1 / 23

J-PARC における 4 L He の生成と構造の研究

J-PARC における 4 L He の生成と構造の研究. 東北大学 大学院理学研究科 白鳥昂太郎 for the Hyperball-J Collaboration. Contents. E13 at J-PARC Physics motivation Setup : SksMinus Yield estimate Summary. Day-1 experiment E13 at J-PARC. Hypernuclear g -ray spectroscopy experiment.

cwill
Download Presentation

J-PARC における 4 L He の生成と構造の研究

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. J-PARCにおける4LHeの生成と構造の研究 東北大学 大学院理学研究科 白鳥昂太郎 for the Hyperball-J Collaboration

  2. Contents • E13 atJ-PARC • Physics motivation • Setup : SksMinus • Yield estimate • Summary 2007 JPS in Tokyo Metropolitan University

  3. Day-1 experiment E13 at J-PARC Hypernuclear g-ray spectroscopy experiment • Spin-flip B(M1) measurement and gLin a nucleus (7LLi) • LN interaction study from p-shell hypernuclei (10LB and 11LB) • Radial dependence of LN interaction from sd-shell hypernuclei (19LF) • Charge symmetry breaking of LN interaction and Spin-flip property in hypernuclear production (4LHe) 2007 JPS in Tokyo Metropolitan University

  4. Motivation (1): 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 2007 JPS in Tokyo Metropolitan University

  5. Motivation (2): Spin-flip property Spin-flip property of L hypernuclear production (4LHe(1+)) • Confirm spin-flip cross sections • Study of baryon production in nuclei Beam momentum 1.1-1.8 GeV/c 4LHe(0+) 4LHe(1+) Spin-flip by K* exchange Elementary process K- + n -> L + p- • g-ray spectroscopy is the only way to measure the spin-flip state. • Excitation energy ~1MeV • ⇔ Magnetic spectrometer resolution • ~2 MeV 2007 JPS in Tokyo Metropolitan University G. P. Gopal et al., NPB119(1977)362, T. Harada priv. comm.

  6. Setup at the K1.8 beam line 4He (K-, p-g) 4LHe • (K-, p- ) reaction analysis: K1.8 + SksMinus • g-ray measurement: Hyperball-J (6 % efficiency @ 1 MeV) • Liquid 4He target (25 cm, 3.13 g/cm2) Beam momentum: 1.5 GeV/c Spin-flip measurement: 1.1-1.8 GeV/c 2007 JPS in Tokyo Metropolitan University

  7. SksMinus setup Requirements for p- of 1.4 GeV/c • Acceptance >100 msr, ~20o scattering angles • Momentum resolution < 3 MeV/c (FWHM) SksMinus • SDC1~4 : Particle tracking • STOF : Time-of-flight • SAC : K- beam veto (n=1.03) • (SFV : K- beam veto) Background Veto _ • SMF : m- from K- → m- + n • SP0 : p- from K- → p- + p0 2007 JPS in Tokyo Metropolitan University

  8. SksMinus basic performance • Acceptance is optimized for (K-, p- ) reaction @ pK=1.5 GeV/c. Sufficient for 1.0~1.7 GeV/c p- Covering scattering angle up to 20o • Momentum resolution < 3 MeV/c (FWHM) • PID counters: STOF, SAC (n=1.03) p- momentum [MeV/c] 2.7 T: pp = 1.1~1.7 GeV/c (pK = 1.2~1.8 GeV/c) (2.2 T: pp < 1.1 GeV/c (pK < 1.2 GeV/c)) 2007 JPS in Tokyo Metropolitan University

  9. Decay veto counters Decay veto counters are optimized for 1.5 GeV/c beam condition. SMF SP0 p- (stopped in the iron) m- (passing through) Decay veto counters will be used without changing the setup. 2007 JPS in Tokyo Metropolitan University

  10. Decay veto counters: performance Performance of SP0 Performance of SMF p- rejection ~78% @ 1.5 GeV/c Kinematical region of p- only overlaps less than 3o. 1.1 GeV/c 1.3 GeV/c p m 1.5 GeV/c 1.8 GeV/c W/o veto counters m stopping points follow the same distribution. Trigger rate ~600 /spill @ 1.5 GeV/c (~2000 /spill @ 1.8 GeV/c) • m events are greatly reduced in offline analysis @ 1.5 GeV/c. • m- rejection >99% 2007 JPS in Tokyo Metropolitan University

