R-parity-breaking SUSY solution to the Rb and ALEPH anomalies.

We discuss an optimal R-parity breaking SUSY solution to the Rb excess as well as the ALEPH 4-jet anomaly. The latter arises from the pair production of stop via chargino decay at LEP1.5, followed by its R–violating decay into a light quark pair. The model satisfies top quark and Z–boson decay constraints along with gaugino mass unification. CERN-TH/96-203 August, 1996 [email protected] [email protected] Two of the intriguing results from LEP which have attracted a good deal of theoretical interest are the Rb and the ALEPH 4-jet anomalies. The first anomaly refers to the LEP1 value of Rb(≡ Γ Z /Γ Z ) being ∼ 2σ larger than the SM prediction [1, 2]. The second refers to the anomalous 4-jet events recently reported [3] by the ALEPH experiment at LEP1.5, each of which seems to consist of dijet pairs with a common invariant mass ∼ 55 GeV. It is now widely recognized [4, 5, 6] that the minimal supersymmetric standard model (MSSM) offers a viable solution to the Rb anomaly in the low tan β region if one assumes a relatively light top squark (t̃1) and chargino (χ̃1). The assumption of a R–parity violating Yukawa interaction term would invalidate the canonical missing ET (ET / ) signature for superparticle production and thus the LEP1.5 limit on chargino mass [7],