Determination of the X(3872) meson quantum numbers
R. Aaij et al.
Accepted
\noindent The quantum numbers of the $X(3872)$ meson are determined to be $J^{PC} = 1^{++}$ based on angular correlations in $B^+\to X(3872) K^+$ decays, where $X(3872)\to \pi^+\pi^- J/\psi$ and $J/\psi \to\mu^+\mu^-$. The data correspond to 1.0 fb$^{-1}$ of $pp$ collisions collected by the LHCb detector. The only alternative assignment allowed by previous measurements, $J^{PC}=2^{-+}$, is rejected with a confidence level equivalent to more than eight Gaussian standard deviations using a likelihood-ratio test in the full angular phase space. This result favors exotic explanations of the $X(3872)$ state.