The quantum correlation Rb−Rc in the MSSM: more hints of supersymmetry?

We study the correlation of quantum effects on the ratios Rb and Rc within the framework of the MSSM. While in the SM the quantity Rb is in discrepancy with experiment at the 2σ level from below, and Rc differs from the experimental result at the 1.5σ level from above, the theoretical prediction for both observables could simultaneously improve in the MSSM, provided that tan β is large enough (tan β ∼ mtmb and there exists a light supersymmetric pseudoscalar Higgs, and also a light chargino and a light stop, all of them in the 50 GeV ballpark. In view of the masses predicted for these SUSY particles, persistence of the “Rb−Rc crisis” in the next run of experiments would not only suggest indirect evidence of SUSY, but should also encourage direct finding of SUSY at LEP 200. We also point out the consistency of this picture with other observables and the intriguing possibility that this Z-physics scenario might allow getting a hint of SUSY at Tevatron through the simple observation of t → H+b.