Chargino mass and Rb anomaly Original Research Article

We reexamine the possible magnitude of the supersymmetric contribution to Rb with imposed all available phenomenological constraints and demanding good quality of the global fit to the precision electroweak data. For low tan β in the region of the parameter space with M2 ≈ |μ| and ,μ < 0 a shift in Rb remains significant (δRb ≈ 0.002) even for the lighter chargino as heavy as 90-1000eV It is an interesting mixture of the up-higgsino and gaugino. The rôle of various phenomenological constraints is discussed in analytic form and importance of small but nonnegligible left-right mixing in the stop sector is emphasized in this context. Since the available data do not rule out the large tan β scenario, this option for enhancement of Rb is also reviewed.