Recent Results from LEPS/SPring-8 Ken Hicks Ohio University, USA Sept. 21, 2009 on behalf of LEPS collaboration International Conference on Quark Nuclear Physics 2009, Beijing, China

Outline Short description of LEPS Photoproduction of KY Photoproduction of KY* Photoproduction of K*Y Search for the  + using K + K - from deuterium K. Hicks, Ohio U.QNP20092

Schematic view of the LEPS facility K. Hicks, Ohio U.QNP20093 b) Laser hutch a) SPring-8 SR ring c) Experimental hutch Compton  -ray Laser light 8 GeV electron Recoil electron Tagging counter 36m 70m

Backward-Compton Scattered Photon 8 GeV electrons in SPring nm Ar laser (3.5eV ） E  measured by tagging a recoil electron   E  ~10 MeV Laser Power ~6 W  Photon Flux ~1 Mcps Laser linear polarization % ⇒ Highly polarized  beam QNP20094 PWO measurement tagged Linear Polarization of  beam photon energy [GeV]photon energy [MeV]

K. Hicks, Ohio U.QNP20095 LEPS detector at SPring-8/LEPS 1.5

Particle ID at LEPS K. Hicks, Ohio U.QNP20096 TOF Dipole Magnet 0.7 Tesla Target Start CounterDC2DC3 DC1SVTX AC(n=1.03) Photons Momentum [GeV/c] K/  separation K+K+ ++ Mass/Charge [GeV/c 2 ]

Strangeness Production K. Hicks, Ohio U.QNP20097 Goals: data for  (1020) ,  hyperons Features: Forward angle measurement, including 0 o Polarization observables Strangeness production

 (1116) &  (1193) ReactionDetection Method & Measurements Major AuthorsReference K+ missing; beam asymmetry R.G.T. Zegers, M. Sumihama PRL 91, (2003) K+ missing; beam asymmetry, differential cross section M. SumihamaPRC 73, (2006) p  -; beam asymmetry, differential cross section K. Hicks, T. Mibe, M. Sumihama PRC 76, (R) (2007) K+ missing; beam asymmetry, differential cross section H. KohriPRL 97, (2006) K. Hicks, Ohio U.QNP20098

 (1385),  (1405),  (1520) ReactionDetection Method & Measurements Major AuthorsReference  ; differential cross section M. Niiyama, H. Fujimura PRC 78, (2008) K+ missing; beam asymmetry, differential cross section K. Hicks, D. Keller, H. Kohri PRL 102, (2009) pK, KK; beam asymmetry, decay asymmetry, differential cross section N. Muramatsu, J. Y. Chen, W.C. Chang PRL 103, (2009) K+ missing; beam asymmetry, differential cross section H. KohriaxXiv: K. Hicks, Ohio U.QNP20099

Born Diagrams QNP s-channel t-channelcontact term u-channel

Angular Distributions of  p  K +  K. Hicks, Ohio U.QNP s-channel t-channel u-channel R. Bradford et al. (CLAS Collaboration), PRC 73, (2006)

Angular Distributions of  p  K +  K. Hicks, Ohio U.QNP s-channel t-channel u-channel R. Bradford et al. (CLAS Collaboration), PRC 73, (2006)

Energy Distribution K. Hicks, Ohio U.QNP R. Bradford et al. (CLAS Collaboration), PRC 73, (2006) LEPS

Missing Mass of K+ K. Hicks, Ohio U.QNP LH 2 data p( , K + ) GeV/c 2  00  (1520)  (1405)  (1385) LD 2 data   (1520)  (1405)  0 (1385)  - (1385) 0, -0, - N( , K + ) GeV/c 2 spectrometer  K+ Y p/d

Invariant Mass and Its Missing Mass K. Hicks, Ohio U.QNP spectrometer  K- K+ p p ** K+K+

Energy Dependence of Cross Sections K. Hicks, Ohio U.QNP  K+K*-exchange by M. Guidal (Regge model).  Isobar + Regge by T. Mart and C. Bennhold.  Gent isobar model by T. Corthals LEPS SAPHIR CLAS  0 (1193)  (1116) M. Sumihama et al. (LEPS Collaboration), PRC 73, (2006)

