Two photon exchange amplitude with π N intermediate states: spin-1/2 and spin-3/2 channels
Abstract
We calculate two-photon exchange (TPE) amplitudes for the elastic electron-proton scattering, and take into account intermediate hadronic states containing π N system with total angular momentum 1/2 or 3/2, which includes 8 different channels. This is the improvement of our previous calculation, where only the π N states with quantum numbers of (1232) resonance were included. The results show good consistency with recent experimental data. At high Q2, newly-calculated contributions affect the correction to the measured proton form factor ratio μ GE/GM. The total correction becomes somewhat smaller compared to our previous work, but is still significant and grows approximately linearly with Q2. Comparing contributions of different channels, we found that larger contributions come from the channels with quantum numbers of lightest resonances.
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