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Production of Neutron-Rich L-Hypernuclei with Charge-Exchange Reaction<br>

Explore the production of exotic L-hypernuclei close to neutron drip-line, studying LN-SN mixing effects and connections to EoS in neutron stars. <br>

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Production of Neutron-Rich L-Hypernuclei with Charge-Exchange Reaction<br>

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  1. P10-1: Production of Neutron-Rich L-Hypernuclei with the Double Charge-Exchange Reaction(update of P10: Study on L-Hypernuclei with the Charge-Exchange Reactions) Collaboration: Osaka Univ., KEK, Osaka E. Univ., Seoul Natl. Univ., JAEA, Univ. Torino, INFN and INAF-IFSI Co-Spokespersons: Atsushi Sakaguchi (Osaka Univ.) Tomokazu Fukuda (Osaka E.-C. Univ.) Ajimura P10-2: on weak decay of L-hypernuclei

  2. Subjects of proposal P10-1 • Production of neutron-rich L-hypernuclei • L-hypernuclei close to neutron drip-line • Quite exotic objects if mass number is small • L-nucleus interaction in high isospin state • Structures of hypernuclei  L-N interaction in neutron-rich environment • LN-SN mixing is important if isospin0 • Close connection to EoS in neutron stars at J-PARC PAC Meeting, 11 January 2007

  3. Large area un-explored ! “glue” like role of L hyperon Nuclear chart with strangeness at J-PARC PAC Meeting, 11 January 2007

  4. isospin=3/2 or 2 KEK-E521 Single CX Double CX this proposal Expand the hypernuclear chart L-hypernuclei isospin=0 or 1/2 Non Charge-Exchange ordinary nuclei hyperfragments by emulsions exp. at J-PARC PAC Meeting, 11 January 2007

  5. 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 Exotic L-hypernuclei • Example of “hydrogen” Super Heavy Hydrogen 5LH No evidence 6LH Stable ? 7LH Stable ? We can produce at J-PARC Hyper Heavy Hydrogen at J-PARC PAC Meeting, 11 January 2007

  6. if isospin=0 A(I=0) A(I=0) L S Energetically Suppressed A*(I=1) mass diff. ~1/4  larger mixing if isospin0 S A(I0) A(I0) L OK! S LN-SN mixing effect ordinary nuclei L-hypernuclei DN SN 77MeV 290MeV LN NN S=0 S= -1 important in neutron-rich L-hypernuclei (large isospin) at J-PARC PAC Meeting, 11 January 2007

  7. EoS of matter in neutron star • 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 at J-PARC PAC Meeting, 11 January 2007

  8. K6 beamline @KEK-PS SKS spectrometer good energy resolution DBL = 2.5MeV (FWHM) ~45 events in bound region ds/dW~10nb/sr (1/1000 of NCX) How to produce n-rich L-hypernuclei • KEK-E521 experiment established • reaction • Clean reaction g.s. BL=0 Increase yield 10 at J-PARC at J-PARC PAC Meeting, 11 January 2007

  9. Experimental setup at J-PARC Excellent resolution Large acceptance • K1.8 beamline + SKS ready at very early stage of Day-1 High intensity p beam (1.2GeV/c) beam intensity ~10M p-/spill not limited by primary beam at J-PARC PAC Meeting, 11 January 2007

  10. High beam intensity Large acceptance Yield: 9LHe production • Particle bound clear observation of g.s. • ds/dW=10nb/sr is assumed (same order as 10LLi hypernucleus) • 310 events in 3 weeks • 7 times larger KEK-E521 • Discussion on level structure possible if beam spill longer (3sec)  2 at J-PARC PAC Meeting, 11 January 2007

  11. Yield: 6LH production • Simple estimation tells binding is marginal • May be bound or maynot • May observe even unbound g.s. if width is narrow • Yield estimation has large ambiguity • Exotic nature of 6LH: overlap of w.f. smaller ? • Production cross section may be smaller ? • Yield vs. information • ~50 events: discuss “bound” or “not bound” • ~300 events: some discussion on level structure Pessimistic estimation Optimistic estimation at J-PARC PAC Meeting, 11 January 2007

  12. Time schedule FY06 FY07 FY2008 FY09 • Need only K1.8 beamline and SKS • Beamline and detectors will be ready in FY08 • Collaboration with E05 beamline spectrometer SKS spectrometer at J-PARC PAC Meeting, 11 January 2007

  13. Summary of proposal • Double CX: New spectroscopic tool • Hypernuclei close to neutron drip-line: 9LHe • Exotic L-hypernuclei: 6LH • Expect higher statistics than KEK-E521 • Information from neutron-rich L-Hypernuclei • L-N interactionin neutron-rich environment • LN-SN mixing effects • Small L-S mass difference • Important if core nucleus has non-zero isospin • Close connection to the EoS of matter in neutron stars (isospin»1) at J-PARC PAC Meeting, 11 January 2007

