Measurements of ψ(2S) and X(3872) → J/ψπ ⁺ π ⁻ production in pp collisions at 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 ψ(2S), in the decay mode J/ψπ ⁺ π ⁻, measured using 11.4 fb⁻¹ of pp collisions at s√=8s=8 TeV by the ATLAS detector at the LHC. The ratio of cross-sections X(3872)/ψ(2S) is also given, separately for prompt and non-prompt components, as well as the non-prompt fractions of X(3872) and ψ(2S). Assuming independent single effective lifetimes for non-prompt X(3872) and ψ(2S) production gives

R_B=B(B→X(3872)+any)B(X(3872)→J/ψπ⁺π⁻)B(B→ψ(2S)+any)B(ψ(2S)→J/ψπ+π−)=(3.95±0.32(stat)±0.08(sys))×10−2RB=B(B→X(3872)+any)B(X(3872)→J/ψπ+π−)B(B→ψ(2S)+any)B(ψ(2S)→J/ψπ⁺π⁻)=(3.95±0.32(stat)±0.08(sys))×10⁻²

separating short- and long-lived contributions, assuming that the short-lived component is due to B_c decays, gives R_B = (3.57 ± 0.33(stat) ± 0.11(sys)) × 10⁻², with the fraction of non-prompt X(3872) produced via B_c decays for p_T(X(3872)) > 10 GeV being (25 ± 13(stat) ± 2(sys) ± 5(spin))%. The distributions of the dipion invariant mass in the X(3872) and ψ(2S) decays are also measured and compared to theoretical predictions.