Invariant mass distribution of opposite-sign dimuons in the rapidity regions $-4.46 < y_{\rm cms} < -2.96$ (top) and $2.03 < y_{\rm cms} < 3.53$ (bottom) in p-Pb collisions. In each case, the full curve shows the total fit function and the dashed curves the signal component for the three $\Upsilon$ states (see text for details).