  14. at J-PARC PAC Meeting, 11 January 2007

  15. Backup Slides

  16. Flavor SU(3) symmetry • u and d quarks SUF(2) •  u, d and s quarks SUF(3) • proton and neutron • and hyperons • Lightest hyperon (L) • L-hypernuclei • Another stable “nuclei” • Other hyperons • LN-SN mixing occur • Affect to L-nucleus interaction S=0 n p S= -1 S- L S0 S+ S= -2 X- X0 at J-PARC PAC Meeting, 11 January 2007

  17. N p, r, w, h, ... N Y p, K, r, w, K*, ... N S= +1 K0 K+ • NN and YN int. • SUF(2)SUF(3) p- p0 h p+ S=0 Ordinary nuclear force K- S= -1 K*0 K*+ S= +1 Extension to YN interaction r- r0 w r+ S=0 K*- S= -1 at J-PARC PAC Meeting, 11 January 2007

  18. if core isospin=0 SL XN A(I=0) A(I=0) 26MeV L S LL N N Energetically Suppressed A*(I=1) N S mass diff. ~1/4  larger mixing if core isospin0 A(I0) A(I0) N L OK! S S= -2 LN-SN mixing effect D S 77MeV 290MeV L N S=0 S= -1 Important in n-rich (or p-rich) L-hypernuclei at J-PARC PAC Meeting, 11 January 2007

  19. Structure of 9LHe hypernucleus • Expected to be particle stable • Core nucleus 8He is particle bound • Practical decay thresholds • Naive extrapolation of BL tells BL~8MeV •  3 MeV more bound than 8LHe+n threshold ～ 8.2MeV ～ 3MeV at J-PARC PAC Meeting, 11 January 2007

  20. Structure of 6LH hypernucleus • Unbound 5H • 1.7 MeV unbound • Exist as resonance • “Superheavy Hydrogen” • Bound 6LH ? • glue-like role of L • BL= 0.5~2 MeV ? • “Hyperheavy Hydrogen” at J-PARC PAC Meeting, 11 January 2007

  21. repulsive SN-int. Ingredients of neutron stars • Core of neutron stars • Need strangeness degree of freedom • What kinds of strangeness appear ? • Controlled by mass, charge, interaction, etc. at J-PARC PAC Meeting, 11 January 2007

  22. LN-SN mixing in neutron star • Large n/p asymmetry (isospin»1) • LN-SN mixing is quite natural • Information on mixing for EoS discussion • Study ofneutron-rich hypernuclei may provide at J-PARC PAC Meeting, 11 January 2007

  23. Ordinary n/p/e/m matter Hyperon matter M / MS central density (g/cm3) EoS and mass of neutron stars • Upper bound of neutron star mass <1.5MS at J-PARC PAC Meeting, 11 January 2007

  24. L-matter Interaction (MeV) LN-SN mixing effect on EoS • Degree of LN-S0N mixing and EoS no mixing Hard EoS p-fraction p-fraction with mixing Soft EoS large mixing at J-PARC PAC Meeting, 11 January 2007

  25. Single step Two step 1.05 1.2 Results of KEK-PS-E521 experiment 1.2 GeV/c • Cross section • pp=1.2 GeV/c • pp=1.05 GeV/c • Reaction mechanism 1.05 GeV/c at J-PARC PAC Meeting, 11 January 2007

  26. SKS energy resolution • Summary of experimental resolution 2.5 MeV (FWHM) 3.5 g/cm2 at J-PARC PAC Meeting, 11 January 2007

  27. Calibration • BL and Ex calibration • 12LC production by the (p+,K+) reaction • Ground state (s1/2,L): BL=10.760.19 MeV • Excited state (p3/2,L): Ex=11.00  0.03 MeV • Obtain response function (peak shape) • No change in SKS, beamline polarity change • Symmetry of p+/p- beams • Narrow acceptance of beamline • 1 shift for every 1 week • DBL, DEx ~ 0.05 MeV (stat.) at J-PARC PAC Meeting, 11 January 2007

  28. Length of Flat Top vs Yield • 10MHz beam operation assumed ~ 2 yield assumed in yield estimation at J-PARC PAC Meeting, 11 January 2007

  29. Time schedule of “weak decay” experiment FY06 FY07 FY08 FY09 at J-PARC PAC Meeting, 11 January 2007

  30. High Intensity and High Resolution beamline • handle 109p/spill • Dp/p ~ 10-4 at J-PARC PAC Meeting, 11 January 2007

  31. High Intensity and High Resolution beamline(new configuration) at J-PARC PAC Meeting, 11 January 2007

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