| Abstract: | We present measurements of the differential production cross sections of the
inclusive $J/psi$ meson as a function of transverse momentum
($p_{T}^{J/psi}$) using the $mu^{+}mu^{-}$ and $e^{+}e^{-}$ decay channels
in proton+proton collisions at center-of-mass energies of 510 and 500 GeV,
respectively, recorded by the STAR detector at the Relativistic Heavy Ion
Collider. The measurement from the $mu^{+}mu^{-}$ channel is for 0 $<
p_{T}^{J/psi} <$ 9 GeV/$c$ and rapidity range $|y^{J/psi}| < $ 0.4, and that
from the $e^{+}e^{-}$ channel is for 4 $< p_{T}^{J/psi} <$ 20 GeV/$c$ and
$|y^{J/psi}| < $ 1.0. The $psi(2S)$ to $J/psi$ ratio is also measured for 4
$< p_{T}^{
m meson} <$ 12 GeV/$c$ through the $e^{+}e^{-}$ decay channel.
Model calculations, which incorporate different approaches toward the $J/psi$
production mechanism, are compared with experimental results and show
reasonable agreement within uncertainties. A more discriminating comparison to
theoretical models at low $p_T$ can be performed in the future, if the
calculations are carried out within our fiducial volume, eliminating the
uncertainty due to the $J/psi$ polarization. |
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