1993/06/09 by J. Bernabéu, J. Bernabeu, E. Nardi +3 · 2 citations
Physics and Astronomy · #Dark Matter and Cosmic Phenomena #Neutrino Physics Research #Particle physics theoretical and experimental studies #hep-ph
paper · pdf · doi:10.1016/0550-3213(93)90446-v
published as Nucl.Phys.B409:69-86,1993 · Plain Tex, 24 pages, + 2 PostScript figure appended after \bye (and available upon request), UM-TH 93--08, FTUV 93-14
arxiv created 1993/06/09 · openalex publication_date 1993/11/01 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
Together with the existence of new neutral gauge bosons, models based on extended gauge groups (rank > 4) often predict also new charged fermions. A mixing of the known fermions with new states with \it exotic weak-isospin assignments (left-handed singlets and right-handed doublets) will induce tree level flavour changing neutral interactions mediated by Z exchange, while if the mixing is only with new states with \it ordinary weak-isospin assignments, the flavour changing neutral currents are mainly due to the exchange of the lightest new neutral gauge boson Z^′. We show that the present experimental limits on μ-e conversion in nuclei give a nuclear-model-independent bound on the Z-e-μ vertex which is twice as strong as that obtained from μ→ e e e. In the case of E6 models these limits provide quite stringent constraints on the Z^′ mass and on the Z-Z^′ mixing angle. We point out that the proposed experiments to search for μ-e conversion in nuclei have good chances to find evidence of lepton flavour violation, either in the case that new exotic fermions are present at the electroweak scale, or if a new neutral gauge boson Z^′ of E6 origin lighter than a few TeV exists.