What if supersymmetry breaking unifies beyond the GUT scale?
TH Division, PH Department, CERN, 1211, Geneva 23, Switzerland
2 William I. Fine Theoretical Physics Institute, University of Minnesota, Minneapolis, MN, 55455, USA
Revised: 17 May 2010
Published online: 9 July 2010
We study models in which soft supersymmetry-breaking parameters of the MSSM become universal at some unification scale, M in, above the GUT scale, M GUT. We assume that the scalar masses and gaugino masses have common values, m 0 and m 1/2 respectively, at M in. We use the renormalisation-group equations of the minimal supersymmetric SU(5) GUT to evaluate their evolutions down to M GUT, studying their dependences on the unknown parameters of the SU(5) superpotential. After displaying some generic examples of the evolutions of the soft supersymmetry-breaking parameters, we discuss the effects on physical sparticle masses in some specific examples. We note, for example, that near-degeneracy between the lightest neutralino and the lighter stau is progressively disfavoured as M in increases. This has the consequence, as we show in (m 1/2,m 0) planes for several different values of tan β, that the stau-coannihilation region shrinks as M in increases, and we delineate the regions of the (M in,tan β) plane where it is absent altogether. Moreover, as M in increases, the focus-point region recedes to larger values of m 0 for any fixed tan β and m 1/2. We conclude that the regions of the (m 1/2,m 0) plane that are commonly favoured in phenomenological analyses tend to disappear at large M in.
© Springer-Verlag / Società Italiana di Fisica, 2010