The LHC is not only the highest energy collider for protons and heavy ions, but also for photon photon and photon hadron ($\gamma$p and $\gamma$Pb) interactions. This is because the protons and ions accelerated in the LHC carry an electromagnetic field, which can be viewed as a source of photons, and such photons can interact with either other photons or with hadrons... (read more)
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