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Deciphering the $X(3872)$ via its polarization in prompt production at the CERN LHC

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 Added by Bernd Kniehl
 Publication date 2019
  fields
and research's language is English




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Based on the hypothesis that the $X(3872)$ exotic hadron is a mixture of $chi_{c1}(2P)$ and other states and that its prompt hadroproduction predominately proceeds via its $chi_{c1}(2P)$ component, we calculate the prompt-$X(3872)$ polarization at the CERN LHC through next-to-leading order in $alpha_s$ within the factorization formalism of nonrelativistic QCD, including both the color-singlet $^3!P_1^{[1]}$ and color-octet $^3!S_1^{[8]}$ $cbar c$ Fock states. We also consider the polarization of the $J/psi$ produced by the subsequent $X(3872)$ decay. We predict that, under ATLAS, CMS, and LHCb experimental conditions, the $X(3872)$ is largely longitudinally polarized, while the $J/psi$ is largely transversely polarized. We propose that the LHC experiments perform such polarization measurements to pin down the nature of the $X(3872)$ and other $X$, $Y$, $Z$ exotic states with non-zero spin.



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The production of the X(3872) as a hadronic molecule in hadron colliders is clarified. We show that the conclusion of Bignamini et al., Phys. Rev. Lett. 103 (2009) 162001, that the production of the X(3872) at high $p_T$ implies a non-molecular structure, does not hold. In particular, using the well understood properties of the deuteron wave function as an example, we identify the relevant scales in the production process.
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