Determination of the X(3872) meson quantum numbers
LHCb collaboration: R. Aaij, C. Abellan Beteta, B. Adeva, M. Adinolfi,, C. Adrover, A. Affolder, Z. Ajaltouni, J. Albrecht, F. Alessio, M. Alexander,, S. Ali, G. Alkhazov, P. Alvarez Cartelle, A.A. Alves Jr, S. Amato, S. Amerio,, Y. Amhis, L. Anderlini, J. Anderson
TL;DR
This paper determines the quantum numbers of the X(3872) meson as JPC = 1++, using angular correlations in B+ decays, strongly rejecting the alternative JPC=2-+ and supporting exotic interpretations.
Contribution
It provides the first definitive measurement of the X(3872) quantum numbers, ruling out previous alternative assignments with high confidence.
Findings
X(3872) has quantum numbers JPC = 1++
Alternative JPC=2-+ is rejected with high confidence
Supports exotic nature of the X(3872) meson
Abstract
The quantum numbers of the X(3872) meson are determined to be JPC = 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, JPC=2-+, is rejected with a confidence level equivalent to more than eight Gaussian standard deviations using the likelihood-ratio test in the full angular phase space. This result favors exotic explanations of the X(3872) state.
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