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J-PARC での 中性子過剰ラムダ ハイパー核生成実験 Production of Neutron-Rich L Hypernuclei at J-PARC

J-PARC での 中性子過剰ラムダ ハイパー核生成実験 Production of Neutron-Rich L Hypernuclei at J-PARC. 大阪大学理学研究科 阪口 篤志 Atsushi Sakaguchi (Dep. of Physics, Osaka Univ.). CR. Studies of L Hypernuclei. Hypernuclei ( L hypernuclei) Bound state of hyperon ( L ) and nuclei How to study?

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J-PARC での 中性子過剰ラムダ ハイパー核生成実験 Production of Neutron-Rich L Hypernuclei at J-PARC

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  1. J-PARC での中性子過剰ラムダハイパー核生成実験Production ofNeutron-Rich L HypernucleiatJ-PARC 大阪大学理学研究科 阪口 篤志 Atsushi Sakaguchi (Dep. of Physics, Osaka Univ.) 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012

  2. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 CR Studies of L Hypernuclei • Hypernuclei (L hypernuclei) • Bound state of hyperon (L) and nuclei • How to study? • Emulsion and bubble chambers • Discovery by Danysz and Pniewski in CR • K- beams at CERN • LL: KEK-PS, (BNL-AGS), J-PARC, … • Missing-mass spectroscopy • CERN-PS • BNL-AGS • KEK-PS • DAFNE • JLAB, MAMI-C, … • J-PARC, … Hypernucleus weak decay • feasibility

  3. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Missing-Mass Spectroscopy at CERN • Heidelberg-Saclay-Strasbourg Collaboration SPES II

  4. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Studies of L Hypernuclei (2) • How to study? • g-ray spectroscopy • CERN-PS (4LH, 4LHe) • BNL-AGS, KEK-PS • J-PARC, … • Invariant-mass spectroscopy in HI collisions • BNL-AGS • BNL-RHIC (discovery of anti-hypernuclei) • GSI-SIS, FAIR, … • Weak decay of L hypernuclei • Achievement in experiments? • Production of identified hypernuclei • Better and better energy resolution with missing-mass cut can achieve good S/N proton-rich L hypernuclei, …

  5. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Properties of L Hypernuclei • Single particle picture is OK • Beautiful L shell structure • Deeply bound L state • Highly excited L bound state • “Glue-like role” of L hyperon • L-N interaction is attractive • Possible to stabilize nuclei • Doorway to strange matter • Spin dependent interaction • Weak spin-orbit force • What else? • LN-SN mixing, … n n p n n glue-like role p n n L n n

  6. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Large area un-explored ! “glue” like role of L hyperon Nuclear Chart with Strangeness Expand hypernuclear chart by using new spectroscopic tools

  7. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Production Reactions • Emulsion experiment • K- beams stopped in target • Produce “hyperfragment” • Information of BE of g.s. • precise energy determination • but low statistics • Missing-mass spectroscopy • “identified” hypernuclei • K- or p- beams • Obtain level structure • high statistics • Mainly Non Charge-eXchange (NCX) • available targets restricted NCX

  8. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Production Reactions • Missing-mass spectroscopy 2 • Charge exchange reactions • Single CX reactions (SCX) • (e,e’K+) • thin target available • (K-,p0), (p-,KS) • new spectrometer • Double CX reactions (DCX) • (p-,K+), (K-,p+) • access neutron-rich hypernuclei • L. Majling NP A585 (1995) 211c • possible with existing setup • very low cross section ! • roughly 1/1000 of NCX SCX DCX J-PARC E10

  9. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 p 1H Stable 2H Stable 3H Stable 4H No evidence 5H Resonance 6H No evidence n glue like role of L L 2LH Not bound 3LH Stable 4LH Stable Production Exotic n-rich L-hypernuclei • Example of “Hydrogen” Super Heavy Hydrogen 5LH No evidence 6LH Stable ? 7LH Stable ? We can produce at J-PARC Hyper Heavy Hydrogen

  10. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Super Heavy Hydrogen • Resonance state in 5H system • at Dubna • p(6He,ppt)nn (tnn=5H) PRL 87 (2001) 092501 • 3H(t,p)5H PL B566 (2003) 70 • 2H(6He,3He)5H NP A719 (2003) 229c • Missing mass spectra (Ex of 5H(t+n+n system)) p(6He,pp)X

