Programme

O.14 -- Oral, VCTP-51

Date: Tuesday, 4 August 2026

Time: 11:10 - 11:30

Sphalerons in the General Two-Higgs-Doublet Model

Eibun Senaha

Van Lang University

Baryon-number-violating processes in the electroweak theory are mediated by the sphaleron, an unstable static solution of the field equations. In the Standard Model (SM), the sphaleron energy is determined primarily by the ratio of the Higgs quartic coupling to the SU(2) gauge coupling, or equivalently by the Higgs-boson-to-$W$-boson mass ratio. Beyond the SM, however, the sphaleron energy can deviate from the SM prediction even when the observed 125 GeV Higgs boson mass and the $W$-boson mass are fixed. A precise determination of the sphaleron energy is therefore essential for assessing the viability of electroweak baryogenesis. In this talk, we investigate the sphaleron solution in the general two-Higgs-doublet model (g2HDM), in which no discrete symmetry is imposed. Taking into account current theoretical and experimental constraints, we quantify the impact of the $Z_2$-breaking quartic couplings $\lambda_6$ and $\lambda_7$, which are absent in the conventional $Z_2$-symmetric 2HDM, on the sphaleron energy. We also discuss the resulting sphaleron decoupling condition relevant to electroweak baryogenesis.

Presenter: Senaha Eibun