What Does the Balance Function Measure?

Abstract

The balance function has been proposed to `clock' hadronization by measuring the charge-dependent correlation length on rapidity. According to the proposal a narrowed balance function would imply reduced hadron diffusion time and therefore delayed hadronization due to a long-lived prehadronic state, a quark-gluon plasma or QGP. I examine this chain of argument in the context of hadronization and rescattering. I then consider the algebraic structure of the balance function and its systematic dependence on the charge correlation length on rapidity. I conclude that the width of the balance function cannot determine a time interval from hadronization to kinetic decoupling, nor can the width determine the existence or temporal extent of a QGP.