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The reaction studied with an electromagnetic calorimeter FOREST

The reaction studied with an electromagnetic calorimeter FOREST. Yusuke TSUCHIKAWA R. Hashimoto, Q. He, T. Ishikawa, S. Masumoto, M. Miyabe , N. Muramatsu , H. Shimizu, Y. Tajima, H. Yamazaki, R. Yamazaki , a nd FOREST collaboration

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The reaction studied with an electromagnetic calorimeter FOREST

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  1. Thereaction studied with an electromagnetic calorimeter FOREST Yusuke TSUCHIKAWA R. Hashimoto, Q. He, T. Ishikawa, S. Masumoto, M. Miyabe, N. Muramatsu, H. Shimizu, Y. Tajima, H. Yamazaki, R. Yamazaki, and FOREST collaboration Research Center for the Electron Photon Science, Tohoku University Y. Tsuchikawa

  2. Thereaction studied with an electromagnetic calorimeter FOREST Outline • Motivation • FOREST experiment • 4 electromagnetic calorimeter FOREST • Analysis • Outline • Event selection • Kinematical fit • Results • Summary and Future plan Y. Tsuchikawa

  3. Motivation • Baryon resonances have been experimentally studied by means of meson production reactions for understanding Quantum Chromo Dynamics. • πN and ηNphotoproduction reactions have been intensively investigated until now -> KY channel… • photoproduction reactions are well-studied until now • HOWEVER, few data on Y. Tsuchikawa 3

  4. Motivation • photoproduction • Only NEUTRAL particles are implicated in this reaction →no charged particle (e.g. ) exchange term → few Born term contribution? -> study of Baryon Resonance Born terms Y. Tsuchikawa

  5. NKS data - photoproduction K. Tsukada et al., PhysRevC.78.014001, PhysRevC.83.039904 Y. Tsuchikawa

  6. Experiment Research Center for Electron Photon Science (ELPH) Layout of ELPH (～2012) STretcher-Booster Ring: 1.2 GeV electron synchrotron GeV- Beam line: 0.5-1.2 GeV photon • Photon beam line [ 11μΦ carbon fiber Picture?] • Brems. Photon Linac Y. Tsuchikawa

  7. Experiment 252 Lead/SciFimod.s PS×12 192 Pure CsI PS24 × 3 layers 62 Lead/Glass PS×18 4 electromagnetic calorimeter complex FOREST (Forward) (Backward) ～ 5 % Energy resolution (for 1 GeV) ～ 3 % ～ 7 % Liquid H2/D2 target MeV Y. Tsuchikawa

  8. Analysis– Outline • The final state: Branching ratio(BR)s: : 30.69%, : 63.9% (PDG value) • The proton in target deuterium is assumed as a spectator: not involve with the reaction The neutron in target deuterium is assumed as a rest particle • identification • Hit informations of calorimeter (and front hodoscope) • Energy and timing informations Assumed as a spectator Y. Tsuchikawa

  9. Analysis– particle identification • 4 neutral hits (expected ): • At least 4 neutral clusters are measured at same time • Selection of the combinations decayed from the same →test . Timing difference of 2 pions Y. Tsuchikawa

  10. Analysis– particle identification → reject 4γ average timing • Charged hits (expected ): • Charged cluster(s) @ Forward Calorimeter & Hodoscope • ID -> method Y. Tsuchikawa

  11. Analysis – Kinematical fitting 13 variables: Photon beam energy Kinematical fitting with 3 constraints invariant mass 」✕２ 1. 2. 「 missing mass」 3. Y. Tsuchikawa

  12. Analysis yield estimation invariant mass distribution Fitting function: 4th polynomial + gaussian • yield: ～ 8,500 events S/N ～ 10% Y. Tsuchikawa

  13. Analysis – Kinematics Ranges of CsI the maximum emission angle of proton < 40° → hit pattern of hodoscopes: Forward(): 2 & Central: 0 Momentum (GeV) Emission angle @ Lab. frame (deg) Y. Tsuchikawa

  14. Analysis – Kinematics • Azimuthal angle difference between system and system Accidental coincident events are subtracted by sideband (deg) Y. Tsuchikawa

  15. Analysis – Kinematics the maximum emission angle of proton < 40° → hit pattern of hodoscopes: Forward(): 2 & Central: 0 Energy dependence of K0 emission angle (Monte Calro simulation) Momentum (GeV) Emission angle @ Lab. frame (deg) Y. Tsuchikawa

  16. Analysis – Yield invariant mass Y. Tsuchikawa

  17. Analysis – Yield Real Data Incident photon energy binned 30 MeV reaction threshold ～1050MeV GEANT4 Simulation Y. Tsuchikawa

  18. Analysis – total cross section invariant mass A preliminary result of the total cross section Very Preliminary Y. Tsuchikawa

  19. Analysis – Background study 4 background candidates ✕ B.R. → mixed Y. Tsuchikawa

  20. Analysis – Background study a.u. Invariant Mass Y. Tsuchikawa

  21. Summary and Future plan • The photoproduction reaction is studied with an EM calorimeter FOREST at ELPH • About 8,500 events are confirmed in the reaction analysis • The reaction total cross section is estimated order of 1μb atGeV region • Future plan • Event selection • Differential cross section • Background event study Y. Tsuchikawa

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