Measurements of $\psi (2S)$ and $X(3872)\to J\mathrm{/}\psi {\pi }^{+}{\pi }^{-}$ production in $pp$ collisions 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 $J\mathrm{/}\psi {\pi }^{+}{\pi }^{-}$, measured using 11.4 fb${}^{-1}$ of $pp$ collisions at $\sqrt{s}=8$ TeV by the ATLAS detector at the LHC. The ratio of cross-sections $X(3872)\mathrm{/}\psi (2S)$ is also given, separately for prompt and non-prompt components, as well as the non-prompt fractions of $X(3872)$ and $\psi (2S)$. Assuming independent single effective lifetimes for non-prompt $X(3872)$ and $\psi (2S)$ production gives $R_B = \frac{$\mathcal{B}$(B \rightarrow X(3872)$\text{ + any}$) $\mathcal{B}$(X(3872 \rightarrow J/\psi\pi^+\pi^-)}{$\mathcal{B}$(B \rightarrow \psi(2S)$\text{ + any}$) $\mathcal{B}$(\psi(2S) \rightarrow J/\psi\pi^+\pi^-)} = (3.95 \pm 0.32 $(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})$ \pm 0.08$(\mathrm{s}\mathrm{y}\mathrm{s})$) \times 10^{-2}$, while separating short- and long-lived contributions, assuming that the short-lived component is due to $B_c$ decays, gives $R_B = (3.57 \pm 0.33$(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})$ \pm 0.11$(\mathrm{s}\mathrm{y}\mathrm{s})$) \times 10^{-2}$,withthefractionofnon-prompt$X(3872)$producedvia$B_c$decaysfor$p_$\mathrm{T}$(X(3872)) > 10$GeVbeing$(25 \pm 13$(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})$ \pm 2$(\mathrm{s}\mathrm{y}\mathrm{s})$ \pm 5$(\mathrm{s}\mathrm{p}\mathrm{i}\mathrm{n})$)%$. The distributions of the dipion invariant mass in the $X(3872)$ and $\psi (2S)$ decays are also measured and compared to theoretical predictions.