J/psi polarization at hadron colliders in nonrelativistic QCD

Understand

With nonrelativistic QCD factorization, we present a full next-to-leading order computation of the polarization observable for $J/psi$ production at hadron colliders including all important Fock states, i.e.

• $^3S_1[1,8]$, $^1S_0[8]$, and $^3P_J[8]$.
• We find the $^3P_J[8]$ channel contributes a positive longitudinal component and a negative transverse component.
• So the $J/psi$ polarization puzzle may be understood as the transverse components canceling between $^3S_1[8]$ and $^3P_J[8]$ channels, which results in mainly the unpolarized (even slightly longitudinally polarized) $J/psi$.