Suppression of $\mathrm{{\rm Y}}$(1S) at forward rapidity in Pb-Pb collisions at $\sqrt{s_{\mathrm{N}\mathrm{N}}}$ = 2.76 TeV

We report on the measurement of the inclusive $\mathrm{{\rm Y}}$(1S) production in Pb-Pb collisions at $\sqrt{s_{\mathrm{N}\mathrm{N}}}=2.76$ TeV carried out at forward rapidity ($2.5<y<4$) and down to zero transverse momentum using its ${\mu }^{+}{\mu }^{-}$ decay channel with the ALICE detector at the Large Hadron Collider. A strong suppression of the inclusive $\mathrm{{\rm Y}}$(1S) yield is observed with respect to pp collisions scaled by the number of independent nucleon-nucleon collisions. The nuclear modification factor, for events in the 0-90$\mathrm{\%}$ centrality range, amounts to $0.30\pm0.05{\rm (stat)}\pm0.04{\rm (syst)}$\mathrm{.}Theobserved$\Upsilon$(1S) suppression increases with the centrality of the collision and is more pronounced than in corresponding mid-rapidity measurements. Our results are compared with model calculations, which are found to underestimate the measured suppression and fail to reproduce its rapidity dependence.