$\mathrm{J}/\ddot{\mathrm{I}}ˆ$ production at low transverse momentum in p+p and d+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV

Abstract

We report on the measurement of $\mathrm{J}/\ddot{\mathrm{I}}ˆ$ production in the dielectron channel at mid-rapidity (|y|<1) in p+p and d+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV from the STAR experiment at the Relativistic Heavy Ion Collider. The transverse momentum $p_T$ spectra in p+p for $p_T$ < 4 GeV/c and d+Au collisions for $p_T$ < 3 GeV/c are presented. These measurements extend the STAR coverage for $\mathrm{J}/\ddot{\mathrm{I}}ˆ$ production in p+p collisions to low $p_T$. The $<p_T^2>$ from the measured $\mathrm{J}/\ddot{\mathrm{I}}ˆ$ invariant cross section in p+p and d+Au collisions are evaluated and compared to similar measurements at other collision energies. The nuclear modification factor for $\mathrm{J}/\ddot{\mathrm{I}}ˆ$ is extracted as a function of $p_T$ and collision centrality in d+Au and compared to model calculations using the modified nuclear Parton Distribution Function and a final-state $\mathrm{J}/\ddot{\mathrm{I}}ˆ$ nuclear absorption cross section.