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Hadron physics with GeV photons at SPring-8/LEPS II M. Niiyama (Kyoto Univ.) 1.Introduction to SPring-8/LEPS I 2.Physics motivation for LEPS II 3.Status.

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Presentation on theme: "Hadron physics with GeV photons at SPring-8/LEPS II M. Niiyama (Kyoto Univ.) 1.Introduction to SPring-8/LEPS I 2.Physics motivation for LEPS II 3.Status."— Presentation transcript:

1 Hadron physics with GeV photons at SPring-8/LEPS II M. Niiyama (Kyoto Univ.) 1.Introduction to SPring-8/LEPS I 2.Physics motivation for LEPS II 3.Status of LEPS II project 4.Summary Contents 1

2 Super Photon Ring 8 GeV (SPring-8) 2

3 b) Laser hutch a) SPring-8 SR c) Experimental hutch Compton  -ray Laser light 8 GeV electron Recoil electron Tagging counter Collision Backward-Compton scattering 36m 70m Schematic View of LEPS I Facility 3

4 Backward-Compton Scattered Photon  8 GeV electrons in SPring-8  + 351nm Ar laser (3.5eV ) 8W  ~ 2.4 GeV photon  + 266nm Solid+BBO (4.6eV ) 1W  +3.0 GeV photon  Laser Power ~6 W (351nm)  Photon Flux ~1 Mcps (2.4 GeV)  E  measured by tagging a recoil electron  E  >1.5 GeV,  E  ~10 MeV  Laser linear polarization % ⇒ Highly polarized  beam PWO measurement tagged Linear Polarization of  beam photon energy [GeV]photon energy [MeV] 4

5 1.5 Setup of LEPS I 5 Acceptance is limited in forward region

6 PRC 79, (2009)   LEPS vs CLAS LEPS forward angle CLAS large angle Physics motivation for LEPS II PRL 96, (2006) 6

7 Proton rejection by using dE/dx in Start Counter Pid = (Measured energy loss in SC) – (Expectation of KK) – (Half of expectation of proton) KKp only KKn and part of KKp Proton not tagged (Proton rejected) Proton tagged (  ~60%) K+K+ K-K- p n K+K+ K-K- p K+K+ K-K- or Signal enhancement is seen in proton rejected events. should be associated with  n reaction. p/n ratio: 1.6 before proton rejection 0.6 after proton rejection SC Peak structure is seen in the M(nK+) for proton rejected events. (Further more data will be taken at LEPS w/ larger acceptance for proton) 7

8 TOF Dipole Magnet 0.7 Tesla Target Start Counter DC2DC3 DC1SVTX AC(n=1.03) Photons Strong angular dependence of production rate? PRC 79, (2009)   LEPS vs CLAS LEPS forward angle CLAS large angle Physics motivation for LEPS II PRL 96, (2006) Angular dependence of production cross section may solve controversial situation. → 4  detector LEPS II. 8

9  J P =1/2- Mass spectrum of P-wave baryons 3/2 - 1/2 - N (1520) N (1535)   3/2 - 1/2 - Λ(1520) Λ(1405) 30 MeV K+N (1430) Physics motivation for LEPS II 9 uud (or udd) uds mass (MeV) Meson Baryon molecule picture has been proposed. (ex. Dalitz Phys. Rev ) 1) 3 quark or meson-baryon molecule? 2) If it is a K bar N molecule, what is the binding energy?

10 Higher mass of K bar N component of  (1405) D. Jido, et al. NPA725(2003) M.Niiyama. PRC78 Confirm by photoproduction. 10 V.K. Magas, E. Oset and A. Ramos, PRL 95

11 Hyperon production with K*(892)  Parity filter with linearly polarized photon E  K* K  natural parity ex. P=(-1) J K*(890),κ 11

12 Hyperon production with K*(892)  Parity filter with linearly polarized photon E  K* K  unatural parity ex. P= -(-1) J kaons 12

13 E  K* K  p   K- K*(890) Λ(1405) photoproduction with linearly polarized photon 13 T.Hyodo et. al, PLB593 High luminosity photon beam with E  >2.4 GeV. Detect K* + → K 0 s   →   →     →   →   Large acceptance charged / photon detector

14 Physics motivation for LEPS II   ’ meson in nuclear medium  Detection of scattered and decay particles simaltaneously M.Kaskulov, H. Nagahiro, S. Hirenzaki, and E. Oset PRC75, Magic momentum ~2.7 GeV, 0 degree 14

15 Recoil electron (Tagging) LEP (GeV  -ray) Laser room Inside SR bldg 30m long line 8 GeV electron Laser Outside SR bldg Experimental bldg Beam dump Backward Compton Scattering SR ring Schematic view of the LEPS2 facility 10 times high intensity : Multi laser injection &Laser beam shaping Large 4  spectrometer Best emittance e beam  pencil photon beam 15 BGO Gamma counter Two different exp. setup

16 pris m UV lasers (355/266 nm) expander AR-coated mirror w/ stepping motor LEP intensity  10 7 cps for E  <2.4 GeV beam (355 nm)  10 6 cps for E  <2.9 GeV beam (266 nm)  4-laser injection [x4]  Higher power CW lasers. 355 nm (for 2.4 GeV) 8 W  16 W, 266 nm (for 2.9 GeV) 1 W  2 W [x2]  Laser beam shaping with cylindrical expander [x2] 10 um 400 um laser Electron beam is horizontally wide.  BCS efficiency will be increased by elliptical laser beam. Need large aperture of the laser injection line  construct new BL chambers High Beam Intensity 16

17 Laser injection system 17 4 lasers in the laser hatch

18 SP8 18 New experimental hatch

19  first beam ( GeV~4Mcps w/ a single 24W laser) Energy spectra of photon beam w/ Laser w/o Laser mm Beam size in the experimental hatch 19

20  1320 BGO crystals  polar angle 24° ~ 146°  1GeV  RPC-TOF wall  Δt ~ 50 ps  flight length 12m  polar angle 0° ~ 5°  LH 2, LD 2 nuclear target  Backward meson production from this November.  charged particle tracker target   BGO EGG+TOF proton BGO EGG RPC-TOF 20

21 21 Detector performance π 0 reconstructed with BGO-EGG. Further calibration is underway. Time resolution of RPC-TOF RPC prototype BGO EGG RPC prototype 1m

22 Solenoid spectrometer 2.22 m  TPC DC  counter RPC TOP Magnet (BNL-E949) B=1 T  p/p 〜 1-5% for  deg detectors for photon, charged particle 3σ K/  /p separation < 2.7 GeV using RPC, TOP, AC Detector construction is underway Physics run from

23 Summary Backward Compton  beam line for hadron physics. Hadrons with s-quark. Recoilless production of light mesons in nucleus. Highly polarized photon beam up to 3 GeV. x10 luminosity. ~10Mcps. Two different experimental setups. BGO EGG + TOF Backward meson production from proton and nuclei Solenoid spectrometer Θ +, Λ(1405) First beam in Jan BGO EGG experiment from this November! 23


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