Future gamma-ray spectroscopic experiment (J-PARC E63) on 4 ΛH

Transcription

1 Future gamma-ray spectroscopic experiment (J-PARC E63) on ΛH 2018/6/26 T. O. Yamamoto KEK IPNS (Japan) for the E63 collaboration

2 Contents CSB in s-shell hypernuclear system studied via γ-ray spectroscopy γ-ray spectroscopy on ΛHe (J-PARC E13) Next step: γ-ray spectroscopy on ΛH (J-PARC E63) Previous studies on ΛH Strategy of new measurement Present status Idea of future experiment γ-ray spectroscopy of p-shell mirror hypernuclei 12 ΛB Summary

3 CSB effect in s-shell hypernuclear structure Level schema of mirror hypernuclei H / He (before 201) H He p p n n p n + + p n? DB (0 + ) = 0.35 MeV DB (1 + ) = 0.28 MeV B (0 + ):emulsion technique E x (1 + ): γ-ray spectroscopy (NaI) Un expectedly large B Λ difference ( 0.07 MeV in theoretical study with NSC interaction model ) Need to examine old data with modern technique

4 Recent experiment for s-shell Level schema of mirror hypernuclei H / He (before 201) B ( H(0 + )), 2015 (MAMI-A1) MeV (chance to reduce systematic errors) A. Esser, S. Nagao et al., Phys. Rev. Lett. 11, (2015) A1 collaboration., NPA 95 (2016) 19 Precise measurement Emulsion Decay spectroscopy The result supports existence of CSB effect in B Λ(g.s.)

5 Recent experiment for s-shell M. Bedjidian et al., Phys. Lett. B 83, 252 (1979). Level schema of mirror hypernuclei H / He Updated J-PARC E MeV In flight (K-,π-) reaction w/ SKS + Ge detector CSB effect also in excitation energy T. O. Yamamoto et al., Phys. Rev. Lett. 115, (2015)

6 Recent experiment for s-shell Level schema of mirror hypernuclei H / He Updated Existence of CSB effect was confirmed ( B Λ(g.s) and γ-ray ) Strongly spin-dependent : DB (1 + ) = MeV DB (0 + ) = MeV

7 Recent experiment for s-shell Level schema of mirror hypernuclei Need high accurate data H / He Updated to investigate origin of CSB and underlying ΛN interaction Precise γ-ray spectroscopy is powerful tool to study CSB We will continue measurement using Ge detector Existence of CSB effect was confirmed ( B Λ(g.s) and γ-ray ) Strongly spin-dependent : DB (1 + ) = MeV DB (0 + ) = MeV

8 Future measurement Gamma-ray spectroscopy on ΛH (J-PARC E63)

9 Excitation energy [MeV] Gamma-ray data on ΛH Level schema of mirror hypernuclei H / He Three old data are available We obtained high precision data (J-PARC E13) [1] [2] [3] rather large deviation [1] [2] [3] Expected

10 Excitation energy [MeV] Gamma-ray data on ΛH Level schema of mirror hypernuclei H / He Three old data are available We obtained high precision data (J-PARC E13) [1] [2] [3] rather large deviation [1] [2] [3] Expected

11 Limitation on old measurement M. Bedjidian et al. Phys. Lett. B 62, 67 (1976). M. Bedjidian et al. Phys. Lett. B 83, 252 (1979). All γ-ray measurements on ΛH used Stopped K - NaI detector A. Kawachi, Doctoral thesis Univ. of Tokyo (1997) 150 ~ 200 kev(fwhm) resolution due to detector resolution and Doppler broadening For higher precision Stopped K- in-flight (K,π ) NaI detector Ge detector Same strategy as He measurement Expected resolution : ~0 kev(fwhm)

12 Previous study via in-flight 7 Li(K -, GeV/c H (and He) generates as hyperfragment via the in-flight 7 Li(K -, - ) 7 ΛLi reaction BNL AGS Moby Dick 7 Li target 1.1 MeV M.May, PRL 51(1983) MeV Highly unbound γ-ray NaI detector energy resolution : 7 kev(fwhm) + ~80keV Doppler broadening 7 Li They reported ± MeV peak as mixture of H and He Bound region

13 Previous study via in-flight 7 Li(K -, GeV/c H (and He) generates as hyperfragment via the in-flight 7 Li(K -, - ) 7 ΛLi reaction BNL AGS Moby Dick 7 Li target 1.1 MeV M.May, PRL 51(1983) MeV Highly unbound γ-ray NaI detector energy resolution : 7 kev(fwhm) + ~80keV Doppler broadening 7 Li They reported ± MeV peak as mixture of H and He Bound region J-PARC E13 1. MeV