  11. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Super Heavy Hydrogen (2) • at GSI • p(6He,2He)5H NP A723 (2003) 13 • at LAMPF • 9Be(p-,pt)5H EPJ A24 (2005) 231 • 9Be(p-,dd)5H • 6LH structure 5H structure • Some feedback to structure of normal nuclei

  12. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 if core isospin=0 A(I=0) A(I=0) L S Energetically Suppressed A*(I=1) mass diff. ~1/4  larger mixing if core isospin0 S A(I0) A(I0) L OK! S LN-SN Mixing in L Hypernuclei • B.F. Gibson et al. PR C6 (1998) 433c ordinary nuclei hypernuclei XN 25MeV LL DN SN 77MeV 290MeV LN NN S=0 S= -1 S= -2 important in neutron-rich L-hypernuclei (large isospin)

  13. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Coherent LN-SN Coupling • Over/under-bound problem • Hard to understand BE of light hypernuclei • adjust A=4 hypernuclei  5LHe over-bound • adjust 5LHe  A=4 hypernuclei under-bound Y. Akaishi PTPS 186 (2010) 378

  14. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Coherent LN-SN Coupling (2) • Coherent LN-SN coupling • Additional attraction for 4LH and 4LHe (I=1/2) • Y. Akaishi et al. PRL 84 (2000) 3539 • a kind of LNN 3-body force • Strongly state dependent? • important to understand structure of L hypernuclei

  15. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Mixing in Neutron-rich Hypernuclei • LN-SN mixing effect important Coherent LN-SN mixing originally introduced to explain A=3-5 hypernuclei Normal LN interaction BL ~ 4.4 MeV Coherent LN-SN mixing effect BL ~ 4.4+ 1.4MeV Precise measurement of B.E.  Estimation of mixing effect Y. Akaishi et al. Frascati Phys. Ser. XVI (1999) 59

  16. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 L-matter Interaction (MeV) Mixing and EoS in Neutron Stars • Hyperon content in core of neutron stars • Degree of LN-S0N mixing and EoS no mixing Hard EoS p-fraction with mixing p-fraction Soft EoS large mixing S. Shinmura et al. J.Phys G28 (2002) L1

  17. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Mixing and EoS in Neutron Stars (2) • Strangeness degree of freedom inevitable • What kinds of strangeness appear ? • Controlled by mass, charge and interaction. large n/p asymmetry(isospin»1) strong LN-SN mixing expected study on neutron-rich hypernuclei may provide information S. Balberg and A. Gal NP A625 (1997) 435

  18. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Bound or Unbound ? • QF production and n-decay thresholds • Systematics of BEL of known light hypernuclei -4.6MeV from systematics L QF threshold n bound threshold mass number of core nuclei

  19. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Bound or Unbound ? (2) • Expected 9LHe spectrum • “core” nucleus is 8He (well known halo nuclei) • What kind of configuration is dominant in g.s.? L QF threshold -8.3MeV from systematics n bound threshold ~3MeV

  20. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 9LHe 6LH Bound or Unbound ? (3) • Deviation from systematics • Contribution of LN residual interaction • Spin-dependent int., LN-SN coupling, … • Effect is small: Need precise measurements 9LBe 10LLi （E521） 4LHe 4LH

  21. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Studies of Neutron-rich Hypernuclei • KEK-PS (SKY) • K. Kubota et al. NP A602 (1996) 327 • (stopped K-,p+) reaction • Production upper limit 9LHe: < 2.4x10-4 /(stopped K-) 12LBe: < 6.1x10-5 /(stopped K-) 16LC: < 6.2x10-5 /(stopped K-) 12LC g.s.: 9.8±1.2 x10-4 /(stopped K-) H. Tamura et al. PTPS 117 (1994) 1

  22. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Studies of Neutron-rich Hypernuclei (2) • DAFNE (FINUDA) • M. Agnello et al. PL B640 (2006) 145 • (stopped K-,p+) reaction • (K- abs.)-p+ vertex cut • reject in-flight S+ decay • Production upper limit p+ p+ p- p- production S+ decay K- K- Acceptance Cut? Signal Background 6LLi: < 2.5x10-5 /(stopped K-) 7LLi: < 4.5x10-5 /(stopped K-)

