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Title: Neutron-proton correlations in an exactly solvable model

Abstract

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}

Authors:
 [1];  [2];  [3];  [4];  [5]
  1. Department of Physics and Astronomy, University of North Carolina, Chapel Hill, North Carolina 27599 (United States)
  2. Bartol Research Institute, University of Delaware, Newark, Deleware 19716 (United States)
  3. Institute of Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, Sofia-1784 (Bulgaria)
  4. Department of Physics, Caltech, 161-33, Pasadena, California 91125 (United States)
  5. Instituto de Estructura de la Materia, Consejo Superior de Investigaciones Cientificas, Serrano 123, 28006 Madrid (Spain)
Publication Date:
Research Org.:
California Institute of Technology (CalTech), Pasadena, CA (United States)
OSTI Identifier:
541980
DOE Contract Number:  
FG03-88ER40397; FG05-94ER40827
Resource Type:
Journal Article
Journal Name:
Physical Review, C
Additional Journal Information:
Journal Volume: 55; Journal Issue: 4; Other Information: PBD: Apr 1997
Country of Publication:
United States
Language:
English
Subject:
66 PHYSICS; NUCLEAR FORCES; NUCLEON-NUCLEON POTENTIAL; PROTON-NEUTRON INTERACTIONS; CORRELATIONS; GAMOW-TELLER RULES; DOUBLE BETA DECAY; SO-8 GROUPS; RENORMALIZATION; QUASI PARTICLES; RANDOM PHASE APPROXIMATION; BCS THEORY; PAIRING INTERACTIONS; PHASE TRANSFORMATIONS; ISOSPIN; INSTABILITY

Citation Formats

Engel, J, Pittel, S, Stoitsov, M, Vogel, P, and Dukelsky, J. Neutron-proton correlations in an exactly solvable model. United States: N. p., 1997. Web. doi:10.1103/PhysRevC.55.1781.
Engel, J, Pittel, S, Stoitsov, M, Vogel, P, & Dukelsky, J. Neutron-proton correlations in an exactly solvable model. United States. https://doi.org/10.1103/PhysRevC.55.1781
Engel, J, Pittel, S, Stoitsov, M, Vogel, P, and Dukelsky, J. 1997. "Neutron-proton correlations in an exactly solvable model". United States. https://doi.org/10.1103/PhysRevC.55.1781.
@article{osti_541980,
title = {Neutron-proton correlations in an exactly solvable model},
author = {Engel, J and Pittel, S and Stoitsov, M and Vogel, P and Dukelsky, J},
abstractNote = {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}},
doi = {10.1103/PhysRevC.55.1781},
url = {https://www.osti.gov/biblio/541980}, journal = {Physical Review, C},
number = 4,
volume = 55,
place = {United States},
year = {Tue Apr 01 00:00:00 EST 1997},
month = {Tue Apr 01 00:00:00 EST 1997}
}