1. Photoproduction of η meson from proton at LEPS2 2014/2/20 Toshikazu Hashimoto @Kyoto Univ. 1

2. Physics Motivation Particle Data Group 2012 2

3. 3 A. Sarantev, CPC2009, 33(12)

4. p M. Sumihama et al., PRC80,052201 4

5. bump structure exist above 2GeV ? M. Sumihama et al., PRC80,052201 5 result of LEPS experiment

6. M. Williams et al., PRC80,045213 V. Crede et al., PRC80,055202 6 comparison to other experiment

7. Beam Asymmetry 7 D. Elsner et al., EPJA 33,147 ELSA LEPS2 coherent breamstrahlung D. Elsner et al., EPJ A 33,147

8. Beam Polarization 8 D. Elsner et al., EPJA 33,147 ELSA LEPS2 coherent breamstrahlung backward compton

9. LEPS2 Beamline 9 e-e-

10. Experimental setup 10 Drift Chamber BGO EGG p TOF wall RPC z x y target z = 1.5mz = 4.0m z = 12.5m

11. 11 z = 1.5mz = 4.0m z = 12.5m BGOEGG 11 Drift Chamber BGO EGG p TOF counterRPC 1320 BGO crystals egg-like shape 60 crystals/layer z x y 13 forward layers9 backward layers 144°

12. 12 z = 1.5mz = 4.0m z = 12.5m Target,CDC,Scinti 12 Drift Chamber BGO EGG p TOF wallRPC target is LiquidH 2. surrounding CDC. detecting charged particles Target Scintilation counter Cylindrical Drift Chamber z x y

13. z x y Forward Drift Chamber 13 Drift Chamber BGO EGG p TOF wall RPC FDC BGO 13 z = 1.5mz = 4.0m z = 12.5m

14. 14 z = 1.5mz = 4.0m z = 12.5m TOF wall 14 Drift Chamber BGO EGG p TOF wall RPC

15. 15 Drift Chamber BGO EGG TOF wall RPC 15 z = 1.5mz = 4.0m z = 12.5m 2 m 3.2 m

16. 16 BGOEGG area

17. 17 FDC and TOF area FDC and TOF area CDC and Scinti area CDC and Scinti area proton go through BGO proton go through BGO

18. 18 measured in LEPS experiment Acceptance branting ratio is 39%branting ratio is 33% average of Acc. is 0.26 0.39 * 0.26 = 0.10 average of Acc. is 0.18 0.33* 0.18 = 0.06

19. Yield estimation 19

20. 20 Background Signal detect with FDC and TOF detect with BGOEGG J.Barth et al, EPJA 18, 117 I.Horn et al, PRL 101, 202002 V. Crede et al., PRC80,055202 M. Sumihama et al., PRC80,052201

21. 21 All arbitrary

22. p mass cut 22 arbitrary All background decrease to 4.1%

23. 23 All arbitrary background decrease to 1.1% back to back

24. Summary 24