$h \to \Upsilon \gamma$ Decay: Smoking Gun Signature of Wrong-Sign $hb\bar{b}$ Coupling

TL;DR

This paper investigates how an unusual Higgs decay to Upsilon gamma can reveal a wrong-sign bottom-Higgs coupling, indicating new physics beyond the Standard Model.

Contribution

It demonstrates that a significantly enhanced $h o psilon \, ext{gamma}$ decay rate uniquely signals a wrong-sign $h b\bar{b}$ coupling, a novel probe for extended Higgs sectors.

Findings

Wrong-sign $h b\bar{b}$ coupling can enhance decay rate by nearly two orders of magnitude.

Enhanced decay rate serves as a smoking gun for extended Higgs sectors.

Observation at colliders would unambiguously indicate new physics.

Abstract

We perform a model-independent study of new physics effects in the Higgs decay $h \to \Upsilon \gamma$, focusing on scenarios that spoil the accidental cancellation between the direct and indirect amplitudes. After imposing all existing constraints from Higgs production and decay measurements, we find that a wrong-sign $h b\bar b$ coupling is the only viable scenario capable of enhancing the $h \to \Upsilon \gamma$ decay width by nearly two orders of magnitude. Therefore, an observation of a significantly enhanced $h \to \Upsilon \gamma$ rate at the LHC or future colliders would provide unambiguous evidence for a wrong-sign $h b\bar b$ coupling, directly pointing to the presence of an extended Higgs sector.