Degenerate gaugino mass region and mono-boson collider signatures

In this paper we discuss search strategies at the LHC for light electroweak gauginos which are mostly Wino-like, Higgsino-like or an admixture. These states are typically degenerate with decay products that are less energetic and hence difficult to detect. In addition, their production cross-sections at a hadron collider are suppressed compared to colored states such as the gluinos. In order to detect these states one needs to trigger on initial or final state radiation. Many previous analyses have focussed on mono-jet and mono-photon triggers. In the paper we argue and show that these triggers are unlikely to succeed, due to the large background from QCD backgrounds for the mono-jet searches and the fact that the $p_T$ distribution of the mono-photons are rapidly decreasing functions of $p_T$. We show this with both an analytic calculation of photons in the initial state radiation and also a detailed numerical analysis. We then argue that mono-Z triggers, from Z decaying into charged leptons may well provide the best search strategy, in particular for Higgsino-like and mixed cases.