AION/Magis

Abstract:

We propose a general scheme for constructing models in which the Standard Model (SM) gauge interactions are the mediators of supersymmetry breaking to the fields in the supersymmetric SM, but where the SM gauge groups couple directly to the sector which breaks supersymmetry dynamically. Despite the direct coupling, the models preserve perturbative unification of the SM gauge coupling constants. Furthermore, the supergravity contributions to the squark and slepton masses can be naturally small, typically being much less than 1% of the gauge-mediated (GM) contributions. Both of these goals can be achieved without need of a fine-tuning or a very small coupling constant. This scheme requires run-away directions at the renormalizable level which are only lifted by non-renormalizable terms in the superpotential. To study the proposed scheme in practice, we develop a modified class of models based on SU(N) x SU(N - 1) which allows us to gauge an SU(N - 2) global symmetry. However, we point out a new problem which can exist in models where the dynamical supersymmetry breaking sector and the ordinary sector are directly coupled - the two-loop renormalization group has contributions which can induce negative (mass)(2) for the squarks and sleptons. We clarify the origin of the problem and argue that it is likely to be surmountable. We give a recipe for a successful model. (C) 1998 Published by Elsevier Science B.V.

Abstract:

The lifetimes of the B- and B̄0 mesons are measured using the partially reconstructed semileptonic decays B̄ → Dl- v̄X, where D0 is either a D0 or D*+ meson. The data were collected by the CDF detector at the Fermilab Tevatron collider during 1992-1995 and correspond to about 110 pb-1 of pp collisions at √s = 1.8 TeV. We measure decay lengths and extract the lifetimes to be τ(B-) = 1.637±0.058-0.043+0.045 ps and τ(B̄0) = 1.474±0.039-0.051+0.052 ps, and the ratio of the lifetimes to be τ(B-)/τ(B̄0) = 1.110±0.056-0.030+0.033, where the first uncertainties are statistical and the second are systematic.