  23. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Studies of neutron-rich Hypernuclei (3) • DAFNE (FINUDA) • M. Agnello et al. PRL 108 (2012) 042501 • 6Li(stopped K-,p+) reaction • measure also weak decay • cut on T(p+)+T(p-) • 3 events of candidates 2.9±2.0x10-6 /(stopped K-) Dalitz Akaishi

  24. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 K6 beam line @KEK-PS SKS spectrometer good energy resolution DBL = 2.5MeV (FWHM) 47 events in bound region ds/dW~10nb/sr (1/1000 of NCX) DCX (p-,K+) Reaction • KEK-PS (E521) • S. Pranab et al. PRL 94 (2005) 052501 • reaction • Clean reaction g.s. BL=0

  25. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 DCX (p-,K+) Reaction (2) • KEK-E521 data • Beam momenta: 1.05GeV/c and 1.2GeV/c • ds/dW(1.05GeV/c) < ds/dW(1.2GeV/c) pbeam = 1.05 GeV/c pbeam = 1.2 GeV/c

  26. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Reaction Mechanism • Optimum p beam momentum ~ 1.2GeV/c • E521 experiment tells • Puzzle of reaction mechanism of DCX • Naïve two-step reaction

  27. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Reaction Mechanism (2) • Tendency of elementary process

  28. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Reaction Mechanism (3) • Possibility of other mechanisms • One-step reaction with LN-SN mixing • Elementary cross section LN-SN mixing S channel opens at 1.045GeV/c

  29. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 One Step DCX Mechanism • LN-SNcoupled channel calculationfor the DCX reaction by Harada et al. • Spectrum is sensitive to mixing interaction VLSand S-N interaction WS • Bound region→VLS • Continuum region→WS WS VLS More yield is necessary to make detailed discussions

  30. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Measurement over Wide Mass Range • One step mechanism and mass spectra • If one step mechanism is dominant: • L(QF)/S-(QF) ratio, shape of L(QF), … • Measurement and understanding of full spectrum are quite important (p-,K+) S region interference? L region Missing Mass LN-SN Mixing

  31. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Which is better (p-,K+) or (K-,p+) ? • Cross-section-wise, these are competitive. • (K-,p+) data exist • Dibaryon search • p+ from KS decay • Tough measurement • Need KS rejection (1) if beam duty factor is good (2) @K1.1, 270kW beam power (30GeV,9mA) (3) @K1.1, 270kW beam power Czech. J. Phys. 42 (1992) 1089

  32. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 J-PARC E10 Proposal • Subject • Production of neutron-rich hypernuclei • higher statistics than previous experiments • Hypernuclei close to neutron drip-line • 6LH: core is 5H resonance, beyond neutron drip-line • 9LHe: core is 8He, typical neutron halo nucleus • Effect of LN-SN mixing in n-rich hypernuclei • precise measurement of binding energies • Reaction mechanism • two step or one step? • optimum beam momentum? • Method • Missing-mass spectroscopy by (p-,K+) reaction • method has been established at KEK-PS E521

  33. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Experimental Setup • K1.8 beam line • 1.2 GeV/c p- beams • Good momentum resolution: Dp/p~10-4 • 5kW beam is enough to obtain 107p/spill SKS ESS2 D4 D4 D3 ESS1 K1.8 beam line 30GeV p D1,D2

  34. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Experimental Setup (2) • SKS spectrometer • Good momentum resolution: Dp/p~10-3 • Large acceptance:W~100msr January 2010 before earthquake by K. Tanaka

  35. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Experimental Setup (3) • SKS spectrometer • Moved from KEK-PS K6 to J-PARC K1.8 • momentum acceptance enlarged: good for E10 SKS @KEK-PS K6 SKS @J-PARC K1.8 SDC3, 4 from BNL D-line TOF Old+New Large AC New LC Old+New

  36. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Experimental Setup (4) • SKS spectrometer • Simultaneous L and Smeasurement • monitoring of stability also possible Hypernuclei production S- production

  37. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Yield estimation for 6LH production • Cross section ~10nb/sr (~1/1000 of NCX) • Major difficulty in this experiment • About 300 events in 3 weeks of beamtime • 6 times larger KEK-E521 (47 events) • Discussion on level structure possible with new data High intensity beams Large acceptance

  38. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Prospects on B.E. measurement • Measurement of B.E. of 6LH • Assumptions • overall energy resolution • 6LH yield • 6LH/QF ratio (Ex<23MeV) simulated spectrum 6LH estimated from 4LHe and 10LLi Well separated from QF Statistical error of B.E. < 0.1MeV Minimize systematic errors L bound

