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Botella, F. J., Cornet-Gomez, F., & Nebot, M. (2020). Electron and muon g-2 anomalies in general flavor conserving two-Higgs-doublet models. Phys. Rev. D, 102(3), 035023–19pp.
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 (gtlFC). We consider two different models, I-gtlFC and II-gelFC, 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-+/- is almost degenerate either with the scalar or with the pseudoscalar. This second type of solution only appears in the I-gelFC model. Both solutions require the soft breaking of the Z(2) symmetry of the Higgs potential.
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Nebot, M. (2020). Bounded masses in two Higgs doublets models, spontaneous CP violation and Z(2) symmetry. Phys. Rev. D, 102(11), 115002–16pp.
Abstract: In two Higgs doublet models (2HDMs) shaped by some unbroken symmetry, imposing perturbativity requirements on the quartic couplings can imply that the allowed masses of all the fundamental scalars are bounded from above. This important property is analyzed in detail for the only two realistic 2HDMs with an exact symmetry, the case with Z(2) symmetry and the case with CP symmetry. It is also noticeable that one exception arises in each case: when the vacuum is assumed to respect the imposed symmetry, a decoupling regime can nevertheless appear without violating perturbativity requirements. In both models with an exact symmetry and no decoupling regime, soft symmetry breaking terms can however lead to a decoupling regime: the possibility that this regime might be unnatural, since it requires some fine-tuning, is also analyzed.
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Alves, J. M., Botella, F. J., Branco, G. C., Cornet-Gomez, F., & Nebot, M. (2021). The framework for a common origin of delta(CKM) and delta S-PMN. Eur. Phys. J. C, 81(8), 727–11pp.
Abstract: We analyse a possible connection between CP violations in the quark and lepton sectors, parametrised by the CKM and PMNS phases. If one assumes that CP breaking arises from complexYukawa couplings, both in the quark and lepton sectors, the above connection is not possible in general, sinceYukawa couplings in the two sectors have independent flavour structures. We show that both the CKM and PMNS phases can instead be generated by a vacuum phase in a class of two Higgs doublet models, and in this case a connection may be established. This scenario requires the presence of scalar FCNC at tree level, both in the quark and lepton sectors. The appearance of these FCNC is an obstacle and a blessing. An obstacle since one has to analyse which models are able to conform to the strict experimental limits on FCNC, both in the quark and lepton sectors. A blessing, because this class of models is falsifiable since FCNC arise at a level which can be probed experimentally in the near future, specially in the processes h up arrow e(+/-) t +/- and t -> hc. The connection between CP violations in CKM and PMNS is explicitely illustrated in models with Minimal Flavour Violation.
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Botella, F. J., Cornet-Gomez, F., Miro, C., & Nebot, M. (2022). Muon and electron g-2 anomalies in a flavor conserving 2HDM with an oblique view on the CDF M-W value. Eur. Phys. J. C, 82(10), 915–25pp.
Abstract: We consider a type I or type X two Higgs doublets model with a modified lepton sector. The generalized lepton sector is also flavor conserving but with the new Yukawa couplings completely decoupled from lepton mass proportionality. The model is one loop stable under renormalization group evolution and it allows to reproduce the g – 2 muon anomaly together with the different scenarios one can consider for the electron g – 2 anomaly, related to the Cesium and/or to the Rubidium recoilmeasurements of the fine structure constant. Thorough parameter space analyses are performed to constrain all the model parameters in the different scenarios, either including or not including the recent CDF measurement of the W boson mass. For light new scalars with masses in the 0.2-1.0 TeV range, the muon anomaly receives dominant one loop contributions; it is for heavy new scalars with masses above 1.2 TeV that two loop Barr-Zee diagrams are needed. The electron g-2 anomaly, if any, must always be obtained with the two loop contributions. The final allowed regions are quite sensitive to the assumptions about perturbativity of Yukawa couplings, which influence unexpected observables like the allowed scalar mass ranges. On that respect, intermediate scalar masses, highly constrained by direct LHC searches, are allowed provided that the new lepton Yukawa couplings are fully scrutinized, including values up to 250 GeV. In the framework of a complete model, fully numerically analysed, we show the implications of the recent M-W measurement.
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Bernabeu, J., Botella, F. J., Nebot, M., & Segarra, A. (2022). B-0 – (B)over-bar(0) entanglement for an ideal experiment for the direct CP violation phi(3)/gamma phase. Phys. Rev. D, 106(5), 054026–7pp.
Abstract: B-0-(B) over bar0 entanglement offers a conceptual alternative to the single charged B-decay asymmetry for the measurement of the direct CP-violating gamma/phi(3) phase. With f = J/Psi(L); J/Psi K-S and g = (pi pi)(0); (rho(L)rho(L))(0), the 16 time-ordered double-decay rate intensities to (f, g) depend on the relative phase between the f- and g-decay amplitudes given by gamma at tree level. Several constraining consistencies appear. An intrinsic accuracy of the method at the level of +/- 1 degrees could be achievable at Belle-II with an improved determination of the penguin amplitude to g channels from existing facilities.
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