Indirect Sensitivities to the Scale of Supersymmetry

Precision measurements, now and at a future linear electron-positron collider (ILC), can provide indirect information about the possible scale of supersymmetry. We illustrate the present-day and possible future ILC sensitivities within the constrained minimal supersymmetric extension of the Standard Model (CMSSM), in which there are three independent soft supersymmetry-breaking parameters m1/2, m0 and A0. We analyze the present and future sensitivities separately for MW , sin 2 θeff , (g − 2)μ, BR(b → sγ), BR(Bs → μμ), Mh and Higgs branching ratios. We display the observables as functions of m1/2, 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. In a second step, we investigate the combined sensitivity of the currently available precision observables, MW , sin 2 θeff , (g − 2)μ and BR(b → sγ), by performing a χ analysis. The current data are in very good agreement with the CMSSM prediction for tan β = 10, with a clear preference for relatively small values of m1/2 ∼ 300 GeV. In this case, there would be good prospects for observing supersymmetry directly at both the LHC and the ILC, and some chance already at the Tevatron collider. For tan β = 50, the quality of the fit is worse, and somewhat larger m1/2 values are favoured. With the prospective ILC accuracies the sensitivity to indirect effects of supersymmetry greatly improves. This may provide indirect access to supersymmetry even at scales beyond the direct reach of the LHC or the ILC. CERN–PH–TH/2004-220 November 2004