Investigation of Strangeness Photo-Production near the Threshold Masashi Kaneta for the NKS2 collaboration Department of Physics, Tohoku University

2 Questions

3 Q. 1 You are: (1) an under graduate student, (2) a master course student, (3) a doctor course student, or (4) not a student

4 Q. 2 Have you ever taken a class of nuclear physics?

5 Q. 3 Do you think that QCD can calculate everything of hadron?

6 Quark StarNeutron Star Stars compression phase transition QCD Phase Diagram Baryon density Baryon Big bang Temperature Quark-Gluon Plasma (QGP) phase cooling element synthesis 0 Meson phase transition Color superconductivity? Our world Neutron Star Hadron Phase

LHCCERN 7 Quark StarNeutron Star Stars compression phase transition Accelerators and Facilities Baryon density Baryon Big bang Temperature Quark-Gluon Plasma (QGP) phase cooling element synthesis 0 Meson phase transition Color superconductivity? Our world Neutron Star Hadron Phase JLab RCNP Osaka U. ELPH Tohoku U. RIBFRIKEN FAIRGSI J-PARC Spring-8 SISGSI AGSBNL SPSCERN RHICBNL LHCCERN SIS 200/300 GSI AGS J-PARC Beam Ion Hadron Photon

LHCCERN 8 Quark StarNeutron Star Stars compression phase transition My Phase Shift (Transition?) Baryon density Baryon Big bang Temperature Quark-Gluon Plasma (QGP) phase cooling element synthesis 0 Meson phase transition Color superconductivity? Our world Neutron Star Hadron Phase SPSCERN Graduate student of Hiroshima Univ.

9 Pictures of NA44 Era

LHCCERN 10 Quark StarNeutron Star Stars compression phase transition My Phase Shift (Transition?) Baryon density Baryon Big bang Temperature Quark-Gluon Plasma (QGP) phase cooling element synthesis 0 Meson phase transition Color superconductivity? Our world Neutron Star Hadron Phase SPSCERN RHICBNL ELPH Tohoku U PostDoc of LBNL and RIKEN-BNL Research Center

, RNC Group, LBNL 2004, RBRC Chirstman Party hosted by T.D. Lee

LHCCERN 12 Quark StarNeutron Star Stars compression phase transition My Phase Shift (Transition?) Baryon density Baryon Big bang Temperature Quark-Gluon Plasma (QGP) phase cooling element synthesis 0 Meson phase transition Color superconductivity? Our world Neutron Star Hadron Phase SPSCERN RHICBNL JLab ELPH Tohoku U Present Assistant Prof. of Tohoku Univ.

13 Outlook of This Talk

INTRODUCTION 序 14

15 General aim –Understanding the mechanism of strangeness production Reaction –hadron-hadron –gamma-nucleaon Missing resonance search w/ energy scan Characteristics of our experiment –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 Strangeness Photo-production

16 +N K+Y+N K+Y

17  +p  K + +   threshold: MeV   +p  K + +  0  threshold: MeV   +p  K 0 +  +  threshold: MeV   +n  K 0 +   threshold: MeV   +n  K 0 +  0  threshold: MeV   +n  K + +  -  threshold: MeV 

Data in the Market +nK0++nK0+ +nK++-+nK++- +nK0+0+nK0+0 LEPS experiment: differencial cross section in E= GeV with polarized photon beam PRL97 (2006) NKS experiment: differencial cross section in E= GeV PRC78(2008) CLAS experiment: differencial cross section in E= GeV PLB688(2010)289 +pK0+++pK0++ Phys.Rev.C73(2006) Phys.Lett.B464(1999)331 SAPHIR 18 +pK+++pK++ +pK+++pK++

Experiments to investigate Strangeness Photo-Production at LNS/ELPH, Tohoku Univ. 19

: Using TAGX spectrometer Reconstruct K 0 S from  +  - decay The first measurement of K 0 cross section from nK 0 + reaction [Phys.Rev.C78(2008)014001] Neutral Kaon Spectrometer 20 Experiments to investigate Strangeness Photo-Production at LNS/ELPH, Tohoku Univ.

2005 Construction of new spectrometer Data taking Upgrade inner detectors 2010 Data taking 21 Experiments to investigate Strangeness Photo-Production at LNS/ELPH, Tohoku Univ.

