Vus and neutron beta decay

We discuss the effect of the recent change of $V_{\rm us}$ by three standard deviations on the standard model predictions for neutron beta decay observables. We also discuss the effect the experimental error bars of $V_{\rm us}$ have on such predictions. Refined precision tests of the standard model will be made by a combined effort to improve measurements in neutron beta decay and in strangeness-changing decays. By itself the former will yield very precise measurements of $V_{\rm ud}$ and make also very precise predictions for $V_{\rm us}$

Effective operator contributions to the oblique parameters

We present a model and process independent study of the contributions from non-Standard Model physics to the oblique parameters S, T and U. We show that within an effective lagrangian parameterization the expressions for the oblique parameters in terms of observables are consistent, while those in terms of the vector-boson vacuum polarization tensors are ambiguous. We obtain the constraints on the scale of new physics derived from current data on S, T and U and note that deviations in U from its Standard Model value would favor a scenario where the underlying physics does not decouple.Comment: 13 pages, RevTe

Sea Contributions to Spin 1/2 Baryon Structure, Magnetic Moments, and Spin Distribution

We treat the baryon as a composite system made out of a \lq\lq core" of three quarks (as in the standard quark model) surrounded by a \lq\lq sea" (of gluons and $q\bar{q}$-pairs) which is specified by its total quantum numbers like flavor, spin and color. Specifically, we assume the sea to be a flavor octet with spin 0 or 1 but no color. The general wavefunction for spin 1/2 baryons with such a sea component is given. Application to the magnetic moments is considered. Numerical analysis shows that a scalar (spin 0) sea with an admixture of a vector (spin 1) sea can provide very good fits to the magnetic moment data {\em using experimental errors}. Our best fit automatically gives $g_A/g_V$ for neutron beta decay in agreement with data. This fit also gives reasonable values for the spin distributions of the proton and neutron.Comment: 24 pages, REVTEX. References modifie

A priori mixed hadrons, hyperon non-leptonic decays, and the |\Delta I|=1/2 rule

The |\Delta I|=1/2 rule in non-leptonic decays of hyperons can be naturally understood by postulating a priori mixed physical hadrons, along with the isospin invariance of the responsible transition operator. It is shown that this operator can be identified with the strong interaction Yukawa hamiltonian.Comment: Workshops on Particles and Fields and Phenomenology of Fundamental Interactions. J. C. D'Olivo, A. Fernandez, and M. A. Perez, Ed