Two-loop mass splittings in electroweak multiplets: winos and minimal dark matter

TL;DR

This paper presents precise two-loop calculations of mass splittings in electroweak multiplets, including winos and minimal dark matter quintuplets, impacting collider phenomenology and dark matter constraints.

Contribution

It provides the first two-loop mass splitting calculation for an electroweak fermionic quintuplet and improves previous results with consistent renormalisation and finite quark mass effects.

Findings

Two-loop corrections can alter particle lifetimes by up to 40%.

Mass splittings in the MDM quintuplet vary with mass, influenced by heavy fermion loops.

Enhanced precision constrains the lifetimes of charged fermions in dark matter models.

Abstract

The radiatively-induced splitting of masses in electroweak multiplets is relevant for both collider phenomenology and dark matter. Precision two-loop corrections of $\mathcal{O}$(MeV) to the triplet mass splitting in the wino limit of the minimal supersymmetric standard model can affect particle lifetimes by up to $40\%$. We improve on previous two-loop self-energy calculations for the wino model by obtaining consistent input parameters to the calculation via two-loop renormalisation-group running, and including the effect of finite light quark masses. We also present the first two-loop calculation of the mass splitting in an electroweak fermionic quintuplet, corresponding to the viable form of minimal dark matter (MDM). We place significant constraints on the lifetimes of the charged and doubly-charged fermions in this model. We find that the two-loop mass splittings in the MDM quintuplet are not constant in the large-mass limit, as might naively be expected from the triplet calculation. This is due to the influence of the additional heavy fermions in loop corrections to the gauge boson propagators.