Polarization and cross section of midrapidity J/ψ production in p+p collisions at √s = 510 GeV

The PHENIX experiment has measured the spin alignment for inclusive J/ψ→e+e− decays in proton-proton collisions at √s=510  GeV at midrapidity. The angular distributions have been measured in three different polarization frames, and the three decay angular coefficients have been extracted in a full two-dimensional analysis. Previously, PHENIX saw large longitudinal net polarization at forward rapidity at the same collision energy. This analysis at midrapidity, complementary to the previous PHENIX results, sees no sizable polarization in the measured transverse momentum range of 0.0<10.0  GeV/c. The results are consistent with a previous one-dimensional analysis at midrapidity at √s=200  GeV. The transverse-momentum-dependent cross section for midrapidity J/ψ production has additionally been measured, and after comparison to world data, a simple logarithmic dependence of the cross section on √s was found.