Measurement of J/Ψ production in pp collisions at $\sqrt{s}=7$ TeV

The production of $J\hspace{-1.5pt}/\hspace{-0.45pt}\psi$ mesons in proton–proton collisions at $\sqrt{s}=7\ensuremath {~\mathrm {TeV}}$ is studied with the LHCb detector at the LHC. The differential cross-section for prompt $J\hspace{-1.5pt}/\hspace{-0.45pt}\psi$ production is measured as a function of the $J\hspace{-1.5pt}/\hspace{-0.45pt}\psi$ transverse momentum pT and rapidity y in the fiducial region ${\ensuremath{p_{\mathrm{T}}}}\in[0;14]{\ensuremath{~\mathrm{GeV}\mskip-2mu/\mskip-1mu c}}$ and y∈[2.0;4.5]. The differential cross-section and fraction of $J\hspace{-1.5pt}/\hspace{-0.45pt}\psi$ from b-hadron decays are also measured in the same pT and y ranges. The analysis is based on a data sample corresponding to an integrated luminosity of 5.2 pb−1. The measured cross-sections integrated over the fiducial region are for prompt ${\ensuremath{J\hspace{-1.5pt}/\hspace{-0.45pt}\psi}}$ production and for $J\hspace{-1.5pt}/\hspace{-0.45pt}\psi$ from b-hadron decays, where the first uncertainty is statistical and the second systematic. The prompt ${\ensuremath{J\hspace{-1.5pt}/\hspace{-0.45pt}\psi}}$ production cross-section is obtained assuming no $J\hspace{-1.5pt}/\hspace{-0.45pt}\psi$ polarisation and the third error indicates the acceptance uncertainty due to this assumption.