We present next-to-leading order predictions for the production of triphoton final states at the LHC and the Tevatron. Our results include the effect of photon fragmentation for the first time and we are able to quantify the impact of different isolation prescriptions. We find that calculations accounting for fragmentation effects at leading order, and those employing a smooth cone isolation where no fragmentation contribution is required, are in reasonable agreement with one another. However, larger differences in the predicted rates arise when higher order corrections to the fragmentation functions are included. In addition we present full analytic results for the $\gamma \gamma \gamma$ and $\gamma \gamma +\text{jet}$ one-loop amplitudes. These amplitudes, which are particularly compact, may be useful to future higher-order calculations. Our results are available in the Monte Carlo code mcfm.

• Received 20 March 2014

DOI:https://doi.org/10.1103/PhysRevD.89.113001