1 / 24

Photoproduction of η meson from proton at LEPS2

Photoproduction of η meson from proton at LEPS2. 2014/2/20 Toshikazu Hashimoto @Kyoto Univ. Physics Motivation. The family are predicted in quark model, but large number of them haven't been identified experimentally so far. Particle Data Group 2012. feature of N channel.

galvin
Download Presentation

Photoproduction of η meson from proton at LEPS2

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

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

  2. PhysicsMotivation The family are predicted in quark model, but large number of them haven't been identified experimentally so far. Particle Data Group 2012

  3. feature of N channel • production probes only contribution (not ). • has components. 　→we expect strong coupling to which have large components. S11(1535) P13(1720) D15(2070) A. Sarantev , CPC2009, 33(12)

  4. photoproduction from proton at LEPS • Backward-angle photoproduction • 1.6 • was measured inthe missing-massspectrum for p M. Sumihama et al., PRC80,052201

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

  6. comparison to other experiment descrepancy between LEPS and CLAS exists. → reconfirm at LEPS2 ? or reaction mechanism? V. Crede et al., PRC80,055202 M. Williams et al., PRC80,045213

  7. Beam Asymmetry : incident photon polarization : Beam Asymmetry : azimutial orientation of reaction plane to beam polarization p • differential cross section oscillate. • This amplitude is . • Spin-dependent amplitude can be measured. • High is necessary for precise study of coherent breamstrahlung LEPS2 ELSA polarization =1250～ 1340MeV polarization D. Elsner et al., EPJA 33,147 photoproduction off proton D. Elsner et al., EPJ A 33,147

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

  9. LEPS2 Beamline e- 1.3～3.0GeV Beam Intensity ～10Mcps

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

  11. BGOEGG 9 backward layers 13 forward layers y x z 144° p • 1320 BGO crystals • egg-like shape • 60 crystals/layer BGO EGG TOF counter RPC Drift Chamber z = 12.5m z = 1.5m z = 4.0m 11

  12. Target,CDC,Scinti Target y • target is LiquidH2. x z Cylindrical Drift Chamber • covering in polar angle. p Scintilation counter • surrounding CDC. • detecting charged particles BGO EGG TOF wall RPC Drift Chamber z = 12.5m z = 1.5m z = 4.0m 12

  13. Forward Drift Chamber FDC BGO y x z p • effective area is 1280mm • covering in polar angle • 1.5m from target • angular resolution is BGO EGG RPC Drift Chamber TOF wall z = 12.5m z = 1.5m z = 4.0m 13

  14. TOF wall p • covering in polar angle • 4.0m from target • timing resolution is 60ps (KEK) • timing resolution is 175ps (RS) BGO EGG RPC TOF wall Drift Chamber z = 12.5m z = 1.5m z = 4.0m 14

  15. RPC 3.2 m 2 m • time resolution is 50 ps • 12.5 m from target • vertical length is 2m • horizontal length is 3.2m • covering in polar angle BGO EGG RPC Drift Chamber TOF wall z = 12.5m z = 1.5m z = 4.0m 15

  16. MC simulation of sis detected with BGO egg. Forward Proton is detected with FDC and TOF. Sideway Proton is detected with CDC and Scintilator. BGOEGG area BGOEGG area [GeV/c] [GeV/c] [deg] [deg]

  17. MC simulation of sis detected with BGO egg. Forward Proton is detected with FDC and TOF. Sideway Proton is detected with CDC and Scintilator. proton go through BGO proton go through BGO [GeV/c] [GeV/c] FDC and TOF area FDC and TOF area CDC and Scinti area CDC and Scinti area [deg] [deg]

  18. Acceptance of detection is showed as function of polar angle. + p + p Acceptance Acceptance measured in LEPS experiment measured in LEPS experiment branting ratio is 39% branting ratio is 33% average of Acc. is 0.18 average of Acc. is 0.26 0.33* 0.18 = 0.06 0.39 * 0.26 = 0.10

  19. Yield estimation Yield ofprocess • ~ 0.05 /str : ref) M. Sumihama et al., PRC80,052201 • 4.0 cm LH2 target ⇒ • Photon beam intensity ~1Mcps • ⇒ generate • counts/month • Assume 16% acceptance • ⇒ yield ~60k counts/month

  20. MC simulation of Signal detect with FDC and TOF (0.05 /str) detect with BGOEGG (br =39%) (br =33%) Background 3 I.Horn et al, PRL 101, 202002 0.7 V. Crede et al., PRC80,055202 ~10 M. Sumihama et al., PRC80,052201 5.5 J.Barth et al, EPJA 18, 117

  21. MC simulation of s invariant mass select mass region of All mass cut (2 and 6) arbitrary combinational combinational combinational cut region is main background is and invariant mass [GeV/c2]

  22. MC simulation of missing mass All p mass cut (2 and 6) arbitrary combinational combinational combinational cut region is background decrease to 4.1% missing mass [GeV/c2]

  23. MC simulation of All angle between and proton (2 and 6) If reaction is two-body decay, the equation holds. combinational back to back combinational combinational cut cut arbitrary arbitrary background decrease to 1.1% [deg] [deg]

  24. Summary • production has the advantage of resonance study. • A bump structure has been observed above 2.0GeV in total energy in LEPS experiment, but this is not consistent with CLAS experiment. • We are planning to measure diffrential cross section of photoproduction and beam asymmetry at LEPS2. • We want to decide origin of bump structure,N* or production mechanism. • 60k events/month in BGO experiment at LEPS2. • Background decrease to 1% by detecting proton with FDC and TOF counter. • We will estimate backgroundwhen proton is detected with CDC and Scinti. • Data taking will be started in April.

More Related