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

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

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 pL states 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)

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

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

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

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

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

Spectra of a deformed even-even nucleus (collective excitation mode) g-band 22+ 31+ 42+ E(41+)/E(21+) b-band 02+ 23+ 43+ 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

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

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

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

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

Use of a natural Mg target sL pL dL 24Mg (0+) 0.79 L 24LMg 23LNa 23LMg core 23Mg 22Na 22Mg 25Mg (5/2+) 0.10 25LMg 24LMg 24 26Mg 0.11 26LMg 25LNa 24Na even-even odd-A odd-odd

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

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

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 of the inter 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