2015/12/31 by James M. Cline
Physics and Astronomy · #Dark Matter and Cosmic Phenomena #Electron #Higgs boson #Lepton #Nuclear physics #Particle Detector Development and Performance #Particle physics #Particle physics theoretical and experimental studies #Physics #Physics beyond the Standard Model #Quark #Two-Higgs-doublet model #Yukawa potential #hep-ph
paper · pdf · doi:10.1103/physrevd.93.075017
published as Phys. Rev. D 93, 075017 (2016) · 22 pages, 9 figures; v.2: added references; v.3: incorporated large tau Yukawa coupling into RGEs and in UV model; published version
arxiv created 2016/03/18 · openalex publication_date 2016/04/07 · arxiv updated 2016/04/13 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
There are indications of a possible breakdown of the standard model, suggesting that \ensuremathτ lepton interactions violate flavor universality, particularly through B meson decays. BABAR, Belle, and LHCb report high ratios of B\ensuremath→D(*)\ensuremathτ\ensuremathν. There are long-standing excesses in B\ensuremath→\ensuremathτ\ensuremathν and W\ensuremath→\ensuremathτ\ensuremathν decays and a deficit in inclusive \ensuremathτ to strange decays. We investigate whether two Higgs doublet models with the most general allowed couplings to quarks, and a large coupling to \ensuremathτ leptons, can explain these anomalies while respecting other flavor constraints and technical naturalness. Fits to B\ensuremath→D(*)\ensuremathτ\ensuremathν data require couplings of the new Higgs doublet to down-type quarks, opening the door to many highly constrained flavor-changing neutral current processes. We confront these challenges by introducing a novel ansatz that relates the new up- and down-type Yukawa couplings, and demonstrate viable values of the couplings that are free from fine-tuning. LEP and LHC searches for new Higgs bosons decaying via H0\ensuremath→\ensuremathτ+\ensuremathτ^\ensuremath- and H^\ifmmode±\else\textpm\fi\ensuremath→\ensuremathτ^\ifmmode±\else\textpm\fi\ensuremathν allow a window of masses mH=[100--125] GeV and m_\ifmmode±\else\textpm\fi\ensuremath∼100 GeV that is consistent with the predictions of our model. Contamination of the W+\ensuremath→\ensuremathτ+\ensuremathν signal by H+\ensuremath→\ensuremathτ+\ensuremathν decays at LEP could explain the apparent W\ensuremath→\ensuremathτ\ensuremathν excess. We predict that the branching ratio for Bs\ensuremath→\ensuremathτ+\ensuremathτ^\ensuremath- is not far below its current limit of several percent. An alternative model with decays of B\ensuremath→D(*)\ensuremathτ\ensuremathνs to a sterile neutrino is also argued to be viable.