Suppression of \(\Upsilon\)(1S) at forward rapidity in Pb-Pb collisions at \(\sqrt{s_{\rm NN}}\) = 2.76 TeV

Abstract

We report on the measurement of the inclusive \(\Upsilon\).1S) production in Pb-Pb collisions at \(\sqrt{s_{\rm NN}}=2.76\) 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 \(\Upsilon\).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\).%\) centrality range, amounts to \(0.30\pm0.05{\rm (stat)}\pm0.04{\rm (syst)}\). The observed \(\Upsilon\).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.