0000000001163903
AUTHOR
Bertrand Desplanques
Parity non-conservation at the peak of p-resonances in low-energy neutron-nucleus scattering
Abstract Parity-non-conserving effects at the top of ρ-wave resonances in low-energy neutron-nucleus scattering are revisited in view of recent measurements in 238 U and 232 Th. This is done in the framework of the valence model. A quite simple expression in terms of the strength of the neutron-nucleus parity-non-conserving force is derived for the P ( E p ) asymmetry. The result, which is independent on the nucleus, can usefully be considered as a benchmark for those effects. Comparison of experiment to theory confirms earlier conclusions, namely the expected strength of the neutron-nucleus parity-non-conserving force is much too low to account for observations in this approach, even if th…
Is the standard, parity-non-conserving, nucleon-nucleus interaction a surface one?
Abstract Claims that the standard single-particle, parity-non-conserving, nucleon-nucleus interaction, V pnc = ct · 1 2 { σ · p , ϱ(r)} , is a surface one are considered. It is shown that examination of integrands entering some quantity involving Vpnc leads to quite puzzling results. These are further supported by a similar examination for a term [ σ · p , ϱ(r) ] which is odd under time-reversal, but has a priori a well-defined surface character. Alternative approaches to determine whether Vpnc is a surface or volume interaction are developed, based on using wave functions as test functions. From these approaches, the volume character of Vpnc is unambiguous.
ββ2ν decay in 48Ca
[EN] A schematic study of the bb2n decay of 48Ca is made in a shell-model approach. The emphasis is especially put on the role of the spin-orbit potential in relation with the contribution of other terms in the strong interaction. This is discussed with a particular attention to the behavior of these ones under the SU(4) symmetry. Different methods in calculating the transition amplitude are also looked at with the aim to determine their reliability and, eventually, why they do not work. Further aspects relative to the failure of the operator expansion method to reproduce the results of more elaborate calculations are examined.