Neutron Resonance Widths and the Porter-Thomas Distribution

TL;DR

This paper investigates how realistic couplings to decay channels affect the validity of the Porter-Thomas distribution for neutron widths, challenging previous assumptions of its universal applicability.

Contribution

It identifies specific terms in the effective Hamiltonian that violate orthogonal invariance, demonstrating their impact on the PTD's validity.

Findings

Coupling to decay channels significantly modifies the PTD.

Two terms in the Hamiltonian violate orthogonal invariance.

Realistic estimates show deviations from the PTD.

Abstract

Experimental evidence has recently put the validity of the Porter-Thomas distribution (PTD) for partial neutron widths into question. We identify two terms in the effective Hamiltonian that violate orthogonal invariance (the basis for the PTD). Both are due to the coupling to the decay channels. We show that realistic estimates for the coupling to the neutron channel and for non-statistical gamma decays yield significant modifications of the PTD.