Constraints on the s−s¯ asymmetry of the proton in chiral effective theory

Abstract We compute the s − 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 − s ¯ difference. We identify a valence-like component of s ( x ) which is balanced by a δ -function contribution to s ¯ ( x ) at x = 0 , so that the integrals of s and 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 × 10 − 3 ≤ 〈 x ( s − s ¯ ) 〉 ≤ 1.12 × 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.