Ponente
Descripción
A.Gadea, A.Algora, A.I.Morales, J.J. Valiente Dobon R.M. Perez Vidal, R.Illicachi, et al.
IFIC, CSIC-University of Valencia, Spain
A.Gottardo, G.de Angelis,et al.
INFN Laboratori Nazionali di Legnaro, Legnaro, Italy
A. Jungclaus, P. Sarriguren, et al.
Instituto de Estructura de la Materia, IEM-CSIC, Madrid, Spain
P.Doornenbal, et al.
RIBF, RIKEN, Japan
M.Górska, et al.
GSI-Darmstadt, Germany
and the Ge array, WAS3ABI, RIBF, and BigRIPS Collaborations
This proposal aims to study the Gamow-Teller (GT) $\beta$-decay of the the Tz=-1 $^{78}Zr$ and $^{82}Mo$ nuclei, determining lifetime, excitation energies and B(GT) rates to the low lying $1^+$ states in $^{78}Y$ and $^{82}Nb$ respectively. The energy differences of the T=0 and T=1 ground states in this self-conjugate (N=Z) nuclei as well as the presence of T=0 proton-neutron (p-n) pairing condensate, will be investigated through the GT -decay strength of the Tz=-1 Jπ=0+ T=1 ground state into the Jπ=1+ T=0 in the odd-odd N=Z nucleus. The SU(4) symmetry, responsible of the super-allowed GT decays in light systems, is strongly suppressed in heavy ones due to the spin-orbit splitting. Proton-neutron pairs represent a generalization of the SU(4) symmetry, therefore, low-lying T=0 collective modes in odd-odd N=Z nuclei can elicit a super-allowed GT decay. Previous attempts to investigate this phenomenon in the decay of $^{62}Ge$ [1] and $^{70}Kr$ [2] have been inconclusive. Recent studies indicate that T=0 p-n pairing will be more relevant in N=Z nuclei with Z>~40 where p-n pairs are predicted to create a T=0 condensate [3]. In fact, finding of delay alignments on the level schemes of $^{84}Mo$ [4] and $^{88}Ru$ [5] have been suggested to originate by the onset of the T=0 pn pairing.
The $^{82}Mo$ nucleus is possibly the heaviest Tz=-1 for which such investigation is feasible at RIBF with BigRIPS. The parent nuclei $^{82}Mo$ and $^{78}Zr$ parent nuclei will be populated in the fragmentation of a 140 pnA intensity $^{124}Xe$ beam at 345 MeV·A, in a 740 mg/cm2 Be target, with a cross section of 0.6pbarn and 6pbarn respectively.
The separated fragmentation products will be implanted in the WAS3ABI Si array. The $^{78}Y$ and $^{82}Nb$ $\beta$-delayed $\gamma$-rays will be studied with the HPGe array.
[1] E. Grodner et al. Physical Review Letters 113 (2014): 092501.
[2] A. Vitéz-Sveiczer et al. Physics Letters B 830 (2022): 137123.
[3] J. Jänecke, et al. Phys. Lett. B 605 (2005) 87.
[4] N. Mărginean et al. Physical Review C 65.5 (2002): 051303.
[5] B.Cederwall et al. Physical review letters 124.6 (2020): 062501.
