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arXiv · 2203.11056

Mass and width of an unstable particle

Scott Willenbrock
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Abstract

We show that the mass and width of an unstable particle are precisely defined by the pole in the complex energy plane, $\mu = m - (i/2)\Gamma$, by identifying the width, $\Gamma$, with the particle's decay rate and the mass, $m$, with the oscillatory frequency. We find that the physical $Z$ boson mass lies 26 MeV below its quoted value, while the physical $W$ boson mass lies 20 MeV below. We also clarify the various Breit-Wigner formulae that are used to describe a resonance.

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Scott Willenbrock. 2022-03-21. Mass and width of an unstable particle. https://arxiv.org/abs/2203.11056

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