Flavor Symmetry Research Articles

Flavor symmetries in an SU(5) model of grand unification

We investigate the options for imposing flavor symmetries on a minimal renormalizable non-supersymmetric SU(5) grand unified theory, without introducing additional flavor-related fields. Such symmetries reduce the number of free parameters in the model and therefore lead to more predictive models. We consider the Yukawa sector of the Lagrangian, and search for all possible flavor symmetries. As a result, we find 25 distinct realistic flavor symmetry cases, with ℤ2, ℤ3, ℤ4, and U(1) symmetries, and no non-Abelian cases.

Results of analysis of Σ+p scattering events in J-PARC E40 experiment: differential cross sections and phase shifts of 3S1 and 1P1 states

We performed a novel Σ+p scattering experiment at the J-PARC Hadron Experimental Facility. Approximately 2400 Σ+p scattering events were identified by a kinematical consistency check for the recoil proton. The differential cross sections of the Σ+p elastic scattering were derived with better precision than in previous experiments. By exploiting high-quality differential cross section data and the simple representation of Σ+p interaction in the SU(3) flavor symmetry, we performed a phase-shift analysis on hyperon-nucleon scattering data for the first time. The absolute value of the phase shift of the 3S1 channel, where a large repulsive force was predicted due to the Pauli exclusive effect between quarks, was evaluated. These results indicate that the interaction of the 3S1 channel in the Σ+p channel is moderately repulsive, as the Nijmegen extended-soft-core models predicted.

Revisiting rescattering contributions to overline{B} (s) \u2192 {D}_{(s)}^{left(ast right)}M decays

Motivated by the reported discrepancies between experimental data and Standard Model predictions for the branching ratios of the color-allowed decays overline{B} 0 → D(*)+K− and {overline{B}}_s^0 → {D}_s^{left(ast right)+}{pi}^{-} , we study final-state rescattering effects on overline{B} (s) → {D}_{(s)}^{left(ast right)}P and overline{B} (s) → D(s)V, where P(V) is a light pseudoscalar (vector) meson. We consider quasi-elastic rescatterings in the framework of SU(3) and U(3) flavor symmetries, and find that the effects cannot explain the measured branching ratios of the color-allowed and color-suppressed decays simultaneously. We also perform global fits to the overline{B} (s) → {D}_{(s)}^{left(ast right)}P and overline{B} (s) → D(s)V data, allowing for new physics contributions to the Wilson coefficient a1 associated with the color-allowed tree amplitudes. It is shown that the fits prefer a downward shift of mathcal{O} (10%) in a1 even in the presence of the quasi-elastic rescattering contributions.

Exploration of in-medium hyperon-nucleon interactions

The study focuses on exploring the changes in the hyperon-baryon interaction at various nuclear densities. This approach starts by building a vacuum hyperon-nucleon interaction model based on Boson -Exchange maintaining SU(3) flavor symmetry. Bethe-Goldstone equation is then explored to investigate the medium properties over the bare interaction. A detailed investigation of the density dependence revealed clear changes in the low energy parameters with the variation of the medium density shown for different strangeness channels.

Collider signatures of vector-like fermions from a flavor symmetric model

We propose a model with two Higgs doublets and several SU(2) scalar singlets with a global non-Abelian flavor symmetry {mathcal{Q}}_6times {mathcal{Z}}_2 . This discrete group accounts for the observed pattern of fermion masses and mixing angles after spontaneous symmetry breaking. In this scenario only the third generation of fermions get their masses as in the Standard Model (SM). The masses of the remaining fermions are generated through a seesaw-like mechanism. To that end, the matter content of the model is enlarged by introducing electrically charged vector-like fermions (VLFs), right handed Majorana neutrinos and several SM scalar singlets. Here we study the processes involving VLFs that are within the reach of the Large Hadron Collider (LHC). We perform collider studies for vector-like leptons (VLLs) and vector-like quarks (VLQs), focusing on double production channels for both cases, while for VLLs single production topologies are also included. Utilizing genetic algorithms for neural network optimization, we determine the statistical significance for a hypothetical discovery at future LHC runs. In particular, we show that we can not safely exclude VLLs for masses greater than 200 GeV. For VLQ’s in our model, we show that we can probe their masses up to 3.8 TeV, if we take only into account the high-luminosity phase of the LHC. Considering Run-III luminosities, we can also exclude VLQs for masses up to 3.4 TeV. We also show how the model with predicted VLL masses accommodates the muon anomalous magnetic moment.

