A reappraisal of the wrong-sign $hb\overline{b}$ coupling and the study of $h \rightarrow Z \gamma$

TL;DR

This paper reexamines the possibility of a negative $h b\overline{b}$ coupling in two Higgs doublet models, emphasizing the roles of $h \rightarrow VV$, $h \rightarrow Z \gamma$, and $h \rightarrow \gamma \gamma$ measurements in constraining this scenario.

Contribution

It provides a detailed analysis of how current and future measurements of Higgs decay channels impact the sign of the $h b\overline{b}$ coupling in two Higgs doublet models, especially the Flipped model.

Findings

$h \rightarrow VV$ decays are crucial for understanding the coupling sign.

$h \rightarrow Z \gamma$ and $h \rightarrow \gamma \gamma$ are less sensitive to production mechanism inputs.

Searches for $h \rightarrow Z \gamma$ can influence the determination of the $h b\overline{b}$ coupling sign.

Abstract

It has been pointed out recently that current experiments still allow for a two Higgs doublet model where the $h b \bar{b}$ coupling ($k_D m_b/v$) is negative; a sign opposite to that of the Standard Model. Due to the importance of delayed decoupling in the $h H^+ H^-$ coupling, $h \rightarrow \gamma \gamma$ improved measurements will have a strong impact on this issue. For the same reason, measurements or even bounds on $h \rightarrow Z \gamma$ are potentially interesting. In this article, we revisit this problem, highlighting the crucial importance of $h \rightarrow VV$, which can be understood with simple arguments. We show that the impacts on $k_D<0$ models of both $h \rightarrow b \bar{b}$ and $h \rightarrow \tau^+ \tau^-$ are very sensitive to input values for the gluon fusion production mechanism; in contrast, $h \rightarrow \gamma \gamma$ and $h \rightarrow Z \gamma$ are not. We also inquire if the search for $h \rightarrow Z \gamma$ and its interplay with $h \rightarrow \gamma \gamma$ will impact the sign of the $h b \bar{b}$ coupling. Finally, we study these issues in the context of the Flipped two Higgs doublet model.