Breit-Wigner phase is a fundamental property of a resonance

TL;DR

This paper introduces the Breit-Wigner phase beta as a fundamental property of resonances, directly related to S-matrix poles, and suggests including it in data tables for better resonance characterization.

Contribution

It proposes the Breit-Wigner phase beta as a new fundamental resonance property and recommends its inclusion in resonance data tables.

Findings

Beta is a reaction invariant related to Breit-Wigner parameters

Beta can be extracted from data using a simple method

Inclusion of beta enhances resonance data completeness

Abstract

In the course of devising a simple method for extraction of the S-matrix poles from the data, an additional fundamental resonance property emerged. It is a reaction invariant quantity, and since it is directly related to the Breit-Wigner parameters, we call it the Breit-Wigner phase beta. We propose that this beta is added in resonant data tables.