Neutron width statistics in a realistic resonance-reaction model

The statistical model of compound nucleus reactions is widely used in nuclear science, astrophysics, and nuclear technology. A recent experiment [1] found that the distributions of reduced neutron widths for Pt isotopes deviate from the Porter-Thomas distribution (PTD). This finding contradicts the statistical model expectation, and several explanations have been proposed [2-4]. We have studied resonance width statistics for $s$-wave neutron scattering off $^{194}$Pt within a model that combines the statistical description of the compound nucleus with a realistic description of the neutron channel [5]. We find that the reduced neutron width distribution agrees with the PTD for a large range of the model parameters, if the energy dependence of the average neutron widths is correctly described. We identify a parameter range where a near-threshold bound or virtual state of the neutron channel distorts the average neutron width [2], leading to apparent PTD violation if the usual analysis is used. [1] P.E. Koehler {\em et al}, PRL {\bf 105}, 072502 (2010) [2] H.A. Weidenm\"uller, PRL {\bf 105}, 232501 (2010) [3] G.L. Celardo {\em et al}, PRL {\bf 106}, 042501 (2011) [4] A. Volya {\em et al.}, PRL {\bf 115}, 052501 (2015) [5] P. Fanto, G.F. Bertsch, and Y. Alhassid, arXiv:1710.00792