Massive-Evolution Effects on Charmonium Hadroproduction

TL;DR

This paper revises the evolution equations for fragmentation functions of heavy hadrons, affecting the extraction of color-octet matrix elements in J/psi production, with implications for high-energy QCD phenomenology.

Contribution

It introduces generalized mu^2 evolution equations that respect phase-space constraints, refining the analysis of charmonium hadroproduction within nonrelativistic QCD.

Findings

Revised evolution equations lead to shifts in fitted matrix elements.

Improved theoretical consistency with phase-space constraints.

Potential impact on predictions for charmonium production at colliders.

Abstract

The fragmentation functions D_{a -> H}(x,mu^2) of a heavy hadron H, with mass m_H, satisfy the phase-space constraint D_{a - > H}(x,mu^2)=0 for x < m_H^2/mu^2, which is violated by the naive mu^2 evolution equations. Using appropriately generalized mu^2 evolution equations, we reconsider the inclusive hadroproduction of prompt J/psi mesons with high transverse momenta in the framework of the factorization formalism of nonrelativistic quantum chromodynamics, and determine the resulting shifts in the values of the leading colour-octet matrix elements, which are fitted to data from the Fermilab Tevatron.