Constraints on $s-\bar{s}$ asymmetry of the proton in chiral effective theory

Abstract

We compute the $s-\bar{s}$ asymmetry in the proton in chiral effective theory, using phenomenological constraints based upon existing data. Unlike previous meson cloud model calculations, which accounted for kaon loop contributions with on-shell intermediate states alone, this work includes off-shell terms and contact interactions, which impact the shape of the $s-\bar{s}$ difference. We identify a valence-like component of $s(x)$ which is balanced by a $\delta$-function contribution to $\bar{s}(x)$ at $x=0$, so that the integrals of $s$ and $\bar{s}$ over the experimentally accessible region $x>0$ are not equal. Using a regularization procedure that preserves chiral symmetry and Lorentz invariance, we find that existing data limit the integrated value of the second moment of the asymmetry to the range $-0.07\times 10^{-3}\le ⟨x(s-\bar{s})⟩\le 1.12\times 10^{-3}$ at a scale of $Q^2=1$GeV${}^2$. This is too small to account for the NuTeV anomaly and of the wrong sign to enhance it.

Comments: 5 pages, 4 figures