Quarkonium measurements via the di-muon decay channel in $\mathrm{p}$+$\mathrm{p}$ and $\mathrm{A}\mathrm{u}$+$\mathrm{A}\mathrm{u}$ collisions with the STAR experiment

We present the first $J\mathrm{/}\psi$ and $\mathrm{{\rm Y}}$ measurements in the di-muon decay channel at mid-rapidity at RHIC using the newly installed Muon Telescope Detector. In p$+$p collisions at $\sqrt{s}=500$~GeV, inclusive $J\mathrm{/}\psi$ cross section can be described by CGC+NRQCD and NLO NRQCD model calculations for $0<p_T<20$~GeV/$c$. In Au$+$Au collisions at $\sqrt{s_{NN}}=200$~GeV, we observe (i) clear $J\mathrm{/}\psi$ suppression indicating dissociation; (ii) $J\mathrm{/}\psi$ $R_{AA}$ can be qualitatively described by transport models including dissociation and regeneration with a tension at high $p_T$; and (iii) hint of less melting of $\mathrm{{\rm Y}}(2S+3S)$ relative to $\mathrm{{\rm Y}}(1S)$ at RHIC compared to that at LHC.