Flavor Symmetry Research Articles

Landscape of modular symmetric flavor models

We study the moduli stabilization from the viewpoint of modular flavor symmetries. We systematically analyze stabilized moduli values in possible configurations of flux compactifications, investigating probabilities of moduli values and showing which moduli values are favorable from our moduli stabilization. Then, we examine their implications on modular symmetric flavor models. It is found that distributions of complex structure modulus τ determining the flavor structure are clustered at a fixed point with the residual ℤ3 symmetry in the SL(2, ℤ) fundamental region. Also, they are clustered at other specific points such as intersecting points between |τ|2 = k/2 and Re τ = 0,±1/4,±1/2, although their probabilities are less than the ℤ3 fixed point. In general, CP-breaking vacua in the complex structure modulus are statistically disfavored in the string landscape. Among CP-breaking vacua, the values Re τ = ±1/4 are most favorable in particular when the axio-dilaton S is stabilized at Re S = ±1/4. That shows a strong correlation between CP phases originated from string moduli.

Fock–Schwinger Method in the Case of Different Masses

The result of removing heavy particles with different mass from the theory spectrum can be described at low energy by the effective action, which is an asymptotic series in inverse powers of the mass. It is demonstrated how the leading terms of the asymptotic series can be calculated on the basis of the Fock–Schwinger proper time method. Theory with broken $$U(3) \times U(3)$$ chiral symmetry is considered to illustrate this approach. It is shown that different masses lead to the formation of a set of vertices describing the effects of the explicit breaking of flavor symmetry, which are usually not revealed in a less rigorous consideration of the problem. The result can be used in the study of theories with spontaneous symmetry breaking and in the development of effective theories of the Standard Model.

Multiscalar B-L extension based on S 4 flavor symmetry for neutrino masses and mixing * *This research is funded by Vietnam National Foundation for Science and Technology Development (NAFOSTED) (103.01-2017.341)

A multiscalar and nonrenormalizable extension of the standard model (SM) with symmetry which successfully explains the recently observed neutrino oscillation data is proposed. The tiny neutrino masses and their hierarchies are generated via the type-I seesaw mechanism. The model reproduces the recent experiments of neutrino mixing angles and Dirac CP violating phase in which the atmospheric angle and the reactor angle get the best-fit values while the solar angle and Dirac CP violating phase ( ) are in range of the best-fit value for the normal hierarchy (NH). For the inverted hierarchy (IH), gets the best-fit value and together with are in the range, while is in range of the best-fit value. The effective neutrino masses are predicted to be for the NH and for the IH, in good agreement with the most recent experimental data.

Anomaly-free leptophilic axionlike particle and its flavor violating tests

Motivated by the recent Xenon1T result, we study a leptophilic flavour-dependent anomaly-free axion-like particle (ALP) and its effects on charged-lepton flavour violation (CLFV). We present two representative models. The first one considers that the ALP origins from the flavon that generates the charged-lepton masses. The second model assumes a larger flavour symmetry such that more general mixings in the charged-lepton are possible, while maintaining flavour-dependent ALP couplings. We find that a keV ALP explaining the Xenon1T result is still viable for lepton flavour violation and stellar cooling astrophysical limits. On the other hand, if the Xenon1T result is confirmed, future CLFV measurements can be complementary to probe such a possibility.

Flavour Symmetