Hadronic production and decays of charginos and neutralinos in split supersymmetry

In the scenario recently proposed by Arkani-Hamed and Dimopoulos, the supersymmetric scalar particles are all very heavy, at least of the order of ${10}^9\mathrm{GeV}$ but the gauginos, Higgsino, and one of the $CP$-even neutral Higgs bosons remain light under a TeV. In addition to gluino production, the first SUSY signature would be pair production of neutralinos and/or charginos. Here we study, with explicit $CP$ violation, the production of neutralinos and charginos at hadronic colliders as well as the possible decay modes. We notice that the branching ratio of the neutralino radiative decay can be sizable unlike the case with light sfermions. In particular, the decay of ${\tilde{\chi }}_3^0\to {\tilde{\chi }}_1^0\gamma$ has a branching ratio of the order $O(1)$ percent. In colliders, it would give rise to signatures of an isolated single photon plus missing energy.