Is the Up-Quark Mass Zero?

Abstract

We consider, within the framework of current algebra, the possibility that the up-quark mass vanishes (as an alternative to the axion). We argue that the contrary current-algebra value, $\frac{{m}_{u}}{{m}_{d}}=\frac{1}{1.8}$, is unreliable. A critical analysis leads to the conclusion that ${m}_{u}=0$ is not unreasonable and furthermore leads to a surprisingly good prediction for the $\ensuremath{\delta}$-meson mass.