J/psi polarization at hadron colliders in nonrelativistic QCD

Abstract

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. ${}^3{S}_1[1,8]$, ${}^1{S}_0[8]$, and ${}^3{P}_J[8]$. We find the ${}^3{P}_J[8]$ 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 ${}^3{S}_1[8]$ and ${}^3{P}_J[8]$ channels, which results in mainly the unpolarized (even slightly longitudinally polarized) $J/psi$. This may give a possible solution to the long-standing $J/psi$ polarization puzzle. Predictions for $J/psi$ polarization at the LHC are also presented.

Comments: Published version, references updated