Measurement of $\mathrm{{\rm Y}}$ production in $pp$ collisions at $\sqrt{s}$= 13 TeV

The production cross-sections of $\mathrm{{\rm Y}}(1S)$, $\mathrm{{\rm Y}}(2S)$ and $\mathrm{{\rm Y}}(3S)$ mesons in proton-proton collisions at $\sqrt{s}$= 13 TeV are measured with a data sample corresponding to an integrated luminosity of $277 \pm 11$ $\mathrm{p}{\mathrm{b}}^{-1}$ recorded by the LHCb experiment in 2015. The $\mathrm{{\rm Y}}$ mesons are reconstructed in the decay mode $\mathrm{{\rm Y}}\to {\mu }^{+}{\mu }^{-}$. The differential production cross-sections times the dimuon branching fractions are measured as a function of the $\mathrm{{\rm Y}}$ transverse momentum, $p_{\mathrm{T}}$, and rapidity, $y$, over the range $0<p_{\mathrm{T}}<30$ GeV/c and $2.0<y<4.5$. The ratios of the cross-sections with respect to the LHCb measurement at $\sqrt{s}$= 8 TeV are also determined. The measurements are compared with theoretical predictions based on NRQCD.