Analysis of the $ \boldsymbol{\gamma\gamma \to D\bar D}$ reaction and the $D\bar{D}$ bound state

TL;DR

This paper studies the gamma-gamma to D D-bar reaction, revealing a possible bound D D-bar state near threshold through data fitting, but emphasizes the need for more precise measurements to confirm its properties.

Contribution

It introduces a model incorporating D D-bar final state interactions to identify a bound state near threshold, based on experimental data fitting.

Findings

Good reproduction of Belle and BaBar data

Evidence for a D D-bar bound state near threshold

Uncertainty remains due to data precision

Abstract

In this work, we investigate the reaction of $\gamma\gamma \to D\bar{D}$, taking into account the s-wave $D\bar{D}$ final state interaction. By fitting to the $D\bar{D}$ invariant mass distributions measured by the Belle and BaBar Collaborations, we obtain a good reproduction of the data by means of a $D\bar{D}$ amplitude that produces a bound $D\bar{D}$ state with $I=0$ close to threshold. The error bands of the fits indicate, however, that more precise data on this reaction are needed to be more assertive about the position and width of such state.