Differential Cross Sections K. Hicks, Ohio U.QNP No forward peaking.  0 (1193)  (1116) Forward peaking. Need Regge poles. LEPS CLAS

Photon-Beam Asymmetry If the dominant contributions are from t- channel K and K* exchange, they can be further distinguished by photon-beam asymmetry using linearly polarized photon beam. A=(  perp -  para )/ (  perp +  para ) If A is negative (positive), the interaction is dominated by the electric (magnetic) component induced by K (K*) exchange. K. Hicks, Ohio U.QNP200918

Photon Beam Asymmetry K. Hicks, Ohio U.QNP  0 (1193)  (1116) Larger contribution from t-channel K* exchange.

Uncertainties in the Theoretical Models K. Hicks, Ohio U.QNP T. Mart and A. Sulaksono PRC74 (2006) SAPHIR/LEPS CLAS/LEPS SAPHIR/CLAS/LEPS Used data for fitting in models. Photon asymmetry

Backward K +  photoproduction K. Hicks, Ohio U.QNP Detect  (p  - ) at forward angles  (1116)  p   X K+K+  p  p     K +  , K* , KY* K. Hicks et al. (LEPS Collaboration), PRC 76, (R) (2007)

Theoretical Models K. Hicks, Ohio U.QNP T. Mart and A. Sulaksono PRC74 (2006) SAPHIR/LEPS CLAS/LEPS SAPHIR/CLAS/LEPS Used data to fit models. Photon asymmetry

 (1520) Experiments LAMP2 (real photon) CLAS (virtual photon) K. Hicks, Ohio U.QNP D. P. Barber et al. (LAMP2 Collaboration), Z. Phys. C 7, 17 (1980). S. P. Barrow et al. (CLAS Collaboration), PRC 64, (2001).

Toki, Garcia-Recio and Nieves, PRD, 77, (2008) The chiral unitary model predicts a small coupling between Λ(1520) and NK*. K. Hicks, Ohio U.QNP Main contribution comes from the K exchange process

Nam, Hosaka, and Kim, PRD71, (2005) K. Hicks, Ohio U.QNP Production from Proton Production from Neutron Large np isospin asymmetry.

Photoproduction of Λ* QNP N. Muramatsu et al. (LEPS Collaboration), PRL 103, (2009)

Cross sections on H and D The ratio between deuterons and protons was 1.02±0.11. Production from neutrons is strongly suppressed at LEPS kinematics. Large isospin asymmetry. K. Hicks, Ohio U.QNP200927

Importance of Contact Term K. Hicks, Ohio U.QNP A. Hosaka, Workshop of “Challenge to New Exotic Hadrons with Heavy Quarks”.

Isospin Asymmetry in  + Production K. Hicks, Ohio U.QNP200929

Cross Sections:  n  K +  * - K. Hicks, Ohio U.QNP Calculations are from Oh, Ko & Nakayama, averaged over the bin size shown. Cross sections are only measured at forward angles: complementary to the CLAS data. K. Hicks et al. (LEPS Collaboration), PRL 102, (2009)

Beam Polarization Dependence K. Hicks, Ohio U.QNP Due to statistics, only three bins in beam energy ( , , GeV) were used for the beam asymmetry fits. The K +  - final state (left), shows the opposite sign for the beam asymmetry when compared with the K +  * - final state (right).  n  K +  -  n  K +  * -

Beam Asymmetries K. Hicks, Ohio U.QNP Present results (solid points) compared with previously published data (open points) from Kohri et al. (PRL, 2006) Curve (Oh, Ko, Nakanyama) assumes 3-quark structure to the  *. A 5-quark component would have asymmetry of -1 (model of B. Zou).

K* 0 photoproduction at LEPS K. Hicks, Ohio U.QNP K*

K. Hicks (Ohio)Hyp-X Conf.34 Theory: a) K* + , b) K* 0  + SOLID BLUE: no kappa form factor; DASHED RED: with kappa form factor Y. Oh and H. Kim, hep-ph/

K* + and K* 0 Beam Asymmetry K. Hicks, Ohio U.QNP Large sensitivity to the kappa meson for linear polarization.

