Color-Octet Fragmentation and the ψ^′ Surplus at the Fermilab Tevatron

The production rate of prompt ψ^′'s at large transverse momentum at the Fermilab Tevatron is larger than theoretical expectations by about a factor of 30. As a solution to this puzzle, we suggest that the dominant ψ^′ production mechanism is the fragmentation of a gluon into a cc̅ pair in a pointlike color-octet S-wave state, which subsequently evolves nonperturbatively into a ψ^′ plus light hadrons. This contribution to the fragmentation function is enhanced by a short-distance factor of 1/α_s², which may compensate for its suppression by v⁴, where v is the relative momentum of the charm quark in the ψ^′.