We report on a chiral effective field theory calculation of Compton
scattering from the proton. Our calculation includes pions, nucleons, and the
Delta(1232) as explicit degrees of freedom. It uses the "delta expansion", and
so implements the hierarchy of scales m_pi < M_Delta-M_N < Lambda_chi. In this
expansion the power counting in the vicinity of the Delta peak changes, and
resummation of the loop graphs associated with the Delta width is indicated.
We have computed the nucleon Compton amplitude in the delta expansion up to
N3LO for photon energies of the order of m_pi. This is the first order at which
the proton Compton scattering amplitudes receive contributions from contact
operators which encode contributions to the spin-independent polarisabilities
from states with energies of the order of Lambda_chi. We fit the coefficients
of these two operators to the experimental proton Compton data that has been
taken in the relevant photon-energy domain, and are in a position to extract
new results for the proton polarisabilities alpha and beta.Comment: 6 pages. Proceeding of Sixth International Workshop on Chiral
Dynamics, Bern (Switzerland), 6th -- 10th July 2009. To be published in Po