In a general two Higgs doublet model, we study flavor changing neutral Higgs (FCNH) decays into leptons at hadron colliders, pp → φ 0 → τ ∓ µ ± +X, where φ 0 could be a CP-even scalar (h 0 , H 0 ) or a CP-odd pseudoscalar (A 0 ). The light Higgs boson h 0 is found to resemble closely the Standard Model Higgs boson at the Large Hadron Collider. In the alignment limit of cos(β − α) ∼ = 0 for h 0 -H 0 mixing, FCNH couplings of h 0 are naturally suppressed, but such couplings of the heavier H 0 , A 0 are sustained by sin(β − α) ≃ 1. We evaluate physics backgrounds from dominant processes with realistic acceptance cuts and tagging efficiencies. We find promising results for √ s = 14 TeV, which we extend further to √ s = 27 TeV and 100 TeV future pp colliders.

We investigate the prospects for discovering a top quark decaying into one light Higgs boson (h 0 ) along with a charm quark (c) in top quark pair production at the CERN Large Hadron Collider (LHC) and future hadron colliers. A general two Higgs doublet model is adopted to study the signature of flavor changing neutral Higgs (FCNH) interactions with t → ch 0 , followed by h 0 → W W * → ℓ + ℓ − + E / T , where h 0 is the CP-even Higgs boson and E / T stands for missing transverse energy from neutrinos. We study the discovery potential for this FCNH signal and physics background from dominant processes with realistic acceptance cuts as well as tagging and mistagging efficiencies. Promising results are found for the LHC running at 13 TeV and 14 TeV center-of-mass energy as well as future pp colliders at 27 TeV and 100 TeV.

Recent progress on muon g − 2 measurement prompts one to take it even more seriously. In the general two Higgs doublet model that allows extra Yukawa couplings, we take a simplified approach of single enhanced coupling. We fix the charged lepton flavor violating coupling, ρτµ = ρµτ , via the one-loop mechanism, for illustrative masses of the heavy scalar H and pseudoscalar A, where we assume mA = m H + . Since extra top Yukawa couplings are plausibly the largest, we turn on ρtt and find that LHC search for gg → H, A → τ µ gives more stringent bound than from τ → µγ with two-loop mechanism. Turning on a second extra top Yukawa coupling, ρtc, can loosen the bound on ρtt, but LHC constraints can again be more stringent than from B → Dµν vs Deν universality. This means that evidence for H, A → τ µ may yet emerge with full LHC Run 2 data, while direct search for τ ± µ ∓ bW + or tcbW + (plus conjugate) may also bear fruit.

Corda, Mosquera Cuesta and Lorduy Gòmez have shown that spherically symmetric stationary states can be used as a model for galaxies in the framework of the linearized R 2 gravity. Those states could represent a partial solution to the Dark Matter Problem. Here we discuss an improvement of this work. In fact, as the star density is a functional of the invariants of the associated Vlasov equation, we show that any of these invariants is in its turn a functional of the local energy and the angular momentum. As a consequence, the star density depends only on these two integrals of the Vlasov system. This result is known as the "Jeans theorem". In addition, we find an analogous of the historical Tolman-Oppenheimer-Volkov equation for the system considered in this paper.For the sake of completeness, in the final Section of the paper we consider two additional models which argue that Dark Matter could not be an essential element.

We study a search for the charged Higgs boson via e + e − → H + H − → c bcb at the 500 GeV ILC. In a general two Higgs doublet model without Z2 symmetry, extra Yukawa couplings ρtt and ρtc can drive baryogenesis, but searches at the HL-LHC may still go empty-handed if the couplings are relatively weak. Taking m H + mH mA 200 GeV, with ρtt, ρtc ∼ 0.1 and no h(125)-H mixing, H + → c b decay is dominant, and the c bcb final state is likely overwhelmed by QCD background at the LHC. We show that the electroweak production of H + H − at the ILC is discoverable with integrated luminosity of 1 ab −1 . Furthermore, we show that m H + can be extracted by requiring the two pairs of b and light jets be roughly equal in mass, without assuming the mass value. Thus, ILC can probe low mass Higgs bosons in multijet final states to complement HL-LHC in the future.