Abstract
The quantum numbers of the X(3872) meson are determined to be J(PC)=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 J(PC)=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.
Highlights
It has been almost ten years since the narrow Xð3872Þ state was discovered in Bþ decays by the Belle experiment [1,2]
The CDF experiment analyzed three-dimensional (3D) angular correlations in a relatively high-background sample of 2292 Æ 113 inclusively reconstructed Xð3872Þ ! þÀJ=c, J=c ! þÀ decays dominated by prompt production in pp" collisions
The reconstruction of the full decay chain resulted in a small background and polarized Xð3872Þ mesons, making their helicity angle (X) and orientation of their decay plane (X) sensitive to JPC as well
Summary
It has been almost ten years since the narrow Xð3872Þ state was discovered in Bþ decays by the Belle experiment [1,2]. The CDF experiment analyzed three-dimensional (3D) angular correlations in a relatively high-background sample of 2292 Æ 113 inclusively reconstructed Xð3872Þ ! A 2 fit of JPC hypotheses to the binned 3D distribution of the J=c and helicity angles (J=c , ) [14,15,16] and the angle between their decay planes (ÁJ=c ; 1⁄4 J=c À ) excluded all spinparity assignments except for 1þþ or 2Àþ.
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