Weak properties of theτlepton via a spin-0 unparticle

Abstract

We consider a spin-0 unparticle and calculate its contribution to the weak properties of a fermion, which in the proper limit reduce to previously reported results for the electromagnetic properties. We then obtain an estimate for the electromagnetic and weak properties of the $\ensuremath{\tau}$ lepton. For the unparticle parameters, we consider the most recent bounds from the lepton flavor-violating decay $\ensuremath{\tau}\ensuremath{\rightarrow}3\ensuremath{\mu}$, the muon anomalous magnetic moment, and the data for monojet production plus missing transverse energy at the LHC. In the most promising scenario, it is found that the unparticle contributions to the $\ensuremath{\tau}$ electromagnetic properties can be larger than the contributions predicted by the standard model and some of its extensions, such as the seesaw model and extensions of the minimal supersymmetric standard model with a mirror fourth generation and vectorlike multiplets. As for the contributions to the weak properties, they are larger than the standard model contributions but are much smaller than the current experimental limits. We also discuss the case of the electromagnetic and weak properties of the bottom and top quarks.