P-even, CP-violating Signals in Scalar-Mediated Processes

TL;DR

This paper explores new scalar-mediated processes that can reveal P-even, CP-violating signals in Higgs physics, especially in the Higgs alignment limit, and evaluates their detectability at future colliders.

Contribution

It identifies and analyzes processes that remain sensitive to P-even CP violation in the Higgs alignment limit, extending previous studies and assessing their discovery potential at future colliders.

Findings

Certain processes do not vanish in the Higgs alignment limit.

Future multi-TeV colliders can potentially detect these P-even CP-violating signals.

Loop-induced phenomena may also be observable.

Abstract

Most studies of Higgs sector CP violation focus on the detection of CP-violating neutral Higgs-fermion Yukawa couplings, which yield P-odd, CP-violating phenomena. There is some literature on purely bosonic signatures of Higgs sector CP violation, where the simultaneous observation of three processes (suitably chosen) constitutes a signal of P-even CP violation. However, in the examples previously analyzed, some of the processes are strongly suppressed in the approximate Higgs alignment limit (corresponding to the existence of a Standard Model like Higgs boson as suggested by LHC data), in which case the proposed CP-violating signals are difficult to observe in practice. In this paper, we extend the existing literature by examining processes that do not vanish in the Higgs alignment limit and whose simultaneous observation would provide unambiguous evidence for scalar-mediated P-even CP violation. We assess the discovery potential of such signals at various future multi-TeV lepton (and $\gamma\gamma$) colliders. The potential for detecting loop-induced P-even, CP-violating phenomena is also considered.