Nonzero θ13 with A4 × Z4 Flavor Symmetry Group

Nonzero θ13 with A4 × Z4 Flavor Symmetry Group

Radiative Xi _{b}^{-}rightarrow Xi ^{-}gamma decay

Recently, the LHCb Collaboration performed first search for the rare radiative Xi _{b}^{-}rightarrow Xi ^{-}gamma decay and put an upper limit, mathcal{B}(Xi _{b}^{-}rightarrow Xi ^{-}gamma ) < 1.3 times 10^{-4}, on its branching ratio. The measurement agrees well with existing theory prediction using SU(3) flavor symmetry method, but shows a slight tension with the previous prediction from light-cone sum rules. Inspired by this, we investigate this decay as well as other radiative decays of Xi _b^{0(-)}(Xi ^{'-}_{b}) to Xi ^{0(-)} and Sigma ^{0(-)} baryons using the form factors calculated from light-cone QCD sum rules in full theory. we obtain mathcal{B}(Xi _{b}^{-}rightarrow Xi ^{-}gamma )=1.08^{+0.63}_{-0.49} times 10^{-5} , which lies below the upper limit set by LHCb and is consistent with flavor-symmetry driven prediction. Our predictions on other channels may be checked in experiment and by other phenomenological approaches.

Quasi–eclectic modular flavor symmetries

Modular flavor symmetries provide us with a new, promising approach to the flavor problem. However, in their original formulation the kinetic terms of the standard model fields do not have a preferred form, thus introducing additional parameters, which limit the predictive power of this scheme. In this work, we introduce the scheme of quasi–eclectic flavor symmetries as a simple fix. These symmetries are the direct product of a modular and a traditional flavor symmetry, which are spontaneously broken to a diagonal modular flavor subgroup. This allows us to construct a version of Feruglio's model with the Kähler terms under control. At the same time, the starting point is reminiscent of what one obtains from explicit string models.

Neutrino and doubly charged Higgs boson phenomenology in flavored-TNMSSM

We develop a neutrino mass model based on A4×Z3 flavor symmetry in the context of the NMSSM extended by supersymmetric type II seesaw mechanism (flavored-TNMSSM). We show that the NMSSM-singlet contributes significantly to the light neutrino masses, leading to the trimaximal neutrino mixing and providing a source for CP violation. The model favors normal hierarchy for neutrino masses, and offers testable predictions for upcoming experiments aimed at developing the measurements of the parameters mνe, |mee|. We also show that the decay of the doubly charged Higgs boson (DCHB) into dilepton of the same sign is dominant; and that the muon-tau (μτ) channel is the most relevant, thus giving rise to a collider signature. We prove that the model allows LFV processes, such as τ±→e±μ∓e± and τ±→μ±e∓μ±. We find further that when the triplet VEV exceeds 0.5 eV, a discovery of the DCHB would be possible at the current run of the LHC; whereas for a broad part of the parameter space when the triplet VEV is less than about 0.5 eV, the DCHB can acquire mass up to few TeVs, which can be probed at HL-LHC, HE-LHC, and future 100 TeV hadron colliders.

Revisiting semileptonic B−→pp¯ℓ−ν¯ℓ decays

We systematically revisit the baryonic four-body semileptonic decays of $B^- \to {\bf B}\bar{\bf B}'\ell^- \bar{\nu}_{\ell}$ by the perturbative QCD counting rules with ${\bf B}$ representing octet baryons and $\ell=e,\mu$. We study the transition form factors of $B^- \to {\bf B} \bar{\bf B}'$ in the limit of $(p_{\bf B}+p_{\bar{\bf B}'})^2 \to \infty $ with the three-body $\bar{B}\to {\bf B}\bar{\bf B}' M$ and $B^- \to p\bar{p} \mu^- \bar{\nu}_{\mu}$ data along with $SU(3)_f$ flavor symmetry. We calculate the decay branching ratios and angular asymmetries as well as the differential decay branching fractions of $B^- \to p \bar{p} \ell^- \bar{\nu}_{\ell}$. In particular, we find that our new result of ${\cal B}( B^- \to p \bar{p} \ell^- \bar{\nu}_{\ell})=(5.21\pm0.34)\times 10^{-6}$, which is about one order of magnitude lower than the previous theoretical prediction of $(10.4\pm2.9)\times 10^{-5}$, agrees well with both experimental measurements of $(5.8^{+2.6}_{-2.3})\times 10^{-6}$ and $(5.3\pm0.4)\times 10^{-6}$ by the Belle and LHCb Collaborations, respectively. We also evaluate the branching ratios and angular asymmetries in other channels of $B^- \to {\bf B}\bar{\bf B}\ell^- \bar{\nu}_{\ell}$, which can be tested by the ongoing experiments at LHCb and BelleII.

