Electron and muon g−2 anomalies in general flavor conserving two-Higgs-doublet models

Abstract

In general two-Higgs-doublet models (2HDMs) without scalar flavor changing neutral couplings (SFCNC) in the lepton sector, the electron, muon, and tau interactions can be decoupled in a robust framework, stable under renormalization group evolution. In this framework, the breaking of lepton flavor universality (LFU) goes beyond the mass proportionality, opening the possibility to accommodate in a simple manner a different behavior among charged leptons. We analyze simultaneously the electron and muon (g − 2) anomalies in the context of these general flavor conserving models in the leptonic sector (glFC). We consider two different models, I-glFC and II-glFC, in which the quark Yukawa couplings coincide, respectively, with the ones in type I and in type II 2HDMs. We find two types of solutions that fully reproduce both (g − 2) anomalies, and which are compatible with experimental constraints from LEP and LHC, from LFU, from flavor and electroweak physics, and with theoretical constraints in the scalar sector. In the first type of solution, all the new scalars have masses in the 1-2.5 TeV range, the vacuum expectation values (vevs) of both doublets are quite similar in magnitude, and both anomalies are dominated by two loop Barr-Zee contributions. This solution appears in both models. There is a second type of solution, where one loop contributions are dominant in the muon anomaly, all new scalars have masses below 1 TeV, and the ratio of vevs is in the range 10-100. The second neutral scalar H is the lighter among the new scalars, with a mass in the 210-390 GeV range while the pseudoscalar A is the heavier, with a mass in the range 400-900 GeV. The new charged scalar H AE is almost degenerate either with the scalar or with the pseudoscalar. This second type of solution only appears in the I-glFC model. Both solutions require the soft breaking of the Z 2 symmetry of the Higgs potential.

Power-aligned 2HDM: a correlative perspective on (g − 2)e,μ

“…where ζ f are flavor-universal proportionality parameters. In the gA2HDM [24][25][26][27], on the other hand, the parameters ζ f are promoted to be diagonal matrices with three independent entries in the mass-eigenstate basis. It is readily seen that the FCNC effects are absent at tree level in both cases.…”

“…Such a quasi-linear tendency is also visualized in the right plot of figure 2. Note that if the NP Yukawa couplings of electron and muon are entirely independent, as is the case in the gA2HDM [24,25], there would be no correlation between ∆a µ and ∆a e , even when the 1σ interval of ∆a e,µ can be fitted. Thus, such a correlative explanation makes the pA2HDM distinguishable from other 2HDM candidates.…”

“…This is because the linear alignment is flavor-universal and an explanation of ∆a µ fixes already the parameter space in which a totally positive NP effect on ∆a e should arise. However, if one promotes the linearly aligned parameter ζ to a diagonal matrix, ζ = diag(ζ 1 , ζ 2 , ζ 3 ), with three independent entries ζ i , a simultaneous explanation of both ∆a e and ∆a µ anomalies can still be achieved [24,25]. Such a generalized A2HDM (gA2HDM) [26,27], nevertheless, enlarges the degrees of freedom of the model parameters and makes the simultaneous explanation of the ∆a e,µ anomalies non-correlative.…”

“…Within the power-aligned 2HDM (pA2HDM) proposed here, instead, the resolution of ∆a e,µ can alleviate the constraints from these leptonic precision observables, because, on the one hand, the new Higgs mass spectrum is now quasi-degenerate, rendering some cancellations among the quantum corrections, and, on the other hand, the power enhancement in the electron and muon Yukawa entries necessary for the ∆a e,µ explanation increases the tau Yukawa coupling at a speed slower than that in the linear alignment. Furthermore, being distinguishable from the gA2HDM that addresses the ∆a e,µ anomalies in a non-correlative manner [24,25], the pA2HDM predicts an interesting correlation between the two anomalies, which can be therefore tested by future precise measurements [79][80][81].…”

( g−2 ) anomalies and neutrino mass

“…Simple Z 0 (dark photon) models cannot account for both discrepancies [20]. Several papers studying both anomalies in different contexts can be found in the literature [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38].…”