$R_{\mathrm{AA}}$ of the $\phi$ meson as a function of $\langle N_{\mathrm{part}} \rangle$ for $2.5< y< 4$, compared with the ALICE measurement for $|y|< 0.5$. All the midrapidity points have been displaced by $\npart$ = 10 for better visibility. Transparent boxes represent the uncorrelated systematic uncertainties at forward rapidity and the total systematic uncertainties (including correlated and uncorrelated components) at midrapidity The shaded red box represents the correlated systematic uncertainties at forward rapidity, the shaded blue box represents the normalization uncertainty at midrapidity. Results from PHENIX in Au-Au and Cu-Cu collisions at $\sqrt{s_\mathrm{NN}}$ = 200 GeV are also shown for comparison.