A light pseudoscalar of 2HDM confronted with muon g-2 and experimental constraints

TL;DR

This paper investigates the viability of a light pseudoscalar in the lepton-specific 2HDM to explain muon g-2 anomalies while satisfying experimental constraints, revealing tight parameter restrictions and a preference for wrong-sign Yukawa couplings.

Contribution

It provides a detailed analysis of the parameter space for a light pseudoscalar in 2HDM considering multiple experimental constraints, highlighting the allowed mass range and coupling regions.

Findings

Pseudoscalar mass can be as low as 10 GeV under constraints.

Strong restrictions on $ aneta$, $eta- ext{alpha}$, and charged Higgs mass.

Preference for wrong-sign Yukawa coupling region.

Abstract

A light pseudoscalar of the lepton-specific 2HDM can enhance the muon g-2, but suffer from various constraints easily, such as the 125.5 GeV Higgs signals, non-observation of additional Higgs at the collider and even $B_s\to \mu^+\mu^-$. In this paper, we take the light CP-even Higgs as the 125.5 GeV Higgs, and examine the implications of those observables on a pseudoscalar with the mass below the half of 125.5 GeV. Also the other relevant theoretical and experimental constraints are considered. We find that the pseudoscalar can be allowed to be as low as 10 GeV, but the corresponding $\tan\beta$, $\sin(\beta-\alpha)$ and the mass of charged Higgs are strongly constrained. In addition, the surviving samples favor the wrong-sign Yukawa coupling region, namely that the 125.5 GeV Higgs couplings to leptons have opposite sign to the couplings to gauge bosons and quarks.