Collider signals from slow decays in supersymmetric models with an intermediate-scale solution to the mu problem - art. no. 095008

The problem of the origin of the mu parameter in the minimal supersymmetric standard model can be solved by introducing singlet supermultiplets with n on-renormalizable couplings to the ordinary Higgs supermultiplets. The Pecc ei-Quinn symmetry is broken at a scale which is the geometric mean between the weak scale and the Planck scale, yielding a mu term of the right order of magnitude and an invisible axion. These models also predict one or more singlet fermions which have electroweak-scale masses and suppressed couplin gs to MSSM states. I consider the case that such a singlet fermion, contain ing the axino as an admixture, is the lightest supersymmetric particle. I w ork out the relevant couplings in several of the simplest models of this ty pe, and compute the partial decay widths of the next-to-lightest supersymme tric particle involving leptons or jets. Although these decays will have an average proper decay length which is most likely much larger than a typica l collider detector, they can occasionally occur within the detector, provi ding a striking signal. With a large sample of supersymmetric events, there will be an opportunity to observe these decays, and so gain direct informa tion about physics at very high energy scales.