univ.

Setup of time projection chamber with LH2/LD2 23

Time projection chamber 24 Pad planefull view event display x-y resolution : mm z resolution : ~700mm Measurement of  p  K + Λ(1405) and K + Σ 0 (1385)  p   p,  p,  p.. PID with TPC p π+π+ π-π- K-K-

Analysis Spectrum of Σ 0 (1385) M(pπ - ) in the TPC Λ(1116) peak : ± GeV/c 2 missing mass spectrum of γ(p,K + ) X Λ(1116) Σ 0 (1192) Λ(1520) Σ 0 (1385) γ p  K + Σ 0 (1385)  K + Λ(1116) π 0  K + pπ - π 0 TPCspectrometer VERY PRELIMINARY Λ(1116) By Y. Nakatsugawa

Analysis Spectrum of Λ(1405) γ p  K + Λ(1405)  K + Σ ± π  K + n π + π － spectrometer TPC ± VERY PRELIMINARY missing mass spectrum of γ(p,K + ) X Λ(1405) Λ(1520) By Y. Nakatsugawa

27 Summary     photoproduction  strong angular / energy dependence   missing resonance?  Λ(1405) / Σ 0 (1385) /  (1520) photoproduction remarkable energy dependence   + under analysis with 3 times statistics. under analysis  Upgrade of LEPS E  max = 2.4 GeV  3.0 GeV with LH2 and LD2 in 2007 ~ New Time-projection counter with LH2 E γ dependence of Λ(1405),  (1385) Liquid hydrogen target was used. Total luminosity : 3 times larger than previous work Neutron counter new channel with n

28 Recent publication: Measurement of Spin-Density Matrix Elements for  -Meson Photoproduction from Protons and Deuterons Near Threshold. W.C. Chang et al., Phys.Rev.C82:015205,2010. Near-Threshold Λ(1520) Production by the γ p + Λ(1520) Reaction at Forward K + Angles, H. Kohri, et al., Phys. Rev. Lett. 104, (2010)Phys. Rev. Lett. 104, (2010) Measurement of the incoherent γd→φpn photoproduction near threshold, W.C. Chang, M. Miyabe, T. Nakano, et al., Phys.Lett.B684:6,2010Phys.Lett.B684:6,2010 Backward-angle η photoproduction from protons at E γ = GeV, M. Sumihama, et al., Phys. Rev. C 80, (R) (2009)Phys. Rev. C 80, (R) (2009) Near-threshold photoproduction of Λ(1520) from protons and deuterons, N. Muramatsu, J.Y. Chen, W.C. Chang, et al., Phys.Rev.Lett.103:012001,2009Phys.Rev.Lett.103:012001,2009 Evidence of the Θ + in the γd → K + K - pn reaction, T. Nakano, N. Muramatsu, et al., Phys.Rev.C79:025210,2009Phys.Rev.C79:025210,2009 Cross Sections and Beam Asymmetries for K + Σ *- photoproduction from the deuteron at E γ = 1.5-GeV GeV, K. Hicks, D. Keller, H. Kohri, et al., Phys.Rev.Lett.102:012501,2009Phys.Rev.Lett.102:012501,2009 Photoproduction of Λ(1405) and Σ 0 (1385) on the proton at E γ = GeV, M. Niiyama, H. Fujimura, et al., Phys.Rev.C78:035202,2008Phys.Rev.C78:035202,2008 ……

29 LEPS collaboration D.S. Ahn, J.K. Ahn, H. Akimune, Y. Asano, W.C. Chang, S. Date, H. Ejiri, H. Fujimura, M. Fujiwara, K. Hicks, K. Horie, T. Hotta, K. Imai, T. Ishikawa, T. Iwata, Y.Kato, H. Kawai, Z.Y. Kim, K. Kino, H. Kohri, N. Kumagai, Y.Maeda, S. Makino, T. Matsumura, N. Matsuoka, T. Mibe, M. Miyabe, Y. Miyachi, M. Morita, N. Muramatsu, T. Nakano, Y. Nakatsugawa, M. Niiyama, M. Nomachi, Y. Ohashi, T. Ooba, H. Ookuma, D. S. Oshuev, C. Rangacharyulu, A. Sakaguchi, T. Sasaki, T. Sawada, P. M. Shagin, Y. Shiino, H. Shimizu, S. Shimizu, Y. Sugaya, M. Sumihama H. Toyokawa, A. Wakai, C.W. Wang, S.C. Wang, K. Yonehara, T. Yorita, M. Yosoi and R.G.T. Zegers a Research Center for Nuclear Physics (RCNP), Ibaraki, Osaka , Japan b Department of Physics, Pusan National University, Pusan , Korea c Department of Physics, Konan University, Kobe, Hyogo , Japan d Japan Atomic Energy Research Institute, Mikazuki, Hyogo , Japan e Institute of Physics, Academia Sinica, Taipei 11529, Taiwan f Japan Synchrotron Radiation Research Institute, Mikazuki, Hyogo , Japan h School of physics, Seoul National University, Seoul, Korea i Department of Physics, Ohio University, Athens, Ohio 45701, USA j Department of Physics, Kyoto University, Kyoto, Kyoto , Japan k Laboratory of Nuclear Science, Tohoku University, Sendai , Japan l Department of Physics, Yamagata University, Yamagata, Yamagata , Japan m Department of Physics, Chiba University, Chiba, Chiba , Japan n Wakayama Medical College, Wakayama, Wakayama , Japan o Department of Physics, Nagoya University, Nagoya, Aichi , Japan p Department of Physics, Osaka University, Toyonaka, Osaka , Japan q Department of Physics, University of Saskatchewan, Saskatoon, S7N 5E2, Canada r Department of Applied Physics, Miyazaki University, Miyazaki , Japan 29

