1. J-PARC でのハイパー核ガンマ線分光実験用 散乱粒子磁気スペクトロメータ検出器の準備 状況 東北大理, 岐阜大教 A, KEK B 白鳥昂太郎, 田村裕和, 鵜養美冬 A, 石元茂 B, 大谷友和, 小池武志, 佐藤美沙子, 千賀信幸, 細見健二, 馬越, 三輪浩司, 山本剛史, 他 Hyperball-J collaboration

2. JPS Meeting 2008 Yamagata K. Shirotori 2 Contents  Introduction  SksMinus components Veto counters for beam decay events 4 He target Other detectors  Summary

3. Introduction  The E13 experiment  SksMinus setup

4. JPS Meeting 2008 Yamagata K. Shirotori 4  Reaction analysis : K1.8 + SksMinus   -ray detection : Hyperball-J ⇒ Reaction-  coincidence J-PARC E13 experiment Hypernuclear  -ray spectroscopy experiments on several light nuclei ( 4  He, 7  Li, 10  B, 11  B, 19  F) (K -,  - ) reaction @ p K = 1.5 GeV/c

5. JPS Meeting 2008 Yamagata K. Shirotori 5 SksMinus setup SksMinus elements  Particle tracking : SDC1~4  Time-of-flight : STOF  Reaction ID : BAC, SAC (n=1.03)  Veto counters SMF :  - from K - →  - + SP0 :  - from K - →  - +  0  Target : Li 2 O, Teflon ((CF2) n ), Boron( 10,11 B) (~10 cm, ~15 g/cm 2 ) Liquid 4 He (25 cm, 3.13 g/cm 2 ) _ Requirements for  - of ~1.4 GeV/c Acceptance >100 msr, ~20 o scattering angles Momentum resolution < 3 MeV/c (FWHM) 1 m SksMinus

6. Veto counters for beam decay events  SP0 : Pi zero veto

7. JPS Meeting 2008 Yamagata K. Shirotori 7 Beam decay events K - →  - (63.4%) ⇒ Muon filter (SMF) K - →  -  0 (21.1%) ⇒ Pi zero veto (SP0) _ K-K- BACSAC Target  Reaction K-K- BACSAC Target  Decay Cannot be distinguished _ Huge trigger rate Missing mass background Simulation

8. JPS Meeting 2008 Yamagata K. Shirotori 8 Side view Scintillator Lead Target region   K-K- -- SP0 (Pi zero veto) : specifications 84% Layer multiplicity  0 ) K - →  -  0 →  Number of hit layers  rays detected by shower counter (Lead converter) To distinguish between  Beam decay : K - →  -  0   decay : N+  →N+N (NMWD) ⇒ Number of hit layers >=3 0.2% Number of hit layers Simulation 3 3 Layer multiplicity  200 MeV/c Neutron)

9. JPS Meeting 2008 Yamagata K. Shirotori 9 SP0 (Pi zero veto) : test experiment e + beam test experiment at Tohoku-LNS @ 100-300 MeV ⇒ Response is consistent with Geant4 simulation. ⇒ Neutron beam test experiment at Tohoku-CYRIC (planned) e+e+  Layer multiplicity  e + ) Event display Pb Plastic Scintillator Sideview e+e+ Finger Counter

10. JPS Meeting 2008 Yamagata K. Shirotori 10 SP0 (Pi zero veto) : design Aluminum Spacer Lead Plastic scintillator SP0 design based on the range counter (KEK E559) Full assembly 1352 mm 1816 mm 400 mm 170 mm 14 mm

11. JPS Meeting 2008 Yamagata K. Shirotori 11 SP0 (Pi zero veto) : design Aluminum Spacer Lead Plastic scintillator SP0 design based on the range counter (KEK E559) 1352 mm 1816 mm 400 mm 170 mm Hyperball-J SDC1 SKS magnet SDC2 SP0 K-K- Around Pi zero veto 500 mm

12. Liquid 4 He target 4  He experiment ⇒ Charge symmetry breaking ( 4  H ⇔ 4  He)

13. JPS Meeting 2008 Yamagata K. Shirotori 13 4 He target (Designed by S. Ishimoto) Beam size :  x ~26 mm,  y ~4 mm  Target cell size :  120 mm×250 mm (2.7L) (outer cell  210×330) Size fit to the inner space of Hyperball-J  Cooling power : 1.5 W @ 4 K Hyperball-J frame K-K- -- Refrigerator Target cell Target cell (SUS) 300 mm Mylar 100 mm Radiative heat shield (Al) He pipe (Cu) Outer cell (Al)

14. JPS Meeting 2008 Yamagata K. Shirotori 14 Around the target Tight space around the target ⇒ Optimal detector arrangement for the 4  He experiment BAC K-K- SAC -- PWO Refrigerator Target PMT Magnetic shield PWO Target PWO 210 mm 100 mm

15. Other detectors and Summary

16. JPS Meeting 2008 Yamagata K. Shirotori 16 Other detectors  Drift chamber SDC2 : Test and repair in Tohoku Univ. SDC3&4 : Ready (SDC1 : J-PARC E05 experiment)  Aerogel Cherenkov counter SAC, BAC : Basic design finalized  TOF counter Existing SKS TOF counter + additional scintillation counter  Muon filter Iron block + scintillation counter = Existing things

17. JPS Meeting 2008 Yamagata K. Shirotori 17 Summary  J-PARC E13 experiment via the (K -,  - ) reaction with p K =1.5 GeV/c Magnetic spectrometer, SksMinus and Hyperball-J  Preparation of SksMinus detectors Veto counters for beam decay events  Pi zero veto and Muon filter 4 He target  Under construction with S. Ishimoto Other detectors being prepared on schedule The experiment is scheduled in 2009.

