Speaker
Dr
Leszek Kosarzewski
(Czech Technical University in Prague)
Description
$\Upsilon$ states can be used to study the properties of the quark-gluon plasma created in heavy-ion collisions. At sufficiently high temperature, $\Upsilon$ mesons dissociate in the plasma as a result of the Debye-like screening of the strong force. Due to their different binding energies, the ground and excited $\Upsilon$ states are expected to dissociate in a sequential pattern.
However, other effects, such as the influence of Cold Nuclear Matter (CNM), need to be taken into account when interpreting the $\Upsilon$ suppression observed in heavy-ion collisions.
Furthermore, the quarkonium production mechanism in elementary collisions is not yet fully understood.
This can be studied by comparing experimental measurements of $\Upsilon$ production in p+p collisions to theoretical calculations.
In addition, the dependence of the $\Upsilon$ yield on charged particle multiplicity can be used to study the interplay between hard and soft processes.
In this talk, we will present recent $\Upsilon$ measurements with the STAR experiment. The $\Upsilon$ transverse momentum and rapidity spectra in $500\:\mathrm{GeV}$ p+p collisions will be compared to model calculations. In addition, the normalized $\Upsilon$ yield vs. normalized charged particle multiplicity will be presented and compared to results from other experiments and models. The nuclear modification factors for $\Upsilon(1S)$ and $\Upsilon(2S+3S)$ in Au+Au collisions as functions of centrality and transverse momentum will be shown and compared to LHC measurements. Also, the nuclear modification factor of $\Upsilon(1S+2S+3S)$ as a function of rapidity measured in p+Au collisions will be presented for quantifying the CNM effects.
Primary author
Dr
Leszek Kosarzewski
(Czech Technical University in Prague)
