1. The Investigation of Strangeness Photoproduction in the Threshold Region at LNS-Tohoku Masashi Kaneta for the NKS/NKS2 collaboration Department of Physics, Tohoku University

3. Introduction Motivation –Understanding the mechanism of strangeness production via photoproduction on nucleon focusing on neutral channel Characteristics –Neutral channel K + data is not enough to make a model to predict cross section of neutral channel K 0 data is the KEY of the study –Threshold region No resonance decay effect in the final products Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University 3

4. Introduction Motivation –Understanding the mechanism of strangeness production via photoproduction on nucleon focusing on neutral channel Characteristics –Neutral channel K + data is not enough to make a model to predict cross section of neutral channel K 0 data is the KEY of the study –Threshold region No resonance decay effect in the final products Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University 4

5. Introduction Motivation –Understanding the mechanism of strangeness production via photoproduction on nucleon focusing on neutral channel Characteristics –Neutral channel K + data is not enough to make a model to predict cross section of neutral channel K 0 data is the KEY of the study –Threshold region No resonance decay effect in the final products Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University 5

6. Channels of Strangeness Production Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University +p K+++p K++0+p K0+++n K0++n K0+0+n K++-+p K+++p K++0+p K0+++n K0++n K0+0+n K++- +N K+Y+N K+Y 6

7. The Cross-section Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University Proton target Mainly K + data Figure:PRC74(2006)044004 No data before NKS experiment had started Data: SAPHIR Lines: Kaon-MAID model 7

8. Different predictions by Models Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University 0.9 1.01.1 1.2 1.31.4 1.5 E  [GeV] 0.9 1.01.1 1.2 1.31.4 1.5 +p K+++p K+++p K+++p K++ +n K0++n K0++n K0++n K0+ cos 1.0 0.0  [b] 3 2 1 0 10 5 0 d  d  [b/sr] 0 0 1 1 Kaon-MAID Saclay-Lyon A E  =1.05[GeV] Both models show similar results Huge differences 8

9. Introduction Motivation –Understanding the mechanism of strangeness production via photoproduction on nucleon focusing on neutral channel Characteristics –Neutral channel K + data is not enough to make a model to predict cross section of neutral channel K 0 data is the KEY of the study –Threshold region No resonance decay effect in the final products Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University 9

10. Introduction Motivation –Understanding the mechanism of strangeness production via photoproduction on nucleon focusing on neutral channel Characteristics –Neutral channel K + data is not enough to make a model to predict cross section of neutral channel K 0 data is the KEY of the study –Threshold region No resonance decay effect in the final products Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University 10

12. Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University 12 Theoretical Study: Effective Lagrangian Approach Hadron coupling –Isospin symmetry Electromagnetic (photo) coupling –Helicity amplitude Charged and neutral nucleon resonances –Decay width Charged and neutral Kaon resonances However, the decay width of K 1 resonance is not known    N N N K K K s channel t channel u channel Y NN*NN* K,K *,K 1 Y Y YY*YY*  N K Contact term Y 0.45 in Kaon-MAID, estimated from pK 0  + data Free parameter in SLA

13. Models Kaon-MAID –T.Mart, C.Bennhold, PRC61 (2000) 012201(R) –Input: pK + , pK +  0, pK 0  + –Resonances: N(1650) S 11, N(1710) P 11, N(1720) P 13, (1900) S 31, (1910) P 31 K*(892), K 1 (1270) –Hadronic form factor, contact term Saclay-Lyon A –T. Mizutani et al. PRC58 (1998) 75 –Input: pK +  –Resonances: N(1720) P 13 (1405), (1670), (1810), (1660) K*(892), K 1 (1270) –No hadronic form factor Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University 13

15. Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University 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 15 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

16. Laboratory of Nuclear Science (LNS), Tohoku Univ. at Sendai Electron beam up-to 1.2 GeV Two tagged-photon beam lines –Bremsstrahlung –E  =0.8-1.1 GeV (from E e =1.2 GeV) –Tagged-photon beam rate > ~MHz 16 Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University

17. Tagged Photon System BM4 tagger BM5 tagger to the other experimental hall NKS2 Radiator (Carbon wire) to make Bremsstrahlung B Photon Beam Electron (1.2 GeV) Scattered electron (0.1-0.4 GeV) Tag F Tag B 17 Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University

