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 √s̅ = 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(Β → 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 while 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.



Hadrons--Scattering, Pions--Decay, Transverse momentum, Large Hadron Collider (France and Switzerland),


CC BY 4.0 (Attribution), ©2017 CERN, for the ATLAS Collaboration