ILC Phenomenology of the $Z_3$ symmetric Type-Z Three Higgs Doublet Model

Abstract

The Three-Higgs-Doublet Model (3HDM) extends the Standard Model by introducing two additional scalar doublets, leading to a rich spectrum of new particles: three neutral CP-even Higgs bosons ($h_1$, $H_2$, $H_3$), two neutral CP-odd Higgs bosons ($A_2$, $A_3$), and two charged Higgs bosons ($H_2^{+}$, $H_3^{+}$). In this work, we present a phenomenological study of the 3HDM at the future International Linear Collider (ILC) with a center-of-mass energy of $\sqrt{s}=1000\text{GeV}$. Applying a comprehensive set of theoretical and experimental constraints, we identify promising new physics signals with sufficiently large production cross-sections. Our analysis shows that $e^{+}{e}^{-}\to H_2{A}_2$, $e^{+}{e}^{-}\to H_2{H}_{2}Z$, $A_2{A}_{2}Z$, $H_2{H}_2^{\pm }{W}^{\mp }$, $A_2{H}_2^{\pm }{W}^{\mp }$ and $H_1{H}_2{A}_2$ are among the most sensitive channels to probe this extended Higgs sector. We demonstrate that a future ILC would offer a powerful platform to test these interactions and discover these heavier Higgs bosons thus providing evidence of physics beyond the Standard Model.

Comments: 16 pages, 4 figures, 22 tables (Version accepted for publication in EPJC)