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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

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. Contents. Introduction SksMinus components Veto counters for beam decay events

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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

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

  3. Introduction The E13 experiment SksMinus setup

  4. J-PARC E13 experiment Hypernuclear g-ray spectroscopy experiments on several light nuclei (4LHe, 7LLi, 10LB, 11LB, 19LF) (K-, p- ) reaction @ pK = 1.5 GeV/c • Reaction analysis : K1.8 + SksMinus • g-ray detection : Hyperball-J ⇒Reaction-g coincidence JPS Meeting 2008 Yamagata K. Shirotori

  5. SksMinus setup Requirements for p- of ~1.4 GeV/c • Acceptance >100 msr, ~20o scattering angles • Momentum resolution < 3 MeV/c (FWHM) SksMinus SksMinus elements • Particle tracking : SDC1~4 • Time-of-flight : STOF • Reaction ID : BAC, SAC (n=1.03) • Veto counters SMF : m- from K- → m- + n SP0 : p- from K- → p- + p0 • Target : Li2O, Teflon ((CF2)n), Boron(10,11B) (~10 cm, ~15 g/cm2) Liquid 4He (25 cm, 3.13 g/cm2) _ 1 m JPS Meeting 2008 Yamagata K. Shirotori

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

  7. Beam decay events BAC SAC BAC SAC Target Target p- m- K- K- _ n Reaction Decay Cannot be distinguished Huge trigger rate Missing mass background _ K- → m- n (63.4%) ⇒Muon filter (SMF) K- → p- p0 (21.1%) ⇒Pi zero veto (SP0) Simulation JPS Meeting 2008 Yamagata K. Shirotori

  8. Scintillator g Side view K- p- g Target region Lead SP0 (Pi zero veto) : specifications g rays detected by shower counter (Lead converter) To distinguish between • Beam decay : K-→p-p0 • L decay : N+L→N+N (NMWD) ⇒Number of hit layers >=3 K-→ p-p0 → g g Layer multiplicity (200 MeV/c Neutron) Layer multiplicity (p0) Simulation Simulation 0.2% 84% JPS Meeting 2008 Yamagata K. Shirotori 3 3 Number of hit layers Number of hit layers

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

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

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

  12. Liquid 4He target 4LHe experiment ⇒Charge symmetry breaking (4LH ⇔4LHe)

  13. 4He target (Designed by S. Ishimoto) 300 mm Beam size : sx~26 mm, sy~4 mm • Target cell size : f120 mm×250 mm (2.7L) (outer cell f210×330) • Size fit to the inner space of Hyperball-J • Cooling power : 1.5 W @ 4 K Refrigerator Hyperball-J frame He pipe (Cu) Outer cell (Al) Target cell Mylar K- Mylar Target cell (SUS) p- JPS Meeting 2008 Yamagata K. Shirotori Radiative heat shield (Al) 100 mm

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

  15. Other detectors and Summary

  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 JPS Meeting 2008 Yamagata K. Shirotori

  17. Summary • J-PARC E13 experiment via the (K-, p-) reaction with pK =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 • 4He target • Under construction with S. Ishimoto • Other detectors being prepared on schedule The experiment is scheduled in 2009. JPS Meeting 2008 Yamagata K. Shirotori

  18. JPS Meeting 2008 Yamagata K. Shirotori

  19. Backup

  20. Beam Momentum K- + n -> L + p- JPS Meeting 2008 Yamagata K. Shirotori

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

  22. Motivation : Charge symmetry breaking Old data suggest large charge symmetry breaking in LN interaction. 4LH ⇔ 4LHe (Ln ⇔ Lp) • Mass difference : S+, S0, S-. Statistics of old g-ray data is poor, in particular 4LHe(1+→0+) data. PL83B(1979)252 Hyperfragment (Stop K- reaction) + NaI detector → In-flight (K-, p-) reaction + Ge detector Doppler shift correction & Low background JPS Meeting 2008 Yamagata K. Shirotori

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

  24. The modification of SKS Present SKS 2.2T 2.7T q~20° q~20° 1.05 GeV/c (p+, K+) reaction (K+ 0.72 GeV/c) • Scattered particles are not focused and present drift chambers (SDC3,4) are small for large reaction angle (half acceptance). 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. q~20° JPS Meeting 2008 Yamagata K. Shirotori

  26. Simulation results of acceptance and momentum resolution Simulation Simulation • 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) JPS Meeting 2008 Yamagata K. Shirotori

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

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

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

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

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

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

  33. SksMinus setup Requirements for p- of ~1.4 GeV/c • Acceptance >100 msr, ~20o scattering angles • Momentum resolution < 3 MeV/c (FWHM) SksMinus elements • Particle tracking : SDC1~4 • Time-of-flight : STOF • Reaction ID : BAC, SAC (n=1.03) • Veto counters SMF : m- from K- → m- + n SP0 : p- from K- → p- + p0 • Target : Li2O, Teflon, Boron(10,11B) (~10 cm, ~15 g/cm2) Liquid 4He (25 cm, 3.13 g/cm2) SKS _ K- JPS Meeting 2008 Yamagata K. Shirotori

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