What can radiative decays of the X(3872) teach us about its nature?

TL;DR

This paper investigates the radiative decays of the X(3872) under the molecular hypothesis, concluding that these decays are not sensitive to its long-range structure and do not conflict with a D-D* molecular composition.

Contribution

It provides an effective field theory analysis showing radiative decays are insensitive to the X(3872)'s long-range structure, challenging previous assumptions.

Findings

Radiative decays are weakly sensitive to the X(3872)'s structure.

The decay ratio does not conflict with a D-D* molecular wave function.

The molecular hypothesis remains consistent with experimental decay ratios.

Abstract

Starting from the hypothesis that the X(3872) is a $D\bar D^*$ molecule, we discuss the radiative decays of the X(3872) into $\gamma J/\psi$ and $\gamma\psi'$ from an effective field theory point of view. We show that radiative decays are very weakly sensitive to the long-range structure of the X(3872). In particular, contrary to earlier claims, we argue that the experimentally determined ratio of the mentioned branching fractions is not in conflict with a wave function of the X(3872) that is dominated by the $D\bar D^*$ hadronic molecular component.