1. 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

2. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) イントロダクション Introduction 2 Masashi Kaneta, Tohoku Univ.

3. 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.

4. 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.

5. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 東北大学原子核理学研究施設での実験 Masashi Kaneta, Tohoku Univ. 5 The Experiments at LNS, Tohoku

6. 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.

7. 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

8. 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.

9. 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.

10. 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.

11. 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

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

13. 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 cosθ lab E  = 0.9-1.0 GeV E   =1.0-1.1 GeV NKS NKS2 543210543210 efficiency [%] Comparison of Acceptances

14. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 第一世代実験 NKS の結果 Masashi Kaneta, Tohoku Univ. 14 Results from the 1 st generation experiment NKS

15. 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

16. 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.

17. 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<cos   <0.8), invariant mass of     pair is obtained K 0SK 0S 17 Masashi Kaneta, Tohoku Univ. K 0SK 0S

18. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) Results of NKS: K 0 S cross section The first data of K 0 S cross section from  +n reaction near the threshold –vertical bar: statistical error –histogram: systematic error 18 Masashi Kaneta, Tohoku Univ.

19. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) Isobar models (Effective Lagrangian Approach) Kaon-MAID [T. Mart, C. Bennhold, PRC61 (2000) 012201(R)] –Resonances in coupling: N(1650) S 11, N(1710) P 11, N(1720) P 13, N(1895) D 13, K * (892), K 1 (1270) –Reaction of input data: K + , K +  0, K 0  + –including hadronic form factor and contact term Saclay-Lyon A [T. Mizutani et al., PRC58 (1998) 75] –Resonances in coupling: N(1720) P 13, K * (892), K 1 (1270),  (1405) S 01,  (1670) S 01,  (1810) P 01,  (1660) P 11 –Reaction of input data: K +  –No hadronic form factor 19 Masashi Kaneta, Tohoku Univ.

20. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) Comparison of p( , K + )  with n( , K 0 )  20 p( , K + )  reaction n( , K 0 )  reaction 1.Hadronic coupling Isospin symmetry 2.Electromagnetic coupling ① Helicity amplitude : photo-coupling of charged and neutral nucleon resonances. ② Decay width : photo-coupling of charged and neutral kaon resonances. However, the decay width of K 1 resonance is not known.  0.45 in Kaon-MAID from K 0  + reaction Free parameter in SLA r(K 1 K  ) represented as rkk from the next slide r(K * K  ) = r(K 1 K  ) : Masashi Kaneta, Tohoku Univ. g(K *0 K 0  ) g(K *+ K +  ) = -1.53

21. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) Comparison of K 0 S Cross-section with Models Comparison of K 0 S Cross-section with Models Fermi motion effect of neutron is included in the calculation –Non-relativistic Bonn OBEPQ (one-boson-exchange-potential in q-space) deuteron wave function [R. Machleidt et al., Phys. Rept. 149 (1987) 1-89 ] Data prefer Saclay-Lyon A model and phenomenological parametrization PH1 –Note: PH2 is the inverse angular distribution to that of PH1 21 Masashi Kaneta, Tohoku Univ.

22. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) What is the model suggesting? Masashi Kaneta, Tohoku Univ. 22 Data prefer Saclay-Lyon A model and parametrization PH1 In the CM frame, the angle dependence of K 0 S cross sections are: Backward peak is suggested forwardbackward forwardbackward

23. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 第二世代実験 NKS2 の結果 Results from the 2 nd generation experiment NKS2 23 Masashi Kaneta, Tohoku Univ.

24. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) Particle Identification An example –Liq. D 2 target –two-tracks event –  TOF: ~350ps –opening angle cut is applied to reduce e + e - -0.9 < cos   < 0.8 Masashi Kaneta, Tohoku Univ. 24 TOF(IHL2-OHVL4) charge sign  p  

25. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) Decay Vertex Distribution Masashi Kaneta, Tohoku Univ. 25  Vacuum cell region Target Cell Opening angle cut -0.9<cos   <0.8 is required Target Cell Decay vertex point [cm] number of counts Decay vertex is reconstructed from trajectories of positive and negative charged particle pair This distribution is projected on beam axis direction

26. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) Recent Results (K 0 ) Masashi Kaneta, Tohoku Univ. 26 0.9<E  <1.0 [GeV] 1.0<E  <1.1 [GeV] K 0 momentum [GeV/c] d  /dp [  b c/GeV] K 0 S cross-section on Liq. D 2 target –analyzed ~30% of recorded data –  +n  K 0 S +  is dominant –expanding angle New region: cos  KLab <0.9 –Capability to discuss angular dependence Background is estimated by side-bands     invariant mass 0.0 -0.2 0.2 0.4 0.6 0.8 0.0 0.20.4 0.6 0.0 0.20.4 0.6 0.0 -0.2 0.2 0.4 0.6 0.8 0.0 -0.2 0.2 0.4 0.6 0.8 0.0 -0.2 0.2 0.4 0.6 0.8 0.0 -0.2 0.2 0.4 0.6 0.8 1.0 0.0 -0.2 0.2 0.4 0.6 0.8 1.0 cos  Lab 0.8 - 0.9 0.7 - 0.8 0.9 – 1.0

27. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) Recent Results (  ) Masashi Kaneta, Tohoku Univ. 27 Λ cross-section on Liq. D 2 target –Analyzed ~30% of recorded data –  +n  K 0 S +  and  +p  K + +  are dominant 0.0 0.2 0.4 0.6 0.8 1.0 1.2  momentum [GeV/c] cos   Lab 0.90 - 0.95 0.80 - 0.90 0.95 – 1.00 0.9<E  <1.0 [GeV]1.0<E  <1.1 [GeV] Background is estimated by side-bands p   invariant mass d  /dp [  b c/GeV]

28. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) Recent Results (cont’) K 0 measurement –Extends the study to discuss cos  dependence –Total number of the particle is similar to NKS statistics in each (E , p, cos  ) bin are smaller..  measurement –Large statistics (>10 times of NKS) –Data is from two reaction (  +p and  +n ) need to separate to compare a model of elementally process K +  coincidence measurement is important –Three/Four tracks event analyses Recent results will be shown by Kenta Futatsukawa in the poster session –Need to increase the acceptance Detector upgrade project is on going Masashi Kaneta, Tohoku Univ. 28

29. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) Expanding the Study Physics motivation –K+Y coincidence measurement Advantage –No Fermi motion correction Differentials cross section Lambda polarization Detector upgrade –Replacing inner detector Replace straw drift chamber by a 3D tracker –increase the acceptance Two-side-read-out hodoscope –increase TOF resolution to have better particle separation Masashi Kaneta, Tohoku Univ. 29

30. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) Acceptance with New Detectors Masashi Kaneta, Tohoku Univ. 30 The acceptance will increase – ~8 times (1):all K 0 S (  +  - ) +    - p) events (2):the four daughters pass through VDC with two OH Hits (3): four daughters pass through OH Note: No decay volume cut is applied  p  - channel) K 0 S (  +  - channel) Note: single tracking efficiency: assumed to be 90%

31. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) New Inner Detectors Masashi Kaneta, Tohoku Univ. 31 Vertex Drift Chmaber 8 Layers u,u’,v,v’,u,u’,v,v’ structure Photo taken in Nov. 2008

32. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) Event Display from the Last Run Chamber commissioning and trigger study runs are held Sep. and Nov. 2008 Masashi Kaneta, Tohoku Univ. 32  beam

33. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) Event Display from the Last Run Chamber commissioning and trigger study runs are held Sep. and Nov. 2008 Masashi Kaneta, Tohoku Univ. 33  beam

34. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18)Summary The investigation of neutral kaon photoproduction at LNS, Tohoku –Tagged photon beam (E  =0.8-1.1 GeV)at LNS, Tohoku The first measurement of neutral kaon via  +n reaction near the threshold by NKS –Carbon target: PLB651(2007)269 –Liquid D 2 target: PRC78(2008)014001 The new spectrometer NKS2 covers larger acceptance –Over all kinematic region –Capability to discuss angular dependence of cross-section The upgrade –New inner detectors –Expanding the solid angle –Coincidence measurement of K+L ~8 times acceptance –The performance is tested by commissioning run Masashi Kaneta, Tohoku Univ. 34

35. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) バックアップ Masashi Kaneta, Tohoku Univ. 35 Backup

36. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) Phenomenological Parameterization Masashi Kaneta, Tohoku Univ. 36

37. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) Masashi Kaneta, Tohoku Univ. Figure of Merit for K 0 S +  Event Acceptance as a function of   –No drastic change over  K  K in CM [degree] FoM four tracks pass through VDC four tracks pass through OH

38. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) Masashi Kaneta, Tohoku Univ.Gain Momentum [GeV/c] cos  K0SK0S  a.u. ratio K 0 S /  coincidence events to single K 0 S / 

39. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) Particle separation by TOF Masashi Kaneta, Tohoku Univ. 39