SUPERSYMMETRIC FLAVOR-CHANGING NEUTRAL CURRENTS - EXACT AMPLITUDES AND PHENOMENOLOGICAL ANALYSIS

We present an exact calculation of the most general supersymmetric amplitudes for K0-K0BAR and B0-B0BAR mixing resulting from gluino box diagrams. We use these amplitudes to place general constraints on the magnitude of off-generational, flavor-changing mass mixings in the squark mass matrices (with arbitrary chirality structures) that can arise both in and beyond the minimal supersymmetric Standard Model (MSSM). We use the renormalization-group equations to estimate these mass mixings in the MSSM and in nonminimal supersymmetric models in terms of a general parameterization of universal soft supersymmetry breaking. We show that while these mass mixings are too small in the MSSM to yield any observable effects, the converse is true in most nontrivial extensions of the MSSM, including supersymmetric GUTs. In nonminimal supersymmetry, the K(L)-K(S) mass difference is sensitive to such contributions from supersymmetric particles with masses up to 100 TeV (10 TeV for the B(L)-B(S) mass difference), and the CP impurity parameter epsilon(K) is sensitive to sparticle masses up to 1000 TeV. We show that supersymmetric CP violation can be predominantly ''superweak'' (i.e., contribute mainly to epsilon(K)) or ''milliweak'' (epsilon') depending on the chirality of the off-generational squark mass mixings. The rare decay b --> sgamma is less sensitive than the aforementioned constraints, but probes somewhat different squark mass mixings. The lepton-number violating decay mu --> egamma is very sensitive to off-generational slepton mixing for sleptons up to a TeV. All these processes provide valuable information regarding the structure of physics beyond the MSSM pertaining to arbitrarily high mass scales, including the nature of supersymmetry breaking.