Neutral kaon photoproduction at LNS, Tohoku Masashi Kaneta for the NKS/NKS2 collaboration Department of Physics Tohoku University International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) イントロダクション Introduction Masashi Kaneta, Tohoku Univ. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 2 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 g+n K 0+L Masashi Kaneta, Tohoku Univ. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 3 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) Masashi Kaneta, Tohoku Univ. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 4 東北大学原子核理学研究施設での実験 The Experiments at LNS, Tohoku Masashi Kaneta, Tohoku Univ. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 5 The Experiments • The series of experiments by neutral kaon spectrometer at LNS, Tohoku Univ. –The 1st 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 D2 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 2nd generation (NKS2) • • • • Constructed in 2004-2006 from scratch Commissioning run in 2006 The data taking with liquid D2 target in 2006-2007 An upgrade is on going Masashi Kaneta, Tohoku Univ. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 6 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. O. D. N. A. H. T. Chiga, B. Beckford, M. Ejima, T. Fujii, Y. Fujii, T.Fujibayashi, T. Gogami, K. Futatsukawa, Hashimoto, K. Hosomi, K. Hirose(a), A. Iguchi, S. Kameoka, H. Kanda, M. Kaneta, H. Kato, Kawama, T. Kawasaki, C. Kimura, S. Kiyokawa, T. Koike, T. Kon, Y. Ma, K. Maeda, Maruyama, A. Matsumura, Y. Miyagi, Y. Miura, K. Miwa, S.N. Nakamura, H. Nomura, Okuyama, A. Ohtani, T. Otani, M. Sato, A. Shichijo, K. Shirotori, T. Takahashi(b), Tamura, N. Taniya, H. Tsubota, K. Tsukada(c) N. Terada, M. Ukai(d), D. Uchida, 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, T. Terasawa, H. Yamazaki K. Suzuki, T. Tamae, • 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. Student (a)Now (b)Now (c)Now (d)Now name is shown with underline at LNS, Tohoku University, Japan at KEK, Japan at RIKEN, Japan at Gifu University, Japan International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 7 Tagged Photon Beam Line at LNS Neutral Kaon Neutral Kaon Spectrometer Spectrometer 2 150 MeV electron beam from LINAC Sweep magnet 1.2 GeV Stretcher-Booster Ring Masashi Kaneta, Tohoku Univ. Photon tagging system International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 8 Tagged Photon Beam at LNS g • Photon beam – Electron beam on carbon wire (11mm f) – Tagged by electron which has energy loss – Eg=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 Radiator Masashi Kaneta, Tohoku Univ. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 9 NKS • There are two arms in one dipole magnet IH: SDC: CDD: OH: EV: Inner Hodoscope Straw Drift Chamber Cylindrical Drift Chamber Outer Hodoscope Electron Veto No acceptance in forward region Masashi Kaneta, Tohoku Univ. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 10 NKS2 • 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 Masashi Kaneta, Tohoku Univ. A vertical cross section along beam International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 11 NKS2 Photo Masashi Kaneta, Tohoku Univ. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 12 Comparison of Acceptances NKS2 NKS 1.0 1.0 1.0 • Red contours: 5 cosθlab Eg = 0.9-1.0 GeV 0.5 1.0 0.5 0.5 1.0 1.0 4 – Kaon-MAID model calculation on a D2 target 3 2 – Energy threshold 0.915 GeV in g+nK0+L Eg =1.0-1.1 GeV 0.5 0.5 0.0 0.0 0.5 0.5 0.5 0.0 1.0 1.0 1 0 – Eg=0.8-1.1 GeV at LNS 0.5 efficiency [%] K 0S cross-section 1.0 K 0S momentum [GeV/c] Red contour: D2 target K 0S production cross-section (Kaon-MAID model) Gray contour: Acceptance of K 0S (p+p-) in NKS and NKS2 Masashi Kaneta, Tohoku Univ. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 13 第一世代実験 NKS の結果 Results from st the 1 generation experiment NKS Masashi Kaneta, Tohoku Univ. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 14 Particle Identification • Good pion/proton separation –DTOF: ~510ps Masashi Kaneta, Tohoku Univ. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 15 Decay Volume Cut • Main background of K 0S – e+e- from photon conversion – can be rejected by opening angle cut and Electron Veto counter p+ p- from r and w can be rejected by decay volume cut • With the decay volume cut, the S/N increased Masashi Kaneta, Tohoku Univ. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 16 Invariant Mass of p+p• After applying decay volume cut and opening angle cut (-0.9<cosqOA<0.8), invariant mass of p+ p- pair is obtained K 0S K 0S B.G.0 B.G.1 B.G.2 B.G.0: e+ e- (miss-ID as pions) B.G.1: p+ from K0S and p- from L B.G.2: p+ p- from r and w Masashi Kaneta, Tohoku Univ. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 17 Results of NKS: K 0S cross section • The first data of K 0S cross section from g+n reaction near the threshold – vertical bar: statistical error – histogram: systematic error Masashi Kaneta, Tohoku Univ. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 18 Isobar models (Effective Lagrangian Approach) • Kaon-MAID [T. Mart, C. Bennhold, PRC61 (2000) 012201(R)] – Resonances in coupling: • N(1650) S11, N(1710) P11, N(1720) P13, N(1895) D13, K *(892), K1(1270) – Reaction of input data: • K +L, K +S0, K 0S+ – including hadronic form factor and contact term • Saclay-Lyon A [T. Mizutani et al., PRC58 (1998) 75] – Resonances in coupling: • N(1720) P13, K *(892), K1(1270), L(1405) S01, L(1670) S01, L(1810) P01, S(1660) P11 – Reaction of input data: • K +L – No hadronic form factor Masashi Kaneta, Tohoku Univ. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 19 Comparison of p(g, K+)L with n(g, K0)L p(g, K+)L reaction n n(g, K0)L 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. r(K* K g) = g(K*0 K 0 g) g(K*+ K + g) r(K1 K g) : - 0.45 in Kaon-MAID from K0S+ reaction Free parameter in SLA = -1.53 r(K1K g) represented as rkk from the next slide Masashi Kaneta, Tohoku Univ. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 20 Comparison of K 0S 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 Masashi Kaneta, Tohoku Univ. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 21 What is the model suggesting? • Data prefer Saclay-Lyon A model and parametrization PH1 • In the CM frame, the angle dependence of K 0S cross sections are: backward forward backward forward Backward peak is suggested Masashi Kaneta, Tohoku Univ. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 22 第二世代実験 NKS2 の結果 Results from nd the 2 generation experiment NKS2 Masashi Kaneta, Tohoku Univ. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 23 Particle Identification – – – – Liq. D2 target two-tracks event DTOF: ~350ps opening angle cut is applied to reduce e+e- • -0.9 < cosqOA < 0.8 charge sign • An example p+ p p- TOF(IHL2-OHVL4) Masashi Kaneta, Tohoku Univ. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 24 number of counts Decay Vertex Distribution Target Cell Opening angle cut -0.9<cosqOA<0.8 is required This distribution is projected on beam axis direction Vacuum cell region • Decay vertex is reconstructed from trajectories of positive and negative charged particle pair Decay vertex point [cm] g Target Cell Masashi Kaneta, Tohoku Univ. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 25 • New region: cosqKLab<0.9 – Capability to discuss angular dependence Background is estimated by side-bands ds/dp [mb c/GeV] 0.6 0.6 0.4 0.4 0.2 0.2 0.0 0.0 -0.2 0.8 -0.2 0.8 0.6 0.6 0.4 0.4 0.2 0.2 0.0 0.0 -0.2 -0.2 1.0 1.0 0.8 0.8 0.6 0.6 0.4 0.4 0.2 0.2 0.0 0.0 -0.2 -0.2 p+p- invariant mass Masashi Kaneta, Tohoku Univ. 0.9 – 1.0 – analyzed ~30% of recorded data – g+n K 0S+L is dominant – expanding angle 1.0<Eg<1.1 [GeV] 0.8 0.8 - 0.9 0.9<Eg<1.0 [GeV] 0.8 0.7 - 0.8 • K 0S cross-section on Liq. D2 target cosKLab Recent Results (K 0) 0.0 0.2 0.4 0.6 0.0 0.2 0.4 0.6 K 0 momentum [GeV/c] International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 26 • Λ cross-section on Liq. D2 target 0.95 – 1.00 0.90 - 0.95 0.80 - 0.90 Background is estimated by side-bands 0.0 pp- invariant mass Masashi Kaneta, Tohoku Univ. 1.0<Eg<1.1 [GeV] ds/dp [mb c/GeV] – Analyzed ~30% of recorded data – g+n K 0S+L and g+p K ++L are dominant 0.9<Eg<1.0 [GeV] cosqLLab Recent Results (L) 0.2 0.4 0.6 0.8 1.0 1.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 L momentum [GeV/c] International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 27 Recent Results (cont’) • K 0 measurement – Extends the study to discuss cosq dependence – Total number of the particle is similar to NKS • L measurement – Large statistics (>10 times of NKS) – Data is from two reaction (g+p and g+n ) • need to separate to compare a model of elementally process • K +L 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 pp- invariant mass [GeV/c2] • statistics in each (Eg, p, cosq) bin are smaller.. p+p- invariant mass [GeV/c2] Masashi Kaneta, Tohoku Univ. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 28 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. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 29 Acceptance with New Detectors Note: single tracking efficiency: assumed to be 90% K 0 S (p+p- channel) L (pp- channel) (1): all K0S (p+ p- )+L(p-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 • The acceptance will increase – ~8 times Masashi Kaneta, Tohoku Univ. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 30 New Inner Detectors Photo taken in Nov. 2008 Masashi Kaneta, Tohoku Univ. Vertex Drift Chmaber 8 Layers u,u’,v,v’,u,u’,v,v’ structure International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 31 Event Display from the Last Run • Chamber commissioning and trigger study runs are held Sep. and Nov. 2008 g beam Masashi Kaneta, Tohoku Univ. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 32 Event Display from the Last Run • Chamber commissioning and trigger study runs are held Sep. and Nov. 2008 g beam Masashi Kaneta, Tohoku Univ. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 33 Summary • The investigation of neutral kaon photoproduction at LNS, Tohoku – Tagged photon beam (Eg=0.8-1.1 GeV)at LNS, Tohoku • The first measurement of neutral kaon via g+n reaction near the threshold by NKS – Carbon target: PLB651(2007)269 – Liquid D2 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. International Symposium on Strangeness in Nuclear and Hadronic Systems -SENDAI08- (Dec15-18) 34
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