Observation of an alternative $\chi_{c0}(2P)$ candidate in $e^+ e^- \rightarrow J/\psi D \bar{D}$

TL;DR

This study reports the observation of a new charmoniumlike state, X*(3860), in the process e+ e- → J/ψ D D̄, with detailed amplitude analysis and significance assessment based on Belle detector data.

Contribution

The paper presents the first observation of the X*(3860) state decaying to D D̄ with detailed amplitude analysis and quantum number determination.

Findings

X*(3860) observed with 6.5σ significance

Mass of X*(3860) is approximately 3862 MeV/c²

Width of X*(3860) is approximately 201 MeV

Abstract

We perform a full amplitude analysis of the process $e^+ e^- \rightarrow J/\psi D \bar{D}$, where $D$ refers to either $D^0$ or $D^+$. A new charmoniumlike state $X^*(3860)$ that decays to $D \bar{D}$ is observed with a significance of $6.5\sigma$. Its mass is ($3862^{+26}_{-32}{}^{+40}_{-13}$) MeV/$c^2$ and width is ($201^{+154}_{-67}{}^{+88}_{-82}$) MeV. The $J^{PC}=0^{++}$ hypothesis is favored over the $2^{++}$ hypothesis at the level of $2.5\sigma$. The analysis is based on the 980 $\mathrm{fb}^{-1}$ data sample collected by the Belle detector at the asymmetric-energy $e^+ e^-$ collider KEKB.