Measurement of $\Upsilon$(1S+2S+3S) production in $p$$+$$p$ and Au$+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV

Understand

Measurements of bottomonium production in heavy ion and $p$$+$$p$ collisions at the Relativistic Heavy Ion Collider (RHIC) are presented.

• The inclusive yield of the three $\Upsilon$ states, $\Upsilon(1S+2S+3S)$, was measured in the PHENIX experiment via electron-positron decay pairs at midrapidity for Au$+$Au and $p$$+$$p$ collisions at $\sqrt{s_{_{NN}}}=200$ GeV.
• The $\Upsilon(1S+2S+3S)\rightarrow e^+e^-$ differential cross section at midrapidity was found to be $B_{\rm ee} d\sigma/dy =$ 108 $\pm$ 38 (stat) $\pm$ 15(syst) $\pm$ 11 (luminosity) pb in $p$$+$$p$ collisions.
• The nuclear modification factor in the 30\% most central Au$+$Au collisions indicates a suppression of the total $\Upsilon$ state yield relative to the extrapolation from $p$$+$$p$ collision data.