Tau-odd correlation on the Z0-Peak

T-odd observables can be due either to T-violation or to unitarity corrections. We find a non-vanishing expectation value of a T-odd operator for from one-loop electroweak corrections to the resonant decay and from interference with the background. For unpolarized beams, chirality conservation allows only one relevant absorptive part of the interference between different amplitudes. We identify this unique T-odd effect as the spin correlation , where are the transverse (within the production plane) and normal (to the plane) spin components for f and , respectively. In the standard theory it is generated from the Z, W exchanges in the final vertex, from the Z-γ self-energy and from the tree-…

Present and future bounds on nonstandard neutrino interactions

We consider Non-Standard neutrino Interactions (NSI), described by four-fermion operators of the form ((nu) over bar (alpha)gammanu(beta)) ((f) over bar gammaf), where f is an electron or first generation quark. We assume these operators are generated at dimension greater than or equal to 8, so the related vertices involving charged leptons, obtained by an SU(2) transformation nu(delta)-->e(delta), do not appear at tree level. These related vertices necessarily arise at one loop, via W exchange. We catalogue current constraints from sin(2)theta(W) measurements in neutrino scattering, from atmospheric neutrino observations, from LEP, and from bounds on the related charged lepton operators. W…

Análisis de la polarización del ? y correlaciones de espín a las energías de LEP