Neutron-proton correlations in an exactly solvable model
- Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina 27599 (United States)
- Bartol Research Institute, University of Delaware, Newark, Deleware 19716 (United States)
- Institute of Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, Sofia-1784 (Bulgaria)
- Department of Physics, Caltech, 161-33, Pasadena, California 91125 (United States)
- Instituto de Estructura de la Materia, Consejo Superior de Investigaciones Cientificas, Serrano 123, 28006 Madrid (Spain)
We examine isovector and isoscalar neutron-proton correlations in an exactly solvable model based on the algebra SO(8). We look particularly closely at Gamow-Teller strength and double {beta} decay, both to isolate the effects of the two kinds of pairing and to test two approximation schemes: the renormalized neutron-proton quasiparticle random phase approximation (QRPA) and generalized BCS theory. When isoscalar pairing correlations become strong enough a phase transition occurs and the dependence of the Gamow-Teller {beta}{sup +} strength on isospin changes in a dramatic and unfamiliar way, actually increasing as neutrons are added to an N=Z core. Renormalization eliminates the well-known instabilities that plague the QRPA as the phase transition is approached, but only by unnaturally suppressing the isoscalar correlations. Generalized BCS theory, on the other hand, reproduces the Gamow-Teller strength more accurately in the isoscalar phase than in the usual isovector phase, even though its predictions for energies are equally good everywhere. It also mixes T=0 and T=1 pairing, but only on the isoscalar side of the phase transition. {copyright} {ital 1997} {ital The American Physical Society}
- Research Organization:
- California Institute of Technology (CalTech), Pasadena, CA (United States)
- DOE Contract Number:
- FG03-88ER40397; FG05-94ER40827
- OSTI ID:
- 541980
- Journal Information:
- Physical Review, C, Vol. 55, Issue 4; Other Information: PBD: Apr 1997
- Country of Publication:
- United States
- Language:
- English
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