Theory Colloquium

Bounds on New Physics from Parity Violation in Atomic Cesium

by Roberto CASALBUONI (INFN, Florence)

TH Auditorium (CERN)

TH Auditorium


Assuming the latest experimental determination of the weak charge of atomic cesium we analyze its implications for possible new physics. We notice that the data would imply positive upper and lower bounds on the new physics contribution to the weak charge, dNQW. The required new physics should be of a type not severely constrained by the high energy precision data. A simplest possibility would be new neutral vector bosons almost unmixed to the Z and with sizeable couplings to fermions. The lower positive bound would however forbid zero or negative dNQW and exclude not only the standard model but also models with sequential Z’in particular simple-minded towers of Z-like excitations from extra-dimensions. The bound would also imply an upper limit on the Z’ mass within the models allowed. Conclusions are also derived for models of four-fermion contact interactions.