Production measurements of $\psi(2S)$ and $X(3872) \to J/\psi\pi^+\pi^-$ at $\sqrt{s} = 8$ TeV with the ATLAS detector

Differential cross-sections are presented for the prompt and non-prompt production of the hidden-charm states $X(3872)$ and $\psi(2S)$, in the decay mode $J/\psi\pi^+\pi^-$, measured using 11.4 fb$^{-1}$ of $pp$ collisions at $\sqrt{s} = 8$ TeV taken by the ATLAS detector at the LHC. The ratios of these cross-sections are also shown, separately for prompt and non-prompt components, as well as the non-prompt fractions of $X(3872)$ and $\psi(2S)$. The non-prompt production of $X(3872)$ was separated into short-lived and long-lived contributions, from which the ratio of the branching fractions $R_B = \frac{Br(B \rightarrow X(3872)) Br(X(3872) \rightarrow J/\psi\pi^+\pi^-)}{Br(B \rightarrow \psi(2S)) Br(\psi(2S) \rightarrow J/\psi\pi^+\pi^-)}$ was found to be $(3.57 \pm 0.33 \mathrm{(stat)} \pm 0.11\mathrm{(sys)})\%$. Under the assumption that the short-lived component is due to $B_c$ decays, the fraction of non-prompt $X(3872)$ production proceeding via $B_c$ decays for $p_{T}(X(3872)) > 10$ GeV is found to be $(25 \pm 13\mathrm{(stat)} \pm 2\mathrm{(sys)} \pm 5\mathrm{(spin)})\%$. The distributions of the di-pion invariant mass in the $X(3872)$ and $\psi(2S)$ decays are also measured and compared to expectations.