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Unformatted text preview: PHY5667 Take-Home Final Exam [Due at Noon on Tue, Dec 7] * Work alone. You can look up books, but do not discuss with anyone . * Exams will be collected at my office (511 Keen) between 11am and 12pm on Tue, Dec 7. * Questions are not allowed except for clarifying the meanings of the problems. (1) Consider the following QFT — called “quantum electrodynamics (QED)” — for a massive Dirac spinor (“electron”) ψ and a massless vector (“photon”) A μ with the interaction given by L int = eA μ ψγ μ ψ , where e is a real constant. Use m for the electron mass. (i) Consider the production of an electron-positron pair from a photon pair, i.e., A ( k 1 ,s 1 )+ A ( k 2 ,s 2 ) → ψ ( p 1 ,s 1 ) + ψ ( p 2 ,s 2 ). (a) Draw Feynman diagrams for this process at the second order in perturbation theory. Be sure to draw all necessary arrows, both for charge and momentum. (b) Write down the corresponding amplitude i M fi ....
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- Fall '10