J/psi production in hadron colliders

One long-standing puzzle in heavy quarkonium phenomenology is the polarization of prompt J/psi produced with large transverse momentum (p_T) at hadron colliders. Calculations based on the nonrelativistic QCD (NRQCD) factorization usually predict transverse polarization, which is inconsistent with measurements. We compute leading-power fragmentation corrections to J/psi production that result in substantial changes to the predictions of NRQCD factorization. We find that these corrections lead to predictions of near-zero J/psi polarization at large p_T, which is in much improved agreement with measurements.