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arXiv · hep-ph/9810254

Isospin violation and the proton's neutral weak magnetic form factor

Randy Lewis·Nader Mobed
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Abstract

The effects of isospin violation on the neutral weak magnetic form factor of the proton are studied using two-flavour chiral perturbation theory. The first nonzero contributions appear at O(p^4) in the small-momentum expansion, and the O(p^5) corrections are also calculated. The leading contributions from an explicit Delta(1232) isomultiplet are included as well. At such a high order in the chiral expansion, one might have expected a large number of unknown parameters to contribute. However, it is found that no unknown parameters can appear within loop diagrams, and a single tree-level counterterm at O(p^4) is sufficient to absorb all divergences. The momentum dependence of the neutral weak magnetic form factor is not affected by this counterterm.

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Randy Lewis, Nader Mobed. 1998-10-05. Isospin violation and the proton's neutral weak magnetic form factor. https://doi.org/10.1103/physrevd.59.073002

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