Unitarisation of EFT Amplitudes for Dark Matter Searches at the LHC

Understand

We propose a new approach to the LHC dark matter search analysis within the effective field theory (EFT) framework by utilising the K-matrix unitarisation formalism.

• This approach provides a reasonable estimate of the dark matter production cross section at high energies, and hence allows reliable bounds to be placed on the cut-off scale of relevant operators without running into the problem of perturbative unitarity violation.
• We exemplify this procedure for the effective operator D5 in monojet dark matter searches in the collinear approximation.
• We compare our bounds to those obtained using the truncation method and identify a parameter region where the unitarisation prescription leads to more stringent bounds.