41 research outputs found
Dynamical Structure of Baryons
Compton scattering offers a unique opportunity to study the dynamical
structure of hadrons over a wide kinematic range, with polarizabilities
characterizing the hadron active internal degrees of freedom. We present
calculations and detailed analysis of electric and magnetic and the
spin-dependent dynamical polarizabilities for the lowest in mass SU(3) octet of
baryons. These extensive calculations are made possible by the recent
implementation of semi-automatized calculations in chiral perturbation theory
which allows evaluating polarizabilities from Compton scattering up to
next-to-the-leading order. The dependencies for the range of photon energies
covering the majority of the meson photoproduction channels are analyzed.Comment: ICHEP2012, 6 page
Two Photon Exchange for Exclusive Pion Electroproduction
We perform detailed calculations of two-photon-exchange QED corrections to
the cross section of pion electroproduction. The results are obtained with and
without the soft-photon approximation; analytic expressions for the radiative
corrections are derived. The relative importance of the two-photon correction
is analyzed for the kinematics of several experiments at Jefferson Lab. A
significant, over 20%, effect due to two-photon exchange is predicted for the
backward angles of electron scattering at large transferred momenta
Radiative corrections and parity-violating electron-nucleon scattering
Radiative corrections to the parity-violating asymmetry measured in elastic
electron-proton scattering are analyzed in the framework of the Standard Model.
We include the complete set of one-loop contributions to one quark current
amplitudes. The contribution of soft photon emission to the asymmetry is also
calculated, giving final results free of infrared divergences. The one quark
radiative corrections, when combined with previous work on many quark effects
and recent SAMPLE experimental data, are used to place some new constraints on
electroweak form factors of the nucleon