14 Previous study via in-flight 7 Li(K -, GeV/c H (and He) generates as hyperfragment via the in-flight 7 Li(K -, - ) 7 ΛLi reaction BNL AGS Moby Dick 7 Li target 1.1 MeV M.May, PRL 51(1983) MeV Highly unbound 7 Li γ-ray They considered 1.1 MeV peak as H + He mixture + 3 H (now we know this is not the case only H) K - + He + 3 H -> Λ + 3 He + π - [direct] He(K -,π - ) He (0 + only, non-spin-flip) Bound region [two step] Λ + 3 H -> H (Both 0 +,1 +, ratio =1:3 expected) We chose this reaction for H measurement 7 Li

15 γ-ray spectroscopy of H (J-PARC E63) H generates as hyperfragment via the in-flight 7 Li(K -, - ) 7 ΛLi reaction Similar setup as ΛHe measurement SKS spectrometer 7 Li target larger acceptance (~100msr) + good energy resolution beam line spectrometer We can select threshold region of 7 ΛLi* ΛH + 3 He [Ex=~20MeV] (Suppress Doppler broadening) γ-ray ~0 kev (FWHM) Ge detector array (Hyperball-J) Good energy resolution

16 γ-ray spectroscopy of H (J-PARC E63) H generates as hyperfragment via the in-flight 7 Li(K -, - ) 7 ΛLi reaction Similar setup as ΛHe measurement SKS spectrometer 7 Li target beam line spectrometer Ge detector array (Hyperball-J) γ-ray stop Tagging monochromatic π (Support hypernuclear identification) Range counter (additional)

17 Experimental setup for H (J-PARC E63) SKS spectrometer SKS magnet New detector configuration around target (view from beam upstream) Ge detector array Hyperball-J Exp. Target Exp. Target Range counter (additional) Ge Ge Ge Ge Ge Ge Range counter system Thickness: ~0.5 cm thick Layers: >15 layers Coverage: 30 W x 10 H cm Share with other experiment? (weak decay, etc. ) Beam line spectrometer J-PARC K1.1 beamline E x (1 + ) will be measured with <5 kev accuracy (w/6 days beam time)

18 31 participants from 12 institutes J-PARC E63 (E13-2) Submitted in 2015 stage-2 approval H excitation energy 7 Li lifetime (Λ magnetic moment in nuclear medium)

19 Byproduct: γ-ray measurement of 3 H Idea from M. Ukai If nnλ is bound, 3 Λ H (1/2 +, T=1) may be bound Report from GSI Chance to measure γ-rays (iso-spin conversion)

20 Byproduct: γ-ray measurement of 3 H Selecting Ex>20 MeV 1 + ;T=0 0 + ;T=0 He + 1/2 + ;T=1 3/2 + ;T=0 1/2 + ;T=0 H Selecting Ex=~10 MeV 3 He + 3 H Tag 0 MeV pion by range counter H+ 3 He 3/2 ;T=1 a emission 3/2 ;T=0 1/2 + ;T=1 3 H+a 6 Li+ 5 He+d 3/2 + ;T=0 1/2 + ;T=0 7 Li E ex 19.3 ~12 ~ (MeV) Idea from M. Ukai }(K-,π-) p n p substitutional Possible background Chance for high statistic (need for 7 ΛLi lifetime measurement)

21 Preparation status 0.9 GeV/c K - beam for suppress Doppler broadening and higher cross section move to J-PARC K1.1 beam line with SKS magnet J-PARC hadron experimental facility Production target (Au) K1.8BR K1.8 SKS moved to K GeV proton K1.1 KL High-p K1.1 beam line (need construction) Hyperball-J: Established Range counter: Designing (will be constructed in next year)

22 Idea of new measurement Gamma-ray spectroscopy to study CSB effect in p-shell hypernuclei

23 Reaction for γ-ray spectroscopy on mirror hypernuclei Need to extend gamma-ray data to neutron rich side Non-charge exchange reaction 12 C π +, K + 12 Λ C * 12 ΛC + γ Charge exchange reaction 12 C K, π 0 12 ΛB * 12 ΛB + γ π 0 γγ 12 C π, K 0 12 ΛB * 12 ΛB + γ K 0 s π + π - (69%) 12 C e, e K + 12 Λ B * 12 ΛB + γ

