Physical review / D 102(7), 072005 (1-14) (2020). doi:10.1103/PhysRevD.102.072005
We present various properties of the production of the $X(3872)$ and $ψ(2S)$ states based on $10.4 fb^{−1}$ collected by the D0 experiment in Tevatron $p\bar{p}$ collisions at $\sqrt{s}=1.96 TeV$. For both states, we measure the nonprompt fraction $f_{NP}$ of the inclusive production rate due to decays of $b$-flavored hadrons. We find the $f_{NP}$ values systematically below those obtained at the LHC. The fNP fraction for $ψ(2S)$ increases with transverse momentum, whereas for the $X(3872)$ it is constant within large uncertainties, in agreement with the LHC results. The ratio of prompt to nonprompt $ψ(2S)$ production, $(1−f_{NP})/f_{NP}$, decreases only slightly going from the Tevatron to the LHC, but for the $X(3872)$, this ratio decreases by a factor of about 3. We test the soft-pion signature of the $X(3872)$ modeled as a weakly bound charm-meson pair by studying the production of the $X(3872)$ as a function of the kinetic energy of the $X(3872)$ and the pion in the $X(3872)π$ center-of-mass frame. For a subsample consistent with prompt production, the results are incompatible with a strong enhancement in the production of the $X(3872)$ at the small kinetic energy of the $X(3872)$ and the π in the $X(3872)π$ center-of-mass frame expected for the $X$+soft-pion production mechanism. For events consistent with being due to decays of $b$ hadrons, there is no significant evidence for the soft-pion effect, but its presence at the level expected for the binding energy of 0.17 MeV and the momentum scale $Λ=M(π)$ is not ruled out.
Published by Inst.302363, Melville, NY