Decades of precision measurements have firmly established the Kobayashi-Maskawa phase as the dominant source of the charge-parity ($CP$) violation observed in weak quark decays. However, it is still unclear whether $CP$ violation is explicitly encoded in complex Yukawa matrices or instead stems from spontaneous symmetry breaking with underlying $CP$-conserving Yukawa and Higgs sectors. Here we study the latter possibility for the case of a generic two-Higgs-doublet model. We find that theoretical constraints limit the ratio $t_{\beta }$ of the vacuum expectation values (vevs) to the range $0.22\le t_{\beta }\le 4.5$ and imply the upper bounds $M_{H^{\pm }}\le 435\mathrm{GeV}$, $M_{H_2^0}\le 485\mathrm{GeV}$ and $M_{H_3^0}\le 545\mathrm{GeV}$ for the charged and extra neutral Higgs masses. We derive lower bounds on charged-Higgs couplings to bottom quarks which provide a strong motivation to study the nonstandard production and decay signatures $pp\to qb{H}^{\pm }(\to q^{\prime }b)$ with all flavors $q,q^{\prime }=u$, $c$, $t$ in the search for the charged Higgs boson. We further present a few benchmark scenarios with interesting discovery potential in collider analyses.

• Received 8 January 2020
• Accepted 19 June 2020

DOI:https://doi.org/10.1103/PhysRevLett.125.031801

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

Published by the American Physical Society