Deviation from tri-bimaximal mixing as a result of modification of Yukawa coupling structure of constrained sequential dominance

Tri-bimaximal mixing (TBM) in the neutrino sector has been obtained in constrained sequential dominance where the Yukawa couplings of righ-handed neutrinos have some particular structure. Current neutrino oscillation data suggests that neutrino mixing should deviate from TBM mixing pattern. To explain it, we propose a phenomenological model by adding some small complex parameters to the Yukawa couplings of CSD. Using this we have shown that neutrino mixing angles can deviate from their TBM values. We justify the modified form of Yukawa couplings of our work by constructing a model based on flavor symmetry.

Neutrino Masses and Leptogenesis in a Le − Lμ − Lτ model

We present a simple extension of the Standard Model with three right-handed neutrinos in a SUSY framework, with an additional U(1)F abelian flavor symmetry with a non standard leptonic charge for lepton doublets and arbitrary right-handed charges. We show how it is possible to provide the correct predictions for the mixing angles of the PMNS matrix and for the parameter with a moderate fine tuning. The baryon asymmetry of the Universe is generated via thermal leptogenesis through CP-violating decays of the heavy right-handed neutrinos. We present a detailed numerical solution of the relevant Boltzmann equation accounting for the impact of the distribution of the asymmetry in the lepton flavors.

Modularity of supersymmetric partition functions

We discover a modular property of supersymmetric partition functions of supersymmetric theories with R-symmetry in four dimensions. This modular property is, in a sense, the generalization of the modular invariance of the supersymmetric partition function of two-dimensional supersymmetric theories on a torus i.e. of the elliptic genus. The partition functions in question are on manifolds homeomorphic to the ones obtained by gluing solid tori. Such gluing involves the choice of a large diffeomorphism of the boundary torus, along with the choice of a large gauge transformation for the background flavor symmetry connections, if present. Our modular property is a manifestation of the consistency of the gluing procedure. The modular property is used to rederive a supersymmetric Cardy formula for four dimensional gauge theories that has played a key role in computing the entropy of supersymmetric black holes. To be concrete, we work with four-dimensional mathcal{N} = 1 supersymmetric theories but we expect versions of our result to apply more widely to supersymmetric theories in other dimensions.

1-form symmetry, isolated mathcal{N} = 2 SCFTs, and Calabi-Yau threefolds

We systematically study 4D mathcal{N} = 2 superconformal field theories (SCFTs) that can be constructed via type IIB string theory on isolated hypersurface singularities (IHSs) embedded in ℂ4. We show that if a theory in this class has no mathcal{N} = 2-preserving exactly marginal deformation (i.e., the theory is isolated as an mathcal{N} = 2 SCFT), then it has no 1-form symmetry. This situation is somewhat reminiscent of 1-form symmetry and decomposition in 2D quantum field theory. Moreover, our result suggests that, for theories arising from IHSs, 1-form symmetries originate from gauge groups (with vanishing beta functions). One corollary of our discussion is that there is no 1-form symmetry in IHS theories that have all Coulomb branch chiral ring generators of scaling dimension less than two. In terms of the a and c central charges, this condition implies that IHS theories satisfying a<frac{1}{24}left(15r+2fright) and c<frac{1}{6}left(3r+fright) (where r is the complex dimension of the Coulomb branch, and f is the rank of the continuous 0-form flavor symmetry) have no 1-form symmetry. After reviewing the 1-form symmetries of other classes of theories, we are motivated to conjecture that general interacting 4D mathcal{N} = 2 SCFTs with all Coulomb branch chiral ring generators of dimension less than two have no 1-form symmetry.

Proper-time evaluation of the effective action: Unequal masses in the loop

The Fock-Schwinger proper-time method is used to derive the effective action in the field theory with the chiral $U(3)\times U(3)$ symmetry explicitly broken by unequal masses of heavy particles. The one-loop effective action is presented as a series in inverse powers of heavy masses. The first two Seeley-DeWitt coefficients of this expansion are explicitly calculated. This powerful technique opens a promising avenue for studying explicit flavor symmetry breaking effects in the effective field theories.

