Phenomenological indications of the scale of supersymmetry

Electroweak precision measurements can provide indirect information about the possible scale of supersymmetry already at the present level of accuracy. We update the present-day sensitivities of precision data using m_t = 172.7±2.9 GeV for the experimental value of the top-quark mass, within the constrained minimal supersymmetric extension of the Standard Model (CMSSM), in which there are three independent soft supersymmetry-breaking parameters m_1/2, m₀ and A₀. In addition to M_W and sin²θ_eff, the analysis is based on (g−2)_μ, BR(b→sγ) and the lightest MSSM Higgs boson mass, M_h. Assuming initially that the lightest supersymmetric particle (LSP) is a neutralino, we display the CMSSM results as functions of m_1/2, fixing m₀ so as to obtain the cold dark matter density allowed by WMAP and other cosmological data for specific values of A₀, tan β and μ>0. For a sample value of tan β we analyze how the global χ² function would change following a possible future evolution of the experimental central value of m_t and its error. In a second step, we extend the analysis to other constrained versions of the MSSM: the NUHM in which the soft supersymmetry-breaking contributions to the Higgs masses are independent and the Higgs mixing parameter μ and the pseudoscalar Higgs mass M_A become additional free parameters compared to the CMSSM, a VCMSSM in which the bilinear soft supersymmetry breaking parameter B₀ = A₀ − m₀, and the GDM in which the LSP is the gravitino. In all scenarios we find indications for relatively light soft supersymmetry-breaking masses, offering good prospects for the LHC and the ILC, and in some cases also for the Tevatron.