  11. Yield estimate Tracking eff = 0.6 Ge live time = 0.7 eg = 0.06 @ 1 MeV * seff : Cross section corrected by acceptance ~200 hours for total beam time 2007 JPS in Tokyo Metropolitan University

  12. Summary • 4LHe study in Day-1 g-ray spectroscopy experiment Charge symmetry breaking in LN interaction Spin-flip property of L hypernuclear production • SksMinus is designed for (K-, p-) reaction at pK=1.1~1.8 GeV/c. One configuration for all beam momentum Sufficient acceptance (>100 msr @ 1.0~1.7 GeV/c) • Total beam time of ~200 hours necessary for ~200 counts per each momentum 2007 JPS in Tokyo Metropolitan University

  13. Backup

  14. Experimental advantages • g-ray spectroscopy is the only way to measure the spin-flip state. • Excitation energy ~1MeV ⇔ Magnetic spectrometer resolution ~2 MeV • → It is difficult to resolve the spin-flip state. Advantages for g-ray measurement Early experiment (by NaI detector) Hyperfragment (Stop K- reaction) + Identification via weak decay products • Large momentum transfer + Recoil momentum direction cannot be measured. ×Doppler shift correction = broad peak • Many background events Low sensitivity This experiment (by Ge detector) In-flight (K-, p-) reaction Doppler shift correction + Low background 2007 JPS in Tokyo Metropolitan University

  15. Cross section of 4LHe(1+)&(0+) 2007 JPS in Tokyo Metropolitan University

  16. Particle identification • (K-, p- ) → p- or K- • Beam K- can greatly be decreased by SAC (n=1.03) and SFV • → less than 30 trigger /spill (500 k/spill beam) • Time resolution of STOF ~150 ps (rms) • For B(M1) measurement, dual SAC is planned because of saving forward events. 2007 JPS in Tokyo Metropolitan University

  17. Target 20cm BAC SAC m Beam K Decay n Background events : Beam decay • Trigger rate • Missing mass _ _ • K- → m-n (63.4%) (1390 /spill) ⇒Muon Filter • K- → p- p0 (21.1%) (350 /spill) ⇒PiZero Veto Fake trigger ~1940 /spill True event trigger ~600 /spill (Contribution of three-body decay ~200 /spill) 2007 JPS in Tokyo Metropolitan University

  18. Muon Filter -SMF- performance Stopping/absorption points • Rejected m : 86% • Non-rejected (stopped in the iron) → offline analysis >99% • Over kill for true π ~2.5% Target Non-rejected Rejected STOF SMF SKS magnet Iron 2007 JPS in Tokyo Metropolitan University

  19. PiZero veto -SP0- Acceptance 85% 78% of p-p0 events rejected 6 sets of 5 mm lead plate and 10 mm scintillation counter layer at 1.5 GeV/c beam. 2007 JPS in Tokyo Metropolitan University

  20. 3-body Decay K-→π-π-π+ (5.58%) K-→e-π0ν (4.87%) K-→μ-π0ν (3.27%) K-→π-π0π0 (1.73%) 2007 JPS in Tokyo Metropolitan University

  21. Background rejection and trigger rate • (K-,π-) Reaction rate : 600 ⇒ ~570 • K-→m- n : 1390 ⇒ ~190 • K-→p- p0 : 350 ⇒ ~80 • K- Beam : ~30 • 3-body decay : 200 ⇒ ~70 • Total : 2570 (1940) ⇒ 940 (340) /spill Total trigger is reduced by Ge trigger ~1/2. ~470/spill w/ Ge trigger decay decay Comparable to the present trigger rate Offline analysis 7LLi bound states 2007 JPS in Tokyo Metropolitan University

  22. Background rejection and trigger rate • (K-,π-) Reaction rate : 600 ⇒ ~570 • K-→m- n : 1390 ⇒ ~190 • K-→p- p0 : 350 ⇒ ~80 • K- Beam : ~30 • 3-body decay : 200 ⇒ ~70 • Total : 2570 (1940) ⇒ 940 (340) /spill Total trigger is reduced by Ge trigger ~1/2. ~470/spill w/ Ge trigger decay decay Comparable to the present trigger rate Offline analysis 7LLi bound states 2007 JPS in Tokyo Metropolitan University

  23. How about 4LH ? • g ray from 4LH by (K-, p0) tagging by SP0 ? (To detect no charged particle events ?) 2007 JPS in Tokyo Metropolitan University

More Related