Speaker
Description
Since the landmark discovery in 2012 of the h(125) Higgs boson at the LHC, it should be a nobrainer to pursue the existence of a second Higgs doublet. We advocate, however, the general 2HDM
(g2HDM) that possesses a second set of Yukawa couplings. The extra top Yukawa coupling ρtt drives
electroweak baryogenesis (EWBG), i.e. generating Baryon Asymmetry of the Universe (B.A.U.) with
physics at the electroweak scale — hence relevant at the LHC! At the same time, the extra electron
Yukawa coupling ρee keeps the balance towards the stringent ACME2018 & JILA2023 bounds on the
electron electric dipole moment (eEDM), spectacularly via the fermion mass and mixing hierarchies
observed in the Standard Model — Discovery could be imminent (possibly followed by nEDM echo)!
EWBG suggests that exotic Higgs bosons H, A, H⁺ in g2HDM ought to be sub-TeV in mass, with
effects naturally well-hidden so far by 1) flavor structure, i.e. the aforementioned fermion mass-mixing
hierarchies; and 2) the emergent alignment phenomenon (i.e. small h−H mixing) that suppresses
processes such as t → ch, with the equivalent best limit by CMS and ATLAS. It is then natural to
pursue direct search modes such as cg → tH/A → ttc(bar) with extra top Yukawa couplings ρtc and ρtt
that are not alignment-suppressed; the results have just been published by CMS in 3/2024, which was
preceded by ATLAS. CMS would now pursue cg → bH⁺ → btb(bar), as well as continue to study t →
ch and ttc(bar) by adding Run III data, all with discovery potential. CMS also continues to pursue Bs,d
→ μμ, where the result published in 2023 has changed the world view.
Belle II would probe g2HDM with precision flavor measurements such as B → μν, τν; a ratio
deviating from 0.0045 would provide a smoking-gun. The τ → μγ process would need a large dataset.
With H, A, H⁺ expected at 300−600 GeV hence ripe for LHC search, we pursue lattice simulation
studies of first order electroweak phase transition, a prerequisite for EWBG in the early Universe, the
main motivation for our program. We also investigate the Landau pole phenomenon of g2HDM Higgs
sector for a new strong interaction scale, which could prove crucial for the future of collider physics.
Thus, our Decadal Mission:
“Find the extra H, A, H⁺ bosons; Crack the Flavor code; Solve the Mysterious B.A.U.!"