18. Experimental Study at LNS, Tohoku Neutral Kaon Spectrometer (NKS) –The first measurement of the K 0 cross section near the threshold Published as PRC78(2008)014001 –The data prefers SLA model rather than Kaon-MAID Backward peak in cos  CM distribution NKS2 –Expanding the study using new spectrometer –Improving the acceptance K 0,  single measurement K 0  coincidence measurement –But the statistics is not enough Detector upgrade project in progress 18

19. Results of NKS The cross section of K 0 –E =0.9-1.0 and 1.0-1.1 GeV –cos  KLab = 0.9-1.0 The data prefer SLA –SLA suggests backward peak of K 0 in CM Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University forwardbackward forwardbackward 19

20. NKS to NKS2 Extending the study –We needed new spectrometer Larger acceptance better TOF resolution for the particle identification –The second generation of study by Neutral Kaon Spectrometer 2 (NKS2) 20 Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University

21. NKS NKS2 Improved Acceptance by covering forward region NKS to NKS2 21 Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University

22. Particle Identification of NKS2 An example –Liq. D 2 target –two-tracks event –TOF resolution ~350ps –opening angle cut is applied to reduce e + e - -0.9 < cos   < 0.8 22 TOF(IHL2-OHVL4) charge sign  p  

23. Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University Decay Vertex Distribution 23  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

24. Recent Results (K 0 ) 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 24 0.9<E  <1.0 [GeV] 1.0<E  <1.1 [GeV] K 0 momentum [GeV/c] d/dp [b c/GeV] 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 Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University

25. Recent Results (  )  cross-section on Liq. D 2 target –Analyzed ~30% of recorded data –+n  K 0 S + and –+p  K + + are dominant 25 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] Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University

26. 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 –Four-track-event analyses –Need to increase the acceptance Detector upgrade project is on going 26     Invariant Mass [GeV/c 2 ] p   Invariant Mass [GeV/c 2 ] all of combinations from p       event

28. The next stage of the study KY coincidence measurement –No Fermi motion correction of n in d –Reaction plane will be defined More information for study –Self polarization of  New inner detectors –to increase the acceptance Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University 28

29. Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University  Polarization Measurement Acceptance as a function of cos decay parameter 0.642(PDG) polarization pp pp t = p  × p  t  CM  pp p Transverse polarization measurement pKpK  reaction plane in CM pNpN 29

30. Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University Model Predictions:  Polarization  of Kaon in CM [degree]  Polarization SLA (rKK=-2.087) KaonMAID SA1 (P. Bydzolvski) +p  K + + +n  K 0 + calculated by P. Bydzofvky 30

32. NKS2 + Set-up with New Inner Detectors Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University A 3D tracker Vertex Drift Chamber Inner Hodoscope Upgrade project NKS2 to NKS2 + 32

33. Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University Acceptance for K 0 S +  Events The acceptance will increase with the same trigger condition –~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% Acceptance of new detectors Acceptance of Current Detectors 33

34. Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University 34 Vertex Drift Chamber Design Requirements –As possible as small cell but limited by feedthrough (3mm) –At least 6 layers with stereo wires Decision –Trapezoid (almost square) cell shape –Half cell size: 4 mm –8 layers –uu ’ vv ’ uu ’ vv ’ increasing stereo angle with radius:6.0 - 11.1° –Drift gas = Ar:Ethane(50:50) 55 mm 65 mm 137 mm uu’ vv’

35. Vertex Drift Chamber >99% tracking efficiency for each layer –by Cosmic-ray test, using Ar:Ethane (50:50) gas Position resolution: ~400 m (FWHM) Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University 35

36. Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University Event Display 36  beam

37. Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University Event Display 37  beam

39. Summary Investigation of Strangeness photoproduction –focusing on the neutral channel: +nK 0 + –near the threshold using tagged photon beam (E  =0.8-1.1GeV) Laboratory of Nuclear Science, Tohoku University KY coincidence measurement will open the next stage of the study Detector upgrade project is on going Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University 39

41. Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University 41 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] 0.0 0.5 1.0 1.0 0.5 1.0 0.5 Comparison of Acceptance 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 0.0 0.5 1.0 1.0 0.5 1.0 0.5 E  = 0.9-1.0 GeV E   =1.0-1.1 GeV NKS NKS2 543210543210 efficiency [%]

42. Masashi Kaneta: Workshop on "Hadron and Nuclear Physics (HNP09)“ Nov. 16-19, 2009, RCNP, Osaka University Figure of Merit for K 0 S +  Event Acceptance as a function of   –No drastic change Note –Vertical scale is arbitral –Please focus only the angle dependence  K in CM [degree] FoM (A.U.) four tracks pass through VDC four tracks pass through OH 42