Observation of X (3872) production in pp collisions at √s =7 TeV

Using 34.7 pb^-1 of data collected with the LHCb detector, the inclusive production of the X(3872) meson in pp collisions at √s = 7 TeV is observed for the first time. Candidates are selected in the X(3872)→J/ψπ⁺π^- decay mode, and used to measure σ (pp→ X(3872)+ anything)B(X(3872) → J/ψπ⁺π^-)=5.4±1.3(stat)±0.8(sust) nb, where σ(pp→X(3872)+anything) is the inclusive production cross section of X(3872) mesons with rapidity in the range 2.5-4.5 and transverse momentum in the range 5-20 GeV/c. In addition the masses of both the X(3872) and ψ(2S) mesons, reconstructed in the J/ψπ⁺π^- final state, are measured to be m_X(3872) = 3871.95±0.48(stat)±0.12(syst) MeV/c² and m_ψ(2S)=3686.12 ±0.06(stat) ±0.010 (syst) MeV/c².