On stringy origin of minimal flavor violation

We study the minimal flavor violation in the context of string effective field theory. Stringy selection rules indicate that n-point couplings among fermionic zero-modes and lightest scalar modes in the string effective action are given by a product of Yukawa couplings which are regarded as spurion fields of stringy and geometrical symmetries. Hence, Yukawa couplings determine the dynamics of flavor and CP violations. This observation strongly supports the hypothesis of minimal flavor violation in the Standard Model effective field theory.

Radiative lepton mass and muon g − 2 with suppressed lepton flavor and CP violations

The recent experimental status, including the confirmation of the muon g − 2 anomaly at Fermilab, indicates a Beyond Standard Model (BSM) satisfying the following properties: 1) it enhances the g − 2 2) suppresses flavor violations, such as μ → eγ, 3) suppresses CP violations, such as the electron electric dipole moment (EDM). In this letter, I show that the eigenbasis of the mass matrix and higher dimensional photon operators can be automatically aligned if the masses of heavy leptons are generated radiatively together with the g − 2. As a result, the muon g − 2 is enhanced but the EDM of the electron and μ → eγ rate are naturally suppressed. Phenomenology and applications of the mechanism to the B-physics anomalies are argued.

The framework for a common origin of $$\delta _{\mathrm{CKM}}$$ and $$\delta _{\mathrm{PMNS}}$$

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 complex Yukawa couplings, both in the quark and lepton sectors, the above connection is not possible in general, since Yukawa 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 $$\mathrm{h}\rightarrow e^\pm \tau ^\mp $$ h → e ± τ ∓ and $$t\rightarrow \mathrm{h}c$$ t → h c . The connection between CP violations in CKM and PMNS is explicitely illustrated in models with Minimal Flavour Violation.

A novel strategy for searching for CP violations in the baryon sector

Despite the large baryon-anti-baryon asymmetry in the observable Universe, the closely related phenomenon — the violation of the combined charge and parity symmetry (CPV) — has not been observed in the baryon sector in laboratories. In this paper, a new strategy for searching for CPV in heavy hadron multi-body decays is proposed, in which a set of novel observables measuring CPV in such decays — the partial wave CP asymmetries (PWCP As) — are introduced. This strategy is model-independent and applicable to multi-body decays of heavy hadrons with arbitrary spin configurations in both initial and final states, and with any number of particles in the final state. It is especially applicable for CPV investigations in multi-body decays of heavy baryons. As applications of this strategy, we suggest to measure the PWCP As in some decay channels of bottom baryons such as $$ {\Lambda}_b^0\to p{\pi}^{-}{\pi}^{+}{\pi}^{-} $$ Λ b 0 → p π − π + π − , Λb → pK−π+π−, $$ {\Lambda}_b^0\to p{\pi}^{-}{K}^{+}{K}^{-} $$ Λ b 0 → p π − K + K − , $$ {\Lambda}_b^0\to \Lambda {K}^{+}{\pi}^{-} $$ Λ b 0 → Λ K + π − , and $$ {\Lambda}_b^0\to p{\pi}^{-}{K}_s $$ Λ b 0 → p π − K s .

The common origin of the family mass hierarchy and CP violation from flavor-dependent vacuum for quarks and leptons

We rewrite the Yukawa interactions of the Standard Model in terms of flavor-dependent vacuum structure to address the family mass hierarchy and CP violation in both the quark sector and lepton sector. It is realized that Yukawa terms only include the same number of degrees of freedom as phenomenological observables with no requirement of extra particle or any new symmetry. The quark and lepton mass hierarchy arises as a natural result of the close-to-flat vacuum in flavor space. The CP violations in CKM mixing and PMNS mixing are explained as general quantum phases between weak gauge eigenstates and Yukawa interaction states. The mechanism is proven by reproduction of all current quark/lepton mass data and the CKM/PMNS mixing parameters.

The CP violation and scalar dark matter in a 331 model

The 331 model with right-handed neutrinos is reassessed to investigate the CP violation in the quark sector. After the spontaneous symmetry breaking, the masses and physical fields of the particle content are obtained. The fermions content of the 331 model is enlarged to include exotic quarks with known electric charge and with masses defined at the TeV scale. The existence of these exotic quarks induces extra CP violations via couplings with quarks of the Standard Model mediated by charged gauge boson with mass fixed at the TeV scale. An extra discrete [Formula: see text] symmetry is introduced in the 331 model to get a stable scalar field that can be a candidate to the dark matter content. The new scalar field interacts at the tree level with the [Formula: see text] gauge boson that works as a dark matter portal. The relic density associated with the scalar field is calculated to yield the solution mass that satisfies the observed dark matter. The region allowed on the parameter space of the dark matter mass versus [Formula: see text] mass is obtained to include the bounds of PANDAX2017, XENON1T(2t.y) and LUX experiments.

Dealing with T and CPT violations in mixing as well as direct and indirect CP violations for neutral mesons decaying to two vectors

A large number of observables can be constructed from differential decay rate based on the polarization of final state while considering decay of a neutral meson $$(P^{0} \text { or } {\bar{P}}^{0})$$(P0orP¯0) to two vector particles. But all of these observables are not independent to each other since there are only a few independent theoretical parameters controlling the whole dynamics and therefore various relations among observables emerge. In this paper, we have studied the behaviour of observables for neutral meson decaying to two vectors in presence of $$T$$T and $$C\!P T$$CPT violations in mixing accompanied by both direct and indirect $$C\!P$$CP violations. We have expressed all of the fourteen unknown theoretical parameters for this scenario in terms observables only and constructed the complete set of thirty four relations among observables whose violation would signify the existence of some new Physics involving direct violation of $$C\!P T$$CPT. In addition, using this formalism we have studied three special cases too: (a) SM scenario, (b) SM plus direct $$C\!P$$CP violation (c) SM plus $$T$$T and $$C\!P T$$CPT violation in mixing.

CP violations in a predictive A4 symmetry model

We will investigate numerically a seesaw model with $A_4$ flavor symmetry to find allowed regions satisfying the current experimental neutrino oscillation data, then use them to predict physical consequences. Namely, the lightest active neutrino mass is of the order of $\mathcal{O}(10^{-2})$ eV. The effective neutrino mass $|\langle m\rangle|$ associated with neutrinoless double beta decay is in the range $[0.002 \,\mathrm{eV},0.038\,\mathrm{eV}]$ and $[0.048\,\mathrm{eV},0.058\,\mathrm{eV}]$, corresponding to the normal and the inverted hierarchy schemes, respectively. Other relations among relevant physical quantities are shown, so that they can be determined if some of them are confirmed experimentally. The recent data of the baryon asymmetry of the Universe ($\eta_B$) can be explained via leptogenesis caused by the effect of the renormalization group evolution on the Dirac Yukawa couplings, provided the right-handed neutrino mass scale $M_0$ ranges from $\mathcal{O}(10^8)$ GeV to $\mathcal{O}(10^{12})$ GeV for $\tan\beta =3$. This allowed $M_0$ range is different from the scale of $\mathcal{O}(10^{13})$ GeV for other effects that also generate a consistent $\eta_B$ from leptogenesis. The branching ratio of the decay $ \mu \rightarrow\,e\gamma$ may reach future experimental sensitivity for very light values of $M_0$. Hence, it will be inconsistent with the $M_0$ range predicted from the $\eta_B$ data whenever this decay is detected experimentally.