Axial-vector exchange contribution to the Hyperfine Splitting

Abstract

We revisit the contribution of axial-vector mesons to the hyperfine splitting of muonic hydrogen. We focus our attention on the doubly-virtual asymptotic behavior of the relevant form factors of axial-vector mesons, together with their coupling to nucleons based on resonance saturation and short-distance constraints. Among others, we find significant differences with respect to previous studies, including an opposite sign and a $\sim 50\%$ effect of the doubly-virtual high-energy behavior.

Comments: 15 pages +references, 2 figures, 4 tables. Matches published version