UC Santa Cruz

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.