Determination of the X(3872) meson quantum numbers

The quantum numbers of the X(3872) meson are determined to be JPC=1 ⁺⁺ based on angular correlations in B ⁺→X(3872)K ⁺ decays, where X(3872)→π ⁺π ^-J/ψ and J/ψ→μ ⁺μ ^-. The data correspond to 1.0 fb ^-1 of pp collisions collected by the LHCb detector. The only alternative assignment allowed by previous measurements JPC=2 ^{- +} 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.