Factorization breaking in high-transverse-momentum charged-hadron production at the Tevatron?

TL;DR

This paper compares Tevatron measurements of high-p_T charged-hadron production with QCD predictions, finding significant discrepancies at high p_T that may challenge the fundamental factorization theorem of QCD.

Contribution

It provides the first detailed comparison revealing potential breakdown of factorization in high-p_T hadron production at Tevatron energies.

Findings

Data significantly exceeds QCD predictions at high p_T

Discrepancies cannot be explained by additional particle production

Potential challenge to the validity of the factorization theorem

Abstract

We compare the transverse momentum (p_T) distribution of inclusive light-charged-particle production measured by the CDF Collaboration at the Fermilab Tevatron with the theoretical prediction evaluated at next-to-leading order in quantum chromodynamics (QCD) using fragmentation functions recently determined through a global data fit. While, in the lower p_T range, the data agree with the prediction within the theoretical error or slightly undershoot it, they significantly exceed it in the upper p_T range, by several orders of magnitude at the largest values of p_T, where perturbation theory should be most reliable. This disagreement is too large to be remedied by introducing additional produced particles into the calculation, and potentially challenges the validity of the factorization theorem on which the parton model of QCD relies. Clearly, a breakdown of the factorization theorem, being a fundamental property of QCD, would be extremely difficult to understand.