Chiral corrections to hyperon vector form factors.

We show that the leading SU(3)-breaking corrections to the ∆S = 1 f1 vector form factors of hyperons are O(ms) and O(m 3/2 s ), and are expected to be ∼ 20–30% by dimensional analysis. This is consistent with the Ademollo–Gatto theorem, in a sense that we explain. We compute the O(ms) corrections and a subset of the O(m 3/2 s ) corrections using an effective lagrangian in which the baryons are treated as heavy particles. All of these corrections are surprisingly small, ∼ 5%; combining them, we obtain ∼ 5–10% corrections. The pattern of corrections is very different than that predicted by quark models. PACS 13.31.Ce, 14.20.Gk, 14.20.Jn This work was supported by the Director, Office of Energy Research, Office of High Energy and Nuclear Physics, Division of High Energy Physics of the U.S. Department of Energy under Contract DE-AC03-76SF00098.