Hi team, gh-17505 proposes to add a new continuous distribution to stats, the Relativistic Breit-Wigner distribution, which is used in high energy physics for modeling unstable particles. The addition of this distribution was first suggested in issue gh-6414 by contributor Andrew Fowlie (andrewfowlie), who is a physicist working in the area. Discussion faltered for several years but has picked up again recently. It has been determined that this is not a reparametrization or transformation of an existing distribution. Particle physicist and developer of relevant statistical software Hans Dembinski (HDembinski) recently provided context and voiced support for its inclusion in gh-6414. Hdembinski also pointed out that there is precedent for including distributions from high energy physics due to scipy.stats.crystalball. This seemed like a fun project to work on and a good excuse to try to refresh some long-faded physics knowledge so I pieced this together. Feedback is welcome at: https://github.com/scipy/scipy/pull/17505 Thanks, Albert