24 Reaction for γ-ray spectroscopy on mirror hypernuclei Need to extend gamma-ray data to neutron rich side Non-charge exchange reaction 12 C π +, K + 12 Λ C * 12 ΛC + γ Charge exchange reaction 12 C K, π 0 12 ΛB * 12 ΛB + γ Rather easier! Reaction tag with only charged particles Reasonable beam intensity (for Ge detectors) Prof. Alessandro s talk on Friday π 0 γγ 12 C π, K 0 12 ΛB * 12 ΛB + γ K 0 s π + π - (69%) 12 C e, e K + 12 Λ B * 12 ΛB + γ

25 Setup for the gamma-ray spectroscopy Same setup with ΛH measurement Beam line spectrometer + SKS Hyperball-J SKS spectrometer Beam momentum : 1.05 GeV/c SKS magnet Range counter (similar configuration) SKS magnet Idea from Michelangelo Agnello et al. J-PARC LOI (2016) π + Exp. target π + (high momentum) Ge detector array Hyperball-J Range counter π (low momentum) 12 C π, K 0 12 ΛB * 12 ΛB + γ K 0 s π + π - (69%) Target π beam Beam line spectrometer π - Designing of detector system is ongoing J-PARC K1.1 beamline

26 Summary CSB in s-shell hypernuclear system studied via γ-ray spectroscopy γ-ray spectroscopy on ΛHe (J-PARC E13) E x ( ΛHe(1 + )) = 1.06±0.00 MeV CSB effect also appear in excitation energy + spin-dependence Next step: γ-ray spectroscopy on ΛH (J-PARC E63) In-flight 7 Li(K,π ) reaction + Ge detector Common setup as ΛHe measurement + range counter system Better than 5 kev accuracy w/ 6 days beamtime (stage-2 approval) idea of γ-ray spectroscopy to study CSB in p-shell

27 Backup

28 Toward the exp. completeness for s-shell Gamma-ray spectroscopy of H w/ a few kev accuracy Our Next step J-PARC E63 Gamma-ray spectroscopy of He [J-PARC E13] Done Decay - spectroscopy ( H ) [MAMI-C] Done Counter experiment ( He ) [ J-PARAC HIHR ] Need J-PARC HEF extension

29 Present status of CSB in s-shell Existence of CSB effect was confirmed ( B Λ(g.s) and γ-ray ) Difference in 0 + and 1 + : DB (1 + ) = MeV DB (0 + ) = MeV Strongly spin-dependent CSB effect calc. w/ ΛΣ mixing Exp. (old) Exp. (new) Calc. Nogga Calc. Gal (unit : MeV) Calc. Gazda DB (1 + ) 0.28(5) 0.03(5) DB (0 + ) 0.35(5) 0.35(5) A. Nogga et al., Phys. Rev. Lett. 88, (2002). A. Gal, Phys. Lett. B 7, 352 (2015). D. Gazda, A. Gal, NPA 95 (2016) 161 Widely accepted NSC97e interaction model simple potential Chiral EFT model N- N coupling may be key of CSB effect High accurate data of CSB effect may provide new information to investigate underlying ΛN interaction

30 Yield estimation of H BNL exp E63 Total K- 10 G Kaon 5 G Kaon Target thickness 8 g/cm 2 15 g/cm 2 spectrometer Moby-dick (18 msr) SKS (35 msr < 6 ) g yield g-ray Efficiency 6% 3% (x 0.8 live) H(1 + ) yield 12,500 H(0 + ) yield Direct + g-feeding 16,200

31 Decay counter configuration for lifetime measurement PhysRevC.3.89 Range counter system for hypernuclear - decay in BNL (B) Timing scintillator (A) MWPC (C) Range counter Plastic scintillator Total 7.6cm thickness (c) 5 He + other (a) 3 H 3 He+ (b) H He+ (D) Veto counter Range counter Total E resolution ~ MeV (d) 6 Li+ p + (in-flight) Optimum missing mass gate of 7 Li Certain states will be enhanced. Lifetimes of 3 H, H can be measured

32 CSB data in p-shell hypernuclei Theoretical study: 10~100 kev CSB effect in p-shell A. Gal, Phys. Lett. B 7, 352 (2015). Existing data on B Λ Experiment with (e,e K + ) reaction (JLAB) -> A=7, 10 hypernuclei (~100 kev accuracy) T. Gogami et al.: Phys. Rev. C 9 (2016) T. Gogami et al.: Phys. Rev. C 93 (2016) Difficulty: Need accurate data in both mirror pair

33 Hyperball-J new Ge detector array Features Large photo-peak efficiency ε ~6 MeV with 32 Ge detectors Fast readout system Low temp. Ge detector for radiation hardness Mechanical cooling Fast background suppressor PWO counter for high intensity hadron beam Lower half of Hyperball-J Ge detector PWO counter Target Developed Ge detector Pulse-tube cooler