Abstract
We examine extensions of the standard model (SM), basing our assumptions on what has already been observed; we do not consider anything fundamentally different, such as grand unification or supersymmetry, which is not directly suggested by the SM itself. We concentrate on the possibility of additional low mass fermions (relative to the Planck mass) and search for combinations of representations which do not produce any gauge anomalies. Generalizations of the SM weak hypercharge quantization rule are used to specify the weak hypercharge, modulo 2, for any given representation of the non-Abelian part of the gauge group. Strong experimental constraints are put on our models, by using the renormalization group equations to obtain upper limits on fermion masses and to check that there is no U(1) Landau pole below the Planck scale. Our most promising model contains a fourth generation of quarks without leptons and can soon be tested experimentally.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.