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There are already antiproton proton pairs experimentally created at LEP , Proton–antiproton pair production in two-photon collisions at LEP The reaction is studied with the L3 detector at LEP. The analysis is based on data collected at e+e− center-of-mass energies from 183 GeV to 209 GeV, corresponding to an integrated luminosity of 667 pb^−1. The ...


The reaction $$ \gamma\to e^+ e^-$$ is actually forbidden on kinematic grounds - one can show that momentum and energy cannot be simultaneously conserved if there is not something else to take "excess" momentum, e.g. a heavy nucleus nearby - pair production from gamma rays happens in metals, for example, but not in vacuum. Of course, given enough energy, it ...

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