Determination of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>X</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:mn>3872</mml:mn><mml:mo stretchy="false">)</mml:mo></mml:math>Meson Quantum Numbers
Abstract
The quantum numbers of the $X(3872)$ meson are determined to be ${J}^{PC}={1}^{++}$ based on angular correlations in ${B}^{+}\ensuremath{\rightarrow}X(3872){K}^{+}$ decays, where $X(3872)\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}J/\ensuremath{\psi}$ and $J/\ensuremath{\psi}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$. The data correspond to $1.0\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of $pp$ collisions collected by the LHCb detector. The only alternative assignment allowed by previous measurements ${J}^{PC}={2}^{\ensuremath{-}+}$ is rejected with a confidence level equivalent to more than 8 Gaussian standard deviations using a likelihood-ratio test in the full angular phase space. This result favors exotic explanations of the $X(3872)$ state.
Not yet translated