On the two-photon decay width of the sigma meson

TL;DR

This paper calculates the two-photon decay width of the sigma meson as a quarkonium state, revealing it to be less than 1 keV due to destructive interference effects in the transition amplitude.

Contribution

It provides a detailed evaluation of the quark-loop diagram for the sigma meson decay, including a previously omitted term, refining the decay width estimate.

Findings

Decay width less than 1 keV for physical parameters

Destructive interference significantly reduces the decay width

Careful quark-loop calculation improves theoretical predictions

Abstract

We shortly report on the two-photon decay width of the light $\sigma$-meson interpreted as a quarkonium state. Results are given in dependence on the $\sigma$-mass and the constituent mass of the light quark. The triangle quark-loop diagram, responsible for the two-photon transition, is carefully evaluated: a term in the transition amplitude, often omitted in literature, results in destructive interference with the leading term. As a result we show that the two-photon decay width of the $\sigma $ in the quarkonium picture is less than 1 keV for the physical range of parameters.