Quarkonium measurements via the di-muon decay channel in $\rm p$+$\rm p$ and $\rm Au$+$\rm Au$ collisions with the STAR experiment

Abstract: We present the first $J/\psi$ and $\Upsilon$ 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 $J/\psi$ 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 $J/\psi$ suppression indicating dissociation; (ii) $J/\psi$ $R_{AA}$ 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 $\Upsilon(2S+3S)$ relative to $\Upsilon(1S)$ at RHIC compared to that at LHC.