Current bounds on the type-Z <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>Z</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:math> three-Higgs-doublet model
Rafael Boto, Jorge C. Romão, João P. Silva
Abstract
Type-Z models, where charged leptons, up type quarks, and down type quarks each couple to a different scalar, are only possible when there are three or more Higgs doublets. We consider the type-Z three-Higgs-doublet model imposed by a softly broken ${\mathbb{Z}}_{3}$ symmetry. We take into account all theoretical and experimental constraints, including perturbative unitarity and bounded from below conditions that we develop here. Since there can be cancellations between the two charged Higgs in $B\ensuremath{\rightarrow}{X}_{s}\ensuremath{\gamma}$ (and in $h\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma}$), the lower bounds obtained on the charged Higgs masses are alleviated. We find regions of parameter space where both charged scalars can be relatively light. We also discuss in detail the important physical differences between exact alignment and approximate alignment, and present some useful benchmark points.