A two-Higgs-doublet Model Free of Flavor-Changing Neutral Currents Naturally at Tree-Level Chilong Lin ^{1*}^{1}National Museum of Natural Science, Taichung, Taiwan^{2}Exhibition Department, National Museum of Natural Science, Taichung, Taiwan* Presenter:Chilong Lin, email:lingo@mail.nmns.edu.tw A new type of two-Higgs-doublet model (2HDM) free of flavor-changing neutral currents (FCNCs) naturally at tree-level is to be presented in this article.
Unlike previous natural-flavor-conserving (NFC) models, such a model allows both Higgs doublets to couple with a same fermion simultaneously. Both components of its quark mass matrices corresponding to different Higgs doublets are non-vanish and can be diagonalized by a same unitary transformation. That means the problem of NFCNs at tree-level does not exist in such a model. The general pattern of such FCNC-free matrix pairs is derived without any assumptions or symmetries except the hermiticity of the mass matrices. That assumption gives a FCNC-free condition which reduces the number of parameters in the mass matrices down to a manageable level. Thus, eigenvalues and eigenvectors are analytically derived and found to be very simple. The unitary transformation matrix for each fermion type depends only on two parameters. It looks much more rational than previous similar models. Keywords: 2HDM, FCNC, NFC |