Two-boson exchange corrections to parity-violating elastic electron-proton scattering

Details of the calculation of two-boson exchange effects in parity-violating elastic ep scattering within a simple hadronic model, including both the nucleon and the Delta(1232)-resonance intermediate states, are presented. We examine the sensitivity of our results with respect to choice of form factors. We emphasize the importance of using correct relations relating N -> Delta and Delta -> N transition vertex functions. The N Delta Coulomb quadrupole transition is found to play an important role at higher Q(2) >= 3.0 GeV2. We also elucidate the relation between our results and the well-known result on the gamma Z-boson exchange effect given by Marciano and Sirlin. The effect of the nucleon contribution delta(N) to parity asymmetry A(PV) is found to be, in general, larger than the corresponding Delta contribution delta(Delta) except at extreme forward angles. Corrections to the extracted values of the strange form factors G(E)(s) + beta G(M)(s) from the HAPPEX, A4, and G0 data are also presented. The total TBE corrections to the extracted values of G(E)(s) + beta G(M)(s) in recent HAPPEX, G0, and A4 experiments are, depending on kinematics, found to be small except in a few cases where they range from -20.6% to 48.3%.