The $\rho$ meson magnetic dipole moment from BaBar $e^+e^- \to \pi^+ \pi^-\pi^0 \pi^0 $ cross section measurement

TL;DR

This paper determines the magnetic dipole moment of the rho meson using BaBar data on e+e- collisions, employing a vector meson dominance model to improve previous estimates with more precise data and theoretical consistency.

Contribution

The study provides a more accurate and gauge-invariant determination of the rho meson magnetic dipole moment using detailed BaBar data and an improved theoretical model.

Findings

Measured rho meson magnetic dipole moment as 2.7 ± 0.3 e/2m_rho

Enhanced previous estimates with better data and theoretical treatment

Validated the vector meson dominance model at these energies

Abstract

We obtain the value of the magnetic dipole moment of the $\rho$ meson, using data from the BaBar Collaboration for the $e^{+} e^{-} \to \pi^+ \pi^- 2 \pi^0$ process. The considered center of mass energy range is from 0.9 to 1.8 GeV. We describe the $\gamma^* \to 4\pi$ vertex using a vector meson dominance model, including the intermediate resonant contributions relevant at these energies. We find $\mu_\rho = 2.7 \pm 0.3 $ in $e/2 m_\rho$ units. We improve on the previous extracted value, where preliminary data from the same collaboration was used, by considering definite data, better grounded values of the parameters involved and explicit gauge invariant description of the process.