# Radiative and pionic transitions $Z_c(4020)^0 \to X(3872) \gamma$ and $Z_c(4020)^\pm \to X(3872) \pi^\pm$

## TL;DR

This paper investigates the radiative and pionic transitions of the exotic $Z_c(4020)$ states to $X(3872)$, analyzing their decay mechanisms and estimating transition rates within a molecular state framework.

## Contribution

It provides the first detailed analysis of the transition rates of $Z_c(4020)$ to $X(3872)$ via radiative and pionic processes assuming molecular structures.

## Key findings

- Transition rates are typically a few per mille.
- Peak transition rates occur near the vector meson pair threshold.
- Transitions involve decays of charmed vector mesons to pseudoscalar plus photon or pion.

## Abstract

The radiative transitions from the neutral exotic $Z_c(4020)^0$ resonance to $X(3872)$ with emission of a photon and the pionic transitions from the charged $Z_c(4020)^\pm$ to $X(3872)$ and a charged pion $\pi^\pm$ are considered for both charmoniumlike states being charmed meson-antimeson molecules. The underlying processes for these transitions are the decays of the charmed vector meson to pseudoscalar plus a photon or a pion. It is found that the discussed transition rates typically amount to a branching fraction of several permil with a peak at the vector meson pair threshold.