Composite flavon-Higgs models

We consider a composite Higgs model based on the $SU(6)/Sp(6)$ coset, where an $U(1)$ subgroup of $Sp(6)$ is identified as the flavor symmetry. A complex scalar field $s$, which is a pseudo-Nambu-Goldstone boson of the broken symmetry, carries a flavor charge and plays the role of a flavon field. The $U(1)_F$ flavor symmetry is then broken by a VEV of the flavon field, which leads to a small parameter and generates the mass hierarchy between the top and bottom quarks. A light flavon below the TeV scale can be naturally introduced, which provides a fully testable model for the origin of flavor hierarchy. A light flavon also leads to substantial flavor changing neutral currents, which are strongly constrained by the flavor precision tests. The direct search of additional scalar bosons can also be conducted in HL-LHC and future hadron colliders.

E-string quantum curve

In this work we study the quantisation of the Seiberg-Witten curve for the E-string theory compactified on a two-torus. We find that the resulting operator expression belongs to the class of elliptic quantum curves. It can be rephrased as an eigenvalue equation with eigenvectors corresponding to co-dimension 2 defect operators and eigenvalues to co-dimension 4 Wilson surfaces wrapping the elliptic curve, respectively. Moreover, the operator we find is a generalised version of the van Diejen operator arising in the study of elliptic integrable systems. Although the microscopic representation of the co-dimension 4 defect only furnishes an SO(16) flavour symmetry in the UV, we find an enhancement in the IR to representations in terms of affine E8 characters. Finally, using the Nekrasov-Shatashvili limit of the E-string BPS partition function, we give a path integral derivation of the quantum curve.

Weak-Field Hall Resistivity and Spin-Valley Flavor Symmetry Breaking in Magic-Angle Twisted Bilayer Graphene.

Near a magic twist angle, the lowest energy conduction and valence bands of bilayer graphene moiré superlattices become extremely narrow. The band dispersion that remains is sensitive to the moiré's strain pattern, nonlocal tunneling between layers, and filling-factor-dependent Hartree and exchange band renormalizations. In this Letter, we analyze the influence of these band-structure details on the pattern of flavor symmetry breaking observed in this narrow band system and on the associated pattern of Fermi surface reconstructions revealed by weak-field Hall and Shubnikov-de Haas magnetotransport measurements.

The study of doubly charmed pentaquark c c {bar{q}}qq with the SU(3) symmetry

We study the masses and lifetimes of doubly charmed pentaquark P_{cc{bar{q}}qq}(q=u,d,s) primarily. The operation of masses carried out by the doubly heavy triquark-diquark model, whose results suggests the existence of stable states cc{bar{s}} ud with the parity J^P=frac{1}{2}^-. The roughly calculation about lifetimes show the short magnitudes, (4.65^{+0.71}_{-0.55})times 10^{-13}s for the parity J^P=frac{1}{2}^- and (0.93^{+0.14}_{-0.11})times 10^{-12} s for J^P=frac{3}{2}^-. Since the pentaquark cc{bar{s}} ud is interpreted as the stable bound states against strong decays, then we will focus on the production and possible decay channels of the pentaquark in the next step, the study would be fairly valuable supports for future experiments. For completeness, we systematically studied the production from Omega _{ccc} and the decay modes in the framework SU(3) flavor symmetry, including the processes of semi-leptonic and two body non-leptonic decays. Synthetically, we make a collection of the golden channels.

Leptogenesis, fermion masses and mixings in a SUSY SU(5) GUT with D4 flavor symmetry

We propose a model of fermion masses and mixings based on SU(5) grand unified theory (GUT) and a D4 flavor symmetry. This is a highly predictive 4D SU(5) GUT with a flavor symmetry that does not contain a triplet irreducible representation. The Yukawa matrices of quarks and charged leptons are obtained after integrating out heavy messenger fields from renormalizable superpotentials while neutrino masses are originated from the type I seesaw mechanism. The group theoretical factors from 24- and 45-dimensional Higgs fields lead to ratios between the Yukawa couplings in agreement with data, while the dangerous proton decay operators are highly suppressed. By performing a numerical fit, we find that the model captures accurately the mixing angles, the Yukawa couplings and the CP phase of the quark sector at the GUT scale. The neutrino masses are generated at the leading order with the prediction of trimaximal mixing while an additional effective operator is required to account for the baryon asymmetry of the universe (BAU). The model is remarkably predictive because only the normal neutrino mass ordering and the lower octant of the atmospheric angle are allowed while the CP conserving values of the Dirac neutrino phase δCP are excluded. Moreover, the predicted values of the effective Majorana mass mββ can be tested at future neutrinoless double beta decay experiments. An analytical and a numerical study of the BAU via the leptogenesis mechanism is performed. We focused on the regions of parameter space where leptogenesis from the lightest right-handed neutrino is successfully realized. Strong correlations between the parameters of the neutrino sector and the observed BAU are obtained.