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[en] We study the evolution of R-parity-violating (RPV) couplings in the minimum supersymmetric standard model, between the electroweak and grand unification scales, assuming a family hierarchy for these coupling strengths. Particular attention is given to solutions where both the R-conserving and R-violating top-quark Yukawa couplings simultaneously approach infrared fixed points; these we analyze both algebraically and with numerical solutions of the evolution equations at the one-loop level. We identify constraints on these couplings at the GUT scale, arising from lower limits on the top-quark mass. We show that fixed points offer a new source of bounds on RPV couplings at the electroweak scale. We derive evolution equations for the CKM matrix, and show that RPV couplings affect the scaling of the unitarity triangle. The fixed-point behavior is compatible with all present experimental constraints. However, fixed-point values of RPV top-quark couplings would require the corresponding sleptons or squarks to have a mass approx-gt m_t to suppress strong new top-quark decays to sparticles. copyright 1996 The American Physical Society

[en] Within the minimal supersymmetric standard model we study the three body decay of the lighter top squark t₁→bWχ₁⁰ and compare this decay with the flavor-changing two body decay t₁→cχ₁⁰. Here χ₁⁰ is the lightest neutralino which we assume to be the lightest supersymmetric particle. We do this for scenarios where two body decays at the tree level are forbidden for the light top squark. We give the complete analysis for the three body decay and compare it with the mentioned two body decay. We discuss our numerical results in view of the upgraded Fermilab Tevatron, the CERN LHC, and a 500 GeV e⁺e^- Linear Collider. copyright 1997 The American Physical Society

[en] We study the evolution of R-parity-violating (RPV) couplings in the minimum supersymmetric standard model, between the electroweak and grand unification scales, assuming a family hierarchy for these coupling strengths. Particular attention is given to solutions where both the R-conserving and R-violating top quark Yukawa couplings simultaneously approach infrared fixed points; these we analyse both algebraically and with numerical solutions of the evolution equations at one-loop level. We identify constraints on these couplings at the GUT scale, arising from lower limits on the top quark mass. We show that fixed points offer a new source of bounds on RPV couplings at the electroweak scale. We derive evolution equations for the CKM matrix, and show that RPV couplings affect the scaling of the unitarity triangle. The fixed-point behaviour is compatible with all present experimental constraints. However, fixed-point values of RPV top-quark couplings would require the corresponding sleptons or squarks to have mass ≥ m_t to suppress strong new top decays to sparticles. (author)

[en] The occurrence of fixed points in the renormalization group evolution of R-parity-violating (RPV) couplings in the minimum supersymmetric standard model (MSSM) is quantified, assuming that third generation couplings are dominant. These fixed points give new upper bounds on the RPV couplings at the electroweak scale. To avoid unacceptable top-quark decays the final-state sparticles participating in these RPV decays must have masses >or∼m_t. We also discuss possible RPV signals at the upgraded LEP collider from pair production and decay of the lightest sparticle (expected to be the lightest neutralino but possibly a sneutrino). (orig.)