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g -ray spectroscopy of the sd -shell hypernuclei

g -ray spectroscopy of the sd -shell hypernuclei. Graduate school of Science, Tohoku University T. Koike Hyperball-J collaboration. Survey of sd-shell hypernuclear cores g -ray spectroscopy of well deformed hypernuclei 25 L Mg Summary. E13. Z=20.

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g -ray spectroscopy of the sd -shell hypernuclei

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  1. g-ray spectroscopy of the sd-shell hypernuclei Graduate school of Science, Tohoku University T. Koike Hyperball-J collaboration • Survey of sd-shell hypernuclear cores • g-ray spectroscopy of well deformed hypernuclei • 25LMg • Summary

  2. E13 Z=20 Possible sd-shell L hypernuclei via g-ray spectroscopy with (K-,p-) & (p+,K+) reactions 39Ca 40Ca 38K 39K 38Ar 39Ar 40Ar 37Cl 34Cl 35Cl 36Cl 39Cl 31S 34S 36S 32S Z 30P 31P 28Si 30Si 27Si 26Al 27Al Most abundant isotopes (target) 26Mg 23Mg 24Mg 25Mg ~10% abundance 23Na 24Na 25Na 22Na proton decay 20Ne 22Ne 19Ne 21Ne neutron decay 18F 19F 21F N Z=9

  3. Bound states of sd-shell nuclei and hypernuclei • Co-existence of shell (mean field) and cluster-like structures • More valence nucleons • higher level densities (especially odd-odd) • Collective (rotational) excitation spectrum → low-lying energy • pLstates also bound • Shell model • Cluster model • Self-consistent calculations (12/4 Hagino) • RMF • Hatree-Fcok+BCS • AMD (12/4 Kimura) D. J. Millener et al., Phys. Rev. C, 38 2700 (1988)

  4. Bn Bp Ex(pL) Target A -1ZXn-1

  5. 28LSi dL pL sL A-1LZ-1 g SKSMinus? A-1LZ g-g coincidence with Hyperball-J (p+,K+) T.Hasegawa et al., Phys. Rev. C 53, 1210 (1996) g g ALZ Weak decay (mostly via non-mesonic in the sd-shell hypernuclei)

  6. even-even mirror E13 Z=20 Possible sd-shell L hypernuclei via g-ray spectroscopy with (K-,p-) & (p+,K+) reactions 39Ca 40Ca 38K 39K 38Ar 39Ar 40Ar 37Cl 34Cl 35Cl 36Cl 39Cl 31S 34S 36S 32S Z 30P 31P 28Si 30Si 27Si 26Al 27Al Most abundant isotopes (target) 26Mg 23Mg 24Mg 25Mg ~10% abundance 23Na 24Na 25Na 22Na proton decay 20Ne 22Ne 19Ne 21Ne neutron decay 18F 19F 21F N Z=9

  7. Non collective oblate (b, g=60°) triaxial g spherical b Collective prolate (0,0) (b, g=0°)

  8. Skyrme Hartree-Fock +BCS Myaing Thi Win et al., submitted to PRC • self-consistent mean field • Skyrme-type LN interaction • PES of L hypernuclei with triaxial deformation: E(b,g) • Angular momentum not good quantum number 24Mg, 24Mg+L +L

  9. 42+ E(41+)/E(21+) 31+ 43+ 22+ 23+ g-band 02+ b-band Spectra of a deformed even-even nucleus (collective excitation mode) 41+ g 21+ vibrational v.s. rotational 0+ K=0, nb=1, ng=0 b2, J K=2, nb=0, ng=1 K=0, nb=0, ng=0

  10. 18(▲) ,20Ne 22(▲) ,24Mg 30S 38Ar 38Ca 26Si 21+, 22+, and 02+

  11. Rotational 24Mg 38Ca 20Ne 26Si 38Ar 22Mg Vibrational 18Ne Rotational v.s. Vibrational

  12. g-ray spectroscopy of 25LMg • Well deformed & even-even core hypernuclei • low and simple (regular) energy level • direct observation of core polarization effect of L • Nuclear density saturation at the g.s. with little change in size, but a shape can change in (b,g) plane • A few 100 keV change • Observation of spin averaged 21+, 22+, 02+→（b,g） • Observation of 41+ • pL-bound-states particle stable (Bp=11693keV Bn=16532 keV) • Observation of pL splitting in the sd-shell • Hyperball-J with LaBr, CsI detectors (?) • Use of a natural target • possibility of increasing the number of accessible hypernuclei • a test case for heavier hypernucley beyond sd-shell

  13. 24Mg level scheme pL pL pL T=0 T=0 12C 13LC 24Mg 25LMg

  14. Use of a natural Mg target even-even odd-A odd-odd

  15. Mg even-even core: 22,24Mg T=0 T=0 2212Mg10(2) 2412Mg12(4)

  16. 26LMg 25LMg 24LMg 23LMg 11% 10% 79% 23LNa 24LNa Use of natural Mg target and identification of six L hypernuclei (1) Natural Mg (2) 27Al (3) 23Na sL, dL sL ,pL sL dL 27Al(K-,p-) → p+26LMg (pL gate) ←dL 23Na(K-,p-)→23LNa (sL gate)

  17. Summary • The sd-shell region more vast than the p-shell • Importance of coupling of L to nuclear collectivity (non-spherical vacuum) in the sd-shell • Core polarization effect of L in the 2D (b,g) plane • Measurement oftheinter shell (pL→sL) g ray • g-ray spectroscopy of 25LMg with a use of natural target (Hyperball-J, SKSMinus, LaBr3/CsI detectors?) • Essential role of g-g coincidence technique in the sd-shell

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