The dark side of mSUGRA

We study the μ<0 branch of the minimal supergravity ansatz of the minimal supersymmetric standard model. The extent to which μ<0 is disfavoured compared to μ>0 in global fits is calculated with Markov Chain Monte Carlo methods and bridge sampling. The fits include state-of-the-art two-loop MSSM contributions to the electroweak observables MW and sin 2θwl, as well as the anomalous magnetic moment of the muon (g-2)μ, the relic density of dark matter and other relevant indirect observables. μ<0 is only marginally disfavoured in global fits and should be considered in mSUGRA analyses. We estimate that the ratio of probabilities is P(μ<0)/P(μ>0) = 0.07-0.16