omega-rho^0 mixing as a possible origin of the hypothetical isospin non-conservation in the X(3872) --> pi^+ pi^- J/psi decay

TL;DR

This paper investigates the isospin non-conservation in X(3872) decay via omega-rho^0 mixing, suggesting the tetra-quark model aligns better with experimental data than the charmonium model.

Contribution

It proposes a mechanism involving omega-rho^0 mixing to explain the decay ratio, favoring the tetra-quark interpretation of X(3872).

Findings

Calculated decay ratio matches experimental data for tetra-quark model.

Charmonium model predicts a much larger ratio than observed.

Data supports tetra-quark structure over charmonium for X(3872).

Abstract

The ratio of branching fractions Br(X(3872) --> gamma J/psi)/ Br(X(3872) --> pi^+ pi^- J/psi) is studied by assuming that the X(3872) --> pi^+ pi^- J/psi decay proceeds through the rho^0 meson pole which is caused by the omega-rho^0 mixing. As the result, it is seen that the calculated ratio is compatible with the measured values of the ratio when X(3872) is an axial-vector tetra-quark state, while it would be much larger than the measurements when it is a charmonium. Therefore, the existing data on the ratio seem to favor the tetra-quark interpretation of X(3872) over the charmonium, although a small mixing of the charmonium is not excluded.