22 The NKS2 Collaboration Department of Physics, Tohoku University B. Beckford, T. Fujii, Y. Fujii, T.Fujibayashi, K. Futatsukawa, O. Hashimoto, A. Iguchi, H. Kanda, Kaneko, M. Kaneta, T. Kawasaki, C. Kimura, S. Kiyokawa, T. Koike, K. Maeda, N. Maruyama, Matsubara, Y. Miyagi, K. Miwa, S.N. Nakamura, A. Okuyama, H. Tamura, K. Tsukada, N. Terada, F. Yamamoto Research Center of Electron-Photon Science, Tohoku University K. Hirose, T. Ishikawa, T. Tamae, H. Yamazaki Department of Nuclear Science, Lanzhou University, Lanzhou, China Y.C. Han, T.S. Wang Nuclear Institute, Czech Republic P. Bydzovsky, M. Sotona 博士課程前期 ( 修士で卒業 ) 博士課程後期 (Dr.Sc. を所得 )

EXPERIMENT 実験 23

24 青葉山キャンパス 電子光理学研究センター Research Center of Electron-Photon Science (ELPH), Tohoku Univ. Linac (Max 200 MeV) Stretcher Booster Ring (Max 1.2 GeV)

25 BM4 tagger BM5 tagger to the GeV  experimental hall NKS2 Radiator (Carbon wire) to make Bremsstrahlung B Photon Beam Orbit electron (1.2 GeV) Scattered electron ( GeV) Tag F Tag B Sweep magnet Photon Beam line – top view – top view

26  beam vacuum of STB-ring Collimator Rejection of beam halo Sweep Magnet Rejection of e + e - Dipole Magnet Target System Making of liq. D 2 target Vacuum Region Suppress of pair creation Liquid D 2 Target Lead glass counter Measurement of tagging efficiency Photon Beam line – side view – side view BPM

27 NKS2 Detector Setup 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

28 NKS NKS2

29  +d  K 0 +  +(p) K 0 S   + +       p Reaction Decay Mode Trigger Photon: Tagger hit 2 charged particle: nHit on IH2 and nHit on OH2 Background rejection: Veto of e  from upstream Trigger rate: ~1 kHz at 2 MHz tagger rate DAQ efficiency ~70%

RECENT RESULTS 最近の結果 30

31 Particle Identification 1/ charge×momentum [GeV/c] Mass square [GeV 2 /c 4 ]   p d  p d

32 Background Rejection - decay volume cut Target cell No cut Decay vertex resolution 1.1mm for horizontal 4.2mm for vertical

33 Invariant Mass Distributions

34 Error bars : statistical only Differential Cross Section E  = 0.90 – 1.00 GeV E  = 1.00 – 1.08 GeV d  /dp Lab [  b/(GeV/c)] p Lab [GeV/c]  + d  K 0 + X (mainly  + n  K 0 +  )

Error bars : statistical only E  = 0.90 – 1.00 GeV E  = 1.00 – 1.08 GeV d  /dp Lab [  b/(GeV/c)] p Lab [GeV/c] 35 Differential Cross Section  + d   + X (mainly  + n  K 0 +  and  + p  K + +  )

COMPARISON WITH MODELS モデルとの比較 36

Models near the threshold Effective Lagrangian Approach also knows as Isobar model 37 Rigge Plus Resonance Model

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    N N N K K K s channel t channel u channel Y N N *   * K,K *,K 1 Y Y YY*YY*  N K Contact term Y 38 0.45 in Kaon-MAID, estimated from pK 0  + data Free parameter in Saclay-Lyon A However, the decay width of K 1 resonance is not known

Characteristics of K  Channel - comparison with K  - comparison with K  39  N K Y s channel In the s-channel exchange, K  : N* K  : N* and  *

Characteristics of K 0  Channel - comparison with K   40  N K t channel Y  N K u channel Y  N K Y s channel No contribution of charge term in coupling constants

Models Kaon-MAID –T.Mart, C.Bennhold –PRC61 (2000) (R) Saclay-Lyon A –T. Mizutani et al. –PRC58 (1998) Kaon -MAID Saclay -Lyon A Input data pK +  ○○ pK +  0 ○ pK 0  + ○ Resonances included in the model N (1650) S 11 ○ N (1710) P 11 ○ N (1720) P 13 ○○  (1900) S 31 ○  (1910) P 31 ○ K* (892) ○○ K 1 (1270) ○○  (1405) ○  (1670) ○  (1810) ○  (1660) ○ Hadronic form factor ○ contact term ○

42 Error bars : statistical only Comparison with Isobar Models d  /dp Lab [  b/(GeV/c)] p Lab [GeV/c]  + d  K 0 + X, E  = 0.90 – 1.00 GeV Kaon-MAID All K 0  K 0  0 K 0  + Saclay-Lyon A rkk = -1.0 rkk = -1.5 rkk = -2.0 Kaon-MAID  All

