Inclusive $\Upsilon$ production in p--Pb collisions at $\sqrt{s_{\rm NN}}$ = 8.16 TeV with ALICE at the LHC

Abstract

In order to disentangle CNM effects from the ``hot'' QGP effects, quarkonium production is studied in p--Pb collisions in which QGP formation is not expected. ALICE has measured the $\Upsilon$ production in p--Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV at backward ($-$4.46 $<y_{\rm cms}<$ $-$2.96) and forward (2.03 $< y_{\rm cms}<$ 3.53) rapidity down to zero transverse momentum. At forward rapidity, a suppression of $\Upsilon$(1S) production in p--Pb collisions is observed compared to the binary-scaled yield in pp collisions in the same kinematic domain while at backward rapidity no significant suppression or enhancement is found within the experimental uncertainties. In 2016, the LHC delivered p--Pb collisions at $\sqrt{s_{\rm NN}}$ = 8.16 TeV with higher integrated luminosity compared to the data collected at $\sqrt{s_{\rm NN}}$ = 5.02 TeV, which allowed a more detailed study of the bottomonium production in p--Pb collisions. We report on the inclusive $\Upsilon$(1S) production as a function of rapidity, transverse momentum ($p_{\rm T}$) and centrality of the collision and compare the results with those obtained at $\sqrt{s_{\rm NN}}$ = 5.02 TeV. Theoretical model predictions as a function of $y_{\rm cms}$ and $p_{\rm T}$ are also discussed. The results of $\Upsilon$(2S) suppression integrated over $y_{\rm cms}$, $p_{\rm T}$ and centrality are also reported and compared to the corresponding $\Upsilon$(1S) measurement.