Breit-Wigner phase is a fundamental property of a resonance

Understand

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.