Experimental status of  + Searches K. Hicks, Ohio U.QNP Not seen in the most of the high energy experiments: The production rate of  + /  (1520) is less than 1%. No signal seen in CLAS  p, KEK-PS (K +,  + ) experiments. The width must be less than 1 MeV. (DIANA and KEK-B). LEPS could be inconsistent with CLAS  d experiment. Production rate depends on reaction mechanism. K* coupling should be VERY small. K coupling should be small. Strong angle or energy dependence.

LEPS Good forward angle coverage Poor wide angle coverage 1.5 – 2.4 GeV photons Symmetric acceptance for K + and K - M KK >1.04 GeV/c 2 Select quasi-free process CLAS Poor forward angle coverage Good wide angle coverage 1.0 – 3.5 GeV photons Asymmetric acceptance M KK > 1.07 GeV/c 2 Require re-scattering or large Fermi momentum of a spectator ~ Differences: LEPS and CLAS for  n  K -   K. Hicks, Ohio U.QNP LEPS:  LAB < 20 degree CLAS:  LAB > 20 degree K - coverage:

Minimum Momentum Spectator Approximation (MMSA) K. Hicks, Ohio U.QNP γ d K-K- K+K+ Nucleon from decay or scattering Spectator nucleon p n 4 momentum of pn system M pn and p tot |p CM | and v pn p CM - p CM v pn We know Direction of p CM is assumed so that the spectator can have the minimum momentum for given |p CM | and v CM. at rest tagged detected

Double-role of MMSA K. Hicks, Ohio U.QNP coherent inelastic quasi-free Clean-up Estimation of p F p min

Results of  (1520) analysis Simple ( ,K + ) missing mass: No correction on Fermi motion effect. pK - invariant mass with MMSA: Fermi motion effect corrected. K. Hicks, Ohio U.QNP  (-2lnL) =55.1 for  ndf=2  7.1 

Results of   analysis  (-2lnL) =31.1 for  ndf=2  5.2  Simple ( ,K - ) missing mass: No correction on Fermi motion effect. nK + invariant mass with MMSA: Fermi motion effect corrected. K. Hicks, Ohio U.QNP

Probability of 2 x is not good enough. “Extraordinary claim requires extraordinary evidence.” Higher statistics data was collected in with the same experimental setup. Blind analysis is under way to check the Θ + peak Next step K. Hicks, Ohio U.QNP200942

Summary LEPS data has had a significant effect on our understanding of strangeness production. Recent results on  * reveals the importance of the contact term in photoproduction. – Large isospin difference of production cross section. Recent results on  * shows that SU(3) flavor symmetry works well for the baryon decuplet. – Beam asymmetry is more negative than expected. Search for  + is still in progress. – There are many constraints from other data. K. Hicks, Ohio U.QNP200943

K. Hicks, Ohio U.QNP LEPS new beam line (LEPS2) Beam upgrade: Intensity --- High power laser, Multi laser(x4) --- Laser elliptic focus  2x10 6  10 7 /sec for 2.4 GeV 2x10 5  10 6 /sec for 3 GeV Energy --- Laser with short, re-injected Soft X-ray+BCS (2 nd stage),  up to ~7.5 GeV Detector upgrade: (reaction process & decay process) Scale & --- General-purpose large 4  detector Flexibility Coincidence measurement of charged particles and neutral particles (photons)  BNL/E949 detector DAQ --- High speed for the minimum bias trigger Physics: Multi-quark (>3) Workshop on LEPS2 (2005/7, 2007/1)

Missing mass of p ( , K+) X K. Hicks, Ohio U.QNP H. Kohri et al. (LEPS Collaboration), arXiv:  Possible bump structure at W~2.1 GeV?  Better description of energy dependence with the inclusion of a nucleon resonance w/o N* with N*

Beam Asymmetry of  (1520) K. Hicks, Ohio U.QNP Contribution from t-channel K* exchange is dominant at W>2.2 GeV.