  39. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Prospects on B.E. measurement (2) • Energy resolution affects S/N • good energy resolution is essential • Study of energy resolution in progress • 1H(p-,K+)S-runs in February 2012 (E19-2) • 12C(p+,K+)12LC run in June 2012 (E27)

  40. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Calibration of Absolute Missing-Mass • No established calibration peak in (p-,K+) • Calibration in 3 or 4 steps • Calibration with 12LC (beam: p+, SKS: K+) • calibration in mass range of hypernuclei • Is 12LC good for calibration? (claim by Fukuda) • Calibration with S+ (beam: p+, SKS: K+) • Calibration with S-(beam: p-, SKS: K+) • correct mass and/or estimate systematic error due to beam polarization change • 80MeV/c2 away from mass range of hypernuclei • Monitoring with S-(beam: p-, SKS: K+) • test of stability of missing-mass in production runs

  41. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Run Plan: E10 1st Step • 2012 June (E27 production run) • for preparation of E10 • trigger rate study (@1.2GeV/c, DCX) • energy resolution study (12LC, S-) • tracking detector study (fiber tracker, etc.) • Consideration before production run • Energy resolution good enough? • How high beam intensity we can handle? • Optimum target thickness? • 2012 Autumn (E10 production run) • Beam intensity at least 3x106p-/spill • 5x106p-/spill might be possible • Production of 6LH (at least 100 events)

  42. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Near Future Plan: E10 2nd Step • Subjects • More statistics for 6LH • beams with better duty factor • new tracking detectors (fiber, GEM, SSD, …) • Production of 9LHe • At where and how? • We need beam momentum around 1.2 GeV/c • K1.8 beam line is only candidate at present • If extended K1.1 beam line accepts beam momentum close to 1.2 GeV/c, it is also a candidate • We need spectrometer with good momentum resolution • S-2S at K1.8? Resolution better than SKS? • SKS at extended K1.1?

  43. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Future Plan • Dilemma of experiments with pion beams • Primary beam intensity does not limit p- beam intensity even at 5kW beam power • We can’t handle very high intensity p- beams • Beam power increases year by year • Improvement of slow-extraction technique SX power upgrade plan (mod-term)

  44. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Future Plan (2) • Need new spectrometer to use full beams • HIHR and Hi-PiBF proposed by H.Noumi • Quite suitable for DCX reactions • Beam line and spectrometer with dispersion matching technique • Established technique at lower energy • EPICS@LAMPF, Grand-RAIDEN@RCNP • Avoid to measure beam to achieve 109p-/spill or higher beam intensity • Measure only scattered K+ • Dispersion matching technique improves also momentum resolution: 1.5 MeV →a few 100 keV

  45. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 HIHR Beam Line and Spectrometer • Handle high intensity and high resolution • Beam line • Vertical dispersion on target • Spectrometer • Tracking only at exit • Horizontal position •  mom. of scattered particle • Vertical position •  beam momentum H. Noumi , J-PARC LOI-08

  46. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 HIHR Beam Line in Hadron Hall

  47. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Hi-PiBF in Extended Hadron Hall • High Intensity Pion Beam Facility (Hi-PiBF) • H.Noumi, HUA WS, 23 October 2011 Challenging !

  48. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Hi-PiBF in Extended Hadron Hall (2) • K.Tanaka, HUA WS, 23 October 2011

  49. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Summary • We wish to expand hypernuclear chart • “glue-like role” of L hyperon • possibility of production of n-rich hypernuclei • LN-SN coupling effect is more important • hypernuclei close to neutron drip-line • close relation with normal neutron-rich nuclei • DCX reaction is promising • new tool of missing-mass spectroscopy • the (p-,K+) reaction has been established • also reaction mechanism may provide a hit of LN-SN coupling

  50. 第２２回原子核ハドロン物理セミナー@JAEA, 15 March 2012 Summary (2) • J-PARC E10 experiment • new neutron-rich hypernuclei: 6LH, 9LHe • 6 times higher statistics than KEK-E521 • precise measurement of binding energy of neutron-rich hypernuclei • measurement of wide mass range at a time • preparation in progress at J-PARC K1.8 beam line → production run in 2012 Autumn • Future • higher statistics with better beam duty factor • HIHR or Hi-PiBF is ideal beam line for measurement of the DCX reaction

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