30 Photon beam asymmetry with Linearly Polarized Photons Production Plane //  Photon asymmetry =  1 Photon Polarization p p  Production Plane   Photon asymmetry = +1   

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 Diagram of meson photoproduction in tree level Forward Backward Meson exchange Resonances Nucleon exchange 31  p M p p, N*,  * u-channel t-channel  M p p M g NNM g NN*M …. Present data

32 Mass-reverse problem of three quark model uud(L=1) ½ - : uud(n=1) ½ + : uds(L=1) ½ - : harmonic oscillator : E = ( 2n + L + 3/2 ) h  d u u N*(1535) s s +qq pair solve this problem uud[ss] : S 11 (1535) uud[dd] : P 11 (1440) uds[uu] :  *(1405) B. S. Zou, NPA790, 110c should be the lowest S 11 (1535) P 11 (1440)  *(1405)  strong coupling to  N

33 Evidence of resonances in other reactions BES : N* from J/ , J/        production

34 Evidence of resonances BES : J/        PRL 97, (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) N*   N N*   N

35  + p   + + n ….N*?  + p   o + p ….  *? cos  cm   (1232) N(2190) 7/2 -  (2420) 11/2+ N(1720) 3/2+  (1920) 3/2+ PRD vol.6, 1 (1972)

36 d  /du vs. √ s 36 W=√s (GeV) Slopes are determined with the data at W<2.1 GeV. large slope 00

37 Differential cross sections d  /d  vs. W LEPS data SAID -partial-wave analysis Wide structure is seen above W=2.0 GeV 

Previous Work of LEPS M. Niiyama et al, Phys.Rev.C78:035202,2008 Differential cross sections for γp  K + Λ(1405) and K + Σ 0 (1385). E γ = 1.5 – 2.4 GeV target : H 2 (CH 2 – C) different line shapes of Λ(1405) for Σ + π - and Σ - π + decay mode.  isospin interference This work Higher E γ  new information about E γ dependence of the cross section of Λ(1405) Liquid hydrogen target was used.  no subtraction, more precise results total luminosity : 3 times larger than previous work This work Higher E γ  new information about E γ dependence of the cross section of Λ(1405) Liquid hydrogen target was used.  no subtraction, more precise results total luminosity : 3 times larger than previous work remarkable decrease of the production ratio of Λ(1405) to Σ 0 (1385) at higher E γ region.  different production mechanism and internal structure? Λ(1405) / Σ 0 (1385) = 0.54  0.17 at GeV =  at GeV

K + Missing mass spectrum  p  K + Y

Backward K +/0 angles Because of AC veto against  n  K 0  (1520); K 0 S  +  -,  (1520)  K - p was detected to compare  p and  n cross sections.  (1520) was identified by M(K - p) in LH 2 and LD 2 data. Background contributions were estimated by two complementary methods using MC (dashed line) and sideband (hatched area). LH 2 (0.61 pb -1 )LD 2 (1.15 pb -1 )  K-K-  (1520) K +/0 p p/n

41 u-channel process is dominant at very backward angles. Regge theory ; d  /du~s 2  (u)-2 at high energy.  (0) =  1/2 for N and N* exchange Higher energy region  =Re(  (u)) u=Mass2(GeV2) 9/2 7/2 5/2 3/2 1/2 -1/2 N(938) N(1680) N(2220)  (1232)  (1950) Baryon Regge trajectory

● Pad size : 5.1mm x 14.5mm gap : 0.5mm total 9layers 225pads/ 1sector (1350pads /6sector) ● Wire anode wire:27wires on 1sector Each wire strides 3sectors  total 54wires ・gate wires and shield wires are located above the anode/potential wires ・anode wire & potential wire wire spacing= 2.5mm (anode spacing 5mm) distance from pad plane = 4mm gate wire shield anode/potential Time Projection Chamber

● drift region : drift electrode～shield wire= 752mm ● drift velocity calculation with GARFIELD--- maximum at 160V/cm (～ 52mm/μs)  drift voltage = 12.1kV ● electric field definition with field cage (strip electrodes) ● Nitrogen gas is used to electrically isolate the field cage from the outer of the TPC. ● P10 gas Ar90% CH 4 10% Pad plane shield wire drift electrode P10 gas N 2 gas field cage strip electrode Time Projection Chamber outside inside

Analysis Particle Identification, Missing Mass spectrum of p (γ, K + ) X PID with Spectrometer PID with TPC p π+π+ π-π- K-K- p π+π+ π-π- K-K- K+K+ momentum vs. mass x charge Mass is calculated using track information. (momentum, TOF, track length) energy deposit vs. momentum x charge (plot for events in which K + is identified by the spectro- meter) Λ(1116) Σ 0 (1192) Λ(1520) Σ 0 (1385)/Λ(140 5) missing mass spectrum of p(γ,K + )X K + is identified by forward spectrometer. Σ 0 (1385) and Λ(1405) can not be separated due to their large width. Selection cuts using decay products detected by the TPC The yields of Hyperons are extracted from the missing mass spectrum of γ p  K + X.