18. JPS Meeting 2008 Yamagata K. Shirotori 18

19. Backup

20. JPS Meeting 2008 Yamagata K. Shirotori 20 Beam Momentum    n  

21. JPS Meeting 2008 Yamagata K. Shirotori 21 Calculated cross section for 7  Li

22. JPS Meeting 2008 Yamagata K. Shirotori 22 Motivation : Charge symmetry breaking  Mass difference :  +  0  -. Statistics of old  -ray data is poor, in particular 4  He(1 + →0 + ) data. Old data suggest large charge symmetry breaking in  N interaction. 4  H ⇔ 4  He (  n ⇔  p) PL83B(1979)252 Hyperfragment (Stop K - reaction) + NaI detector → In-flight (K -,  - ) reaction + Ge detector Doppler shift correction & Low background

23. JPS Meeting 2008 Yamagata K. Shirotori 23 Cross section of 4  He(1 + )&(0 + )

24. JPS Meeting 2008 Yamagata K. Shirotori 24 The modification of SKS Momentum resolution 0.1%FWHM (0.72 MeV/c) @ 720 MeV/c, 2.2T Maximum central momentum 1.0 GeV/c @ 2.7T Acceptance100 msr @ 0.72GeV/c 2.2T2.7T  ~20°  Scattered particles are not focused and present drift chambers (SDC3,4) are small for large reaction angle (half acceptance). 1.05 GeV/c (  +, K + ) reaction (K + 0.72 GeV/c) Present SKS

25. JPS Meeting 2008 Yamagata K. Shirotori 25 The modification of SKS  Keeping large acceptance and wide angular coverage by large drift chambers (2m×1m) (from BNL and Freiburg)  Incident beam angle and position of drift chambers are optimized by keeping acceptance for the 1.5 GeV/c beam condition.  Setup can be used for 1.1~1.8 GeV/c beam hypernuclear gamma ray spectroscopy experiment without modification.  ~20°

26. JPS Meeting 2008 Yamagata K. Shirotori 26 Simulation results of acceptance and momentum resolution  Acceptance at 1.4 GeV/c, ~130 msr  Enough angular acceptance, ~20 degree  Momentum resolution at 1.4 GeV/c ~2.1 MeV/c (FWHM) Simulation

27. JPS Meeting 2008 Yamagata K. Shirotori 27 Particle identification  (K -,  - ) →  - or K - Beam K- can greatly be decreased by SAC (n=1.03)  Time resolution of STOF ~150 ps (rms) Simulation

28. JPS Meeting 2008 Yamagata K. Shirotori 28 Assumed Gaussian distribution  x ~26.0 mm  y ~4.0 mm  (dx/dz) ~20 mrad (1.1°)  (dy/dz) ~2 mrad (0.1°) xy Beam profile

29. JPS Meeting 2008 Yamagata K. Shirotori 29 Muon filter : SMF  - (through)  - (Absorbed in iron) SMF Stopping/absorption points Simulation

30. JPS Meeting 2008 Yamagata K. Shirotori 30 Muon filter : SMF  - (through)  - (Absorbed in iron) SMF Stopping/absorption points Simulation

31. JPS Meeting 2008 Yamagata K. Shirotori 31 Muon filter : SMF ~88%  - detected at the trigger level >99%  - detected by tracking analysis (  - miss-ID ~2%) Stopping/absorption points -- -- X Z Simulation

32. JPS Meeting 2008 Yamagata K. Shirotori 32 Energy deposit of Miss-ID  -  - : 1.51 %  - : 0.32 % e - /e + : 0.47 %  : 1.29 % p/n : 0.17 % others : 0.16 %  - miss-ID ~2% ⇒ E th > 2 MeV Simulation

33. JPS Meeting 2008 Yamagata K. Shirotori 33 SksMinus setup SksMinus elements  Particle tracking : SDC1~4  Time-of-flight : STOF  Reaction ID : BAC, SAC (n=1.03)  Veto counters SMF :  - from K - →  - + SP0 :  - from K - →  - +  0  Target : Li 2 O, Teflon, Boron( 10,11 B) (~10 cm, ~15 g/cm 2 ) Liquid 4 He (25 cm, 3.13 g/cm 2 ) _ Requirements for  - of ~1.4 GeV/c Acceptance >100 msr, ~20 o scattering angles Momentum resolution < 3 MeV/c (FWHM) SKS K-K-