Phenomenological analysis of a topless left-right model

Abstract

We reanalyze a topless left-right model due to Ma, after allowing flavor-changing neutral currents which are consistent with all the experimental limits coming from flavor-changing processes. The resulting model can naturally reproduce the observed values of B_d⁰-B̅_d⁰ mixing, where the original model had failed by 8 orders of magnitude. Thus, the model is viable from the viewpoint of low-energy phenomenology. In the case of Z⁰ physics, however, we see that the model makes distinctive predictions for some of the Z⁰→ff̅ partial widths due to the nonstandard couplings of the fermion f. The recent measurements of these partial widths from CERN LEP seem to clearly rule out this model. Indeed the precision measurement of the Z⁰→bb̅ partial width along with the known properties of b decay seems to rule out any topless model.