The radius of the rho meson determined from its decay constant

TL;DR

This paper develops a unified relativistic model to determine the rho meson's radius and decay constant, confirming the equality of electromagnetic and strong radii for the rho meson, based on experimental data.

Contribution

It introduces a method to calculate the rho meson's properties using parameters fixed from the pi meson, extending previous models to include the rho meson with a new free parameter.

Findings

Calculated rho meson decay constant matching experimental value

Determined the rho meson's mean square charge radius as 0.56±0.04 fm^2

Verified the conjecture of equality between electromagnetic and strong radii for the rho meson

Abstract

We present a unified model describing electroweak properties of the pi and rho mesons. Using a general method of relativistic parametrization of matrix elements of local operators, adjusted for the nondiagonal in total angular momentum case, we calculate the rho-meson lepton-decay constant f_rho using the same parameters of free constituent quarks that have ensured exclusively good results for the pi meson previously. The only free parameter, characterizing quark interactions, which include additional spin-spin contribution and hence differ from the $\pi$-meson case, is fixed by matching the decay constant to its experimental value. The mean square charge radius is calculated, <r^2_rho>=(0.56+-0.04) fm^2. This result verifies, for the rho-meson case, the conjecture of equality between electromagnetic and strong radii of hadrons tested previously for proton, pi and K mesons.