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International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) Neutral kaon photoproduction at LNS, Tohoku Masashi Kaneta for the NKS/NKS2 collaboration Department of Physics Tohoku University

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International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) Introduction 2 Masashi Kaneta, Tohoku Univ.

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International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) Physics Motivation Investigation of strangeness production mechanism Threshold region of the production No resonance decay effect Good for comparison with models Give theoreticians base data to address Coupling constant Resonance contribution Small cross-section, i.e. high statistics data is required Neutral channel in the strangeness photo-production Past experiments studied by K + production until 2002 Not enough data of differential cross-section of +n K 0 + 3 Masashi Kaneta, Tohoku Univ.

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International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) Model dependence in cross-section Models are based on K + experimental data There is large model dependence for K 0 cross-section Solid-White: Kaon-MAID Dash-Red: Saclay-Lyon A (rkk=-0.45) 4 Masashi Kaneta, Tohoku Univ.

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International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) Masashi Kaneta, Tohoku Univ. 5 The Experiments at LNS, Tohoku

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International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) The Experiments The series of experiments by neutral kaon spectrometer at LNS, Tohoku Univ. The 1 st generation (NKS) Used TAGX spectrometer of INS and successfully done in 2004 The first measurement of the cross-section of neutral channel near the threshold Carbon target results: PLB651(2007)269 Liquid D 2 target results: PRC78(2008)014001 It is found that some improvements are necessary: the forward region, and the vertical position information in the chambers The 2 nd generation (NKS2) Constructed in 2004-2006 from scratch Commissioning run in 2006 The data taking with liquid D 2 target in 2006-2007 An upgrade is on going 6 Masashi Kaneta, Tohoku Univ.

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International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) The NKS (1998-) and NKS2 (2004-) collaboration Akita University, Akita, Japan A. Sasaki Ichinoseki National college of Technology, Ichinoseki, Japan O. Konno Department of Physics, Tohoku University, Sendai, Japan N. Chiga, B. Beckford, M. Ejima, T. Fujii, Y. Fujii, T.Fujibayashi, T. Gogami, K. Futatsukawa, O. Hashimoto, K. Hosomi, K. Hirose (a), A. Iguchi, S. Kameoka, H. Kanda, M. Kaneta, H. Kato, D. Kawama, T. Kawasaki, C. Kimura, S. Kiyokawa, T. Koike, T. Kon, Y. Ma, K. Maeda, N. Maruyama, A. Matsumura, Y. Miyagi, Y. Miura, K. Miwa, S.N. Nakamura, H. Nomura, A. Okuyama, A. Ohtani, T. Otani, M. Sato, A. Shichijo, K. Shirotori, T. Takahashi (b), H. Tamura, N. Taniya, H. Tsubota, K. Tsukada (c) N. Terada, M. Ukai (d), D. Uchida, T. Watanabe, T. Yamamoto, T. Yamamoto, H. Yamauchi, K. Yokota Laboratory of Nuclear Science, Tohoku University, Sendai, Japan T. Ishikawa, T. Kinoshita, H. Miyahara, T. Nakabayashi, H. Shimizu, K. Suzuki, T. Tamae, T. Terasawa, H. Yamazaki Department of Nuclear Science, Lanzhou University, Lanzhou, China Y.C. Han, T.S. Wang Nuclear Institute, Czech Republic P. Bydzovsky, M. Sotona Masashi Kaneta, Tohoku Univ. 7 Student name is shown with underline (a) Now at LNS, Tohoku University, Japan (b) Now at KEK, Japan (c) Now at RIKEN, Japan (d) Now at Gifu University, Japan

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International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) Tagged Photon Beam Line at LNS 150 MeV electron beam from LINAC 1.2 GeV Stretcher-Booster Ring Photon tagging system Sweep magnet Neutral Kaon Spectrometer Neutral Kaon Spectrometer 2 8 Masashi Kaneta, Tohoku Univ.

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International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) Tagged Photon Beam at LNS Radiator Photon beam Electron beam on carbon wire (11 m ) Tagged by electron which has energy loss E =0.8-1.1 GeV from 1.2 GeV electron beam 6 MeV coverage per tagging counter Time resolution: ~240 ps Tagger Backup Tagger Finger Scattered e - e - on orbit 9 Masashi Kaneta, Tohoku Univ.

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International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18)NKS There are two arms in one dipole magnet IH:Inner Hodoscope SDC:Straw Drift Chamber CDD:Cylindrical Drift Chamber OH:Outer Hodoscope EV:Electron Veto No acceptance in forward region 10 Masashi Kaneta, Tohoku Univ.

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International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18)NKS2 Masashi Kaneta, Tohoku Univ. 11 Dipole Magnet B=0.42 [T] at the center Inner Hodoscope Trigger Start timing of TOF Outer Hodoscope Trigger Stop timing of TOF Straw Drift Chamber Tracking (2D) Cylindrical Drift Chamber Tracking (3D) Electron Veto Counter beam 1.0 m A vertical cross section along beam

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International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) NKS2 Photo Masashi Kaneta, Tohoku Univ. 12

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International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 0.0 0.5 1.0 1.0 0.5 1.0 0.5 0.0 0.5 1.0 1.0 0.5 1.0 0.5 Masashi Kaneta, Tohoku Univ. 13 Red contour: D 2 target K 0 S production cross-section (Kaon-MAID model) Gray contour: Acceptance of K 0 S ( ) in NKS and NKS2 K 0 S momentum [GeV/c] Red contours: K 0 S cross-section Kaon-MAID model calculation on a D 2 target Energy threshold 0.915 GeV in +n K 0 + E =0.8-1.1 GeV at LNS 0.0 0.5 1.0 1.0 0.5 1.0 0.5 cos lab E = 0.9-1.0 GeV E =1.0-1.1 GeV NKS NKS2 543210543210 efficiency [%] Comparison of Acceptances

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International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) NKS Masashi Kaneta, Tohoku Univ. 14 Results from the 1 st generation experiment NKS

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International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) Particle Identification Good pion/proton separation TOF: ~510ps Masashi Kaneta, Tohoku Univ. 15

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International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) Decay Volume Cut Main background of K 0 S e + e from photon conversion can be rejected by opening angle cut and Electron Veto counter from and can be rejected by decay volume cut With the decay volume cut, the S/N increased 16 Masashi Kaneta, Tohoku Univ.

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International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) Invariant Mass of + - B.G.1 B.G.2 B.G.0 B.G.0: e + e (miss-ID as pions) B.G.1: from K 0 S and from B.G.2: from and After applying decay volume cut and opening angle cut (-0.9