© 2015, CERN for the benefit of the LHCb collaboration. The production of the η<inf>c</inf>(1S) state in proton-proton collisions is probed via its decay to the pp final state with the LHCb detector, in the rapidity range 2.0 < y < 4.5 and in the meson transverse-momentum range p<inf>T</inf> > 6.5 GeV/c. The cross-section for prompt production of η<inf>c;</inf>(1S) mesons relative to the prompt J/ψ cross-section is measured, for the first time, to be σ<inf>ηc(1S)</inf>/σ<inf>J/ψ</inf> = 1.74±0.29±0.28±0. 18<inf>B</inf> at a centre-of-mass energy (Formula presented.) using data corresponding to an integrated luminosity of 0.7 fb<sup>-1</sup>, and σ<inf>ηc</inf>(1S)/σJ/ψ = 1.60±0.29±0.25±0.17<inf>B</inf> at (Formula presented.) using 2.0 fb<sup>-1</sup>. The uncertainties quoted are, in order, statistical, systematic, and that on the ratio of branching fractions of the η<inf>c</inf>(1S) and J/ψ decays to the pp final state. In addition, the inclusive branching fraction of b-hadron decays into η<inf>c</inf>(1S) mesons is measured, for the first time, to be B(b→η<inf>c</inf>X)=(4.88±0.64±0.29±0.67<inf>B</inf>)×<sup>10-3</sup>, where the third uncertainty includes also the uncertainty on the J/ψ inclusive branching fraction from b-hadron decays. The difference between the J/ψ and η<inf>c</inf>(1S) meson masses is determined to be 114.7±1.5±0.1MeV/c<sup>2</sup>.
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