Bhabha scattering is the process electron plus

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Bhabha scattering is the process electron plus positron goes to electron plus positron. Note that the photon carries no electric charge; this is a neutral current interaction. time
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Feynman Diagrams photon Electron-electron repulsion. The EM force is mediated through a photon! From a distance, this looks like the electrons are repelling each other. However, the Feynman diagram shows that an electron emits a photon and is pushed back to conserve momentum. The second electron also changed direction since it absorbed the photon. - e - e - e - e
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January 16, 2001 Physics 841 10 Adding Amplitudes = Note that an electron going backward in time is equivalent to an electron going forward in time. M = Transition amplitudes (matrix elements) must be summed over indistinguishable initial and final states. exchange annihilation +
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January 16, 2001 Physics 841 11 More First Order QED Essentially the same Feynman diagram describes the amplitudes for related processes, as indicated by these three examples. The first amplitude describes electron positron annihilation producing two photons. The second amplitude is the exact inverse, two photon production of an electron positron pair. The third amplitude represents in the lowest order amplitude for Compton scattering in which a photon scatters from and electron producing a photon and an electron in the final state.
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January 16, 2001 Physics 841 12 Higher Order Contributions Just as we have second order perturbation theory in non-relativistic quantum mechanics, we have second order perturbation theory in quantum field theories.
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