Tuesday, March 6, 2012

1203.0254 (Andre Walker-Loud et al.)

The Electromagnetic Self-Energy Contribution to M_p - M_n and the
Isovector Nucleon Magnetic Polarizability
   [PDF]

Andre Walker-Loud, Carl E. Carlson, Gerald A. Miller
We update the determination of the isovector nucleon electromagnetic self-energy, valid to leading order in QED. A technical oversight in the literature concerning the elastic contribution to Cottingham's formula is corrected and modern knowledge of the structure functions is used to precisely determine the inelastic contribution. We find \delta M_{p-n}^\gamma = 1.30(03)(47) MeV. The largest uncertainty arises from a subtraction term required in the dispersive analysis, which can be related to the isovector magnetic polarizability. With plausible model assumptions, we can combine our calculation with additional input for lattice QCD to constrain this polarizability as: \beta_{p-n} = -0.87(85) x 10^{-4} fm^3.
View original: http://arxiv.org/abs/1203.0254

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