43 d  /dp Lab [  b/(GeV/c)] p Lab [GeV/c] Kaon-MAID All K 0  K 0  0 K 0  + Saclay-Lyon A rkk = -1.0 rkk = -1.5 rkk = -2.0 Kaon-MAID  All Comparison with Isobar Models  + d  K 0 + X, E  = 1.08 – 1.08 GeV Error bars : statistical only

Invariant Amplitude M = M background (Regge) +  M s (Isobar) Phys.Rev.C T. Corthals et al. 44 Regge Plus Resonance (RPR) Model  N K Y s channel N(1650) S 11, N(1710) P 11 N(1720)P 13, N(1720) P 13 N(1900) D 13 (1900) S 31 (1910) P 31 K*(892) Trajectory K(494) Trajectory  (t) t [GeV/c 2 ]

Calculation of RPR Model E  = GeV, cos  K0 Lab = Nucleon Resonances in the K  process N (1650) S 11, N (1710) P 11, N (1720) P 13, N (1900) P 11, N (1900) D 13 N (1900) D 13 : Missing Resonance No data to helicity amplitude of N (1900) D 13 → From -2.0 To 2.0 (Cyan Line 0.0) P.Vancraeyveld et al.: private communication Our results are two times larger than the calculations of RPR at least 45 Comparison with RPR Model

46 K 0  : Backward Distributions (fitting results) K +  : Forward Distributions (SAPHIR, CLAS) SAPHIR: K. H. Glander et al., Eur. Phys. J., A19:251–273, CLAS: R. Bradford et al., Phys. Rev., C73:035202, Kaon Angle distribution in CM

SUMMARY まとめ 47

48 Investigating strangeness photo-production via  + n  K 0 S +  channel using the NKS2 spectrometer at ELPH, Tohoku Univ. Differential cross sections of K 0 S and  in  +d K 0 S Larger angle coverage than previous experiment  The first measurement K 0 S +  total cross section estimated similar shape to K + +  as a function of E  Suggestion from comparison of data with models Angular distribution backward enhance in K 0 S +  ( K + + : slightly forward peak) Detector upgrade was done and we took new data

49 Upgrade Project To increase acceptance Inner detectors are replaced by Vertex Drift Chamber (VDC) New Inner Hodoscope (IH)

50VDCIH

BACK UP 予備 51

52  1 m Drift chambers CDC: Honeycomb cell SDC: Straw Drift chamber Counters Inner and Outer Hodoscope Electron Veto  beam Detector Setup

Results of NKS 53

Suggestion from NKS Results backward angular distribution in CM 54

E  [GeV] +n K0++n K0+  [b] 10 5 Saclay-Lyon A Kaon-MAID 0.9 Suggestion from NKS Results before after 55

NKS NKS2 Improved Acceptance by covering forward region NKS to NKS2 56

57 Error bars : statistical only Comparison with Isobar Models  + d   + X E  = 0.90 – 1.00 GeV E  = 1.00 – 1.08 GeV d  /dp Lab [  b/(GeV/c)] p Lab [GeV/c] Saclay-Lyon A rkk = -1.0 rkk = -1.5 rkk = -2.0 Kaon-MAID  All

58 Integral Cross Section : Inclusive  Integral Region : cos   Lab = Error : statistical error Systematic Uncertainty : < 14 %

59 [1] K. H. Glander et al., Eur. Phys. J., A19:251–273, [2] M. Q. Tran et al., Phys. Lett., B445:20–26, Total Cross Section  +d  K + +  +n Estimated

Strange TDC distribution 0xFxxxx is continued in negative region as accidental coincidence distribution The module recorded hit after common stop –Program is needed to be modified When this range is treated as negative value We found that there are many hits in unexpected TDC range Negative value hit time after common stop 60

Beam Test in 2010/4/26-28 Changing TDC module parameters –Set a time window not to measure a time after Common Stop –One trigger configuration was tested (as the result) Test was terminated due to a wire broken Original Set a time window Red and Blue: different time window 61

Beam Test in 2010/ ６ /1-4 Trigger Combination Check –w/ or w/o Electron Veto Counter in downstream region –To be biased or not to be –At ~2MHz beam rate, DAQ efficiency is ~65% (same order with run-2007) Now, 29 AMT-VME boards It was 21 in 2007 Test for reducing number of TDC modules –How effective to increase number of DAQ PC –results: about 1.15 times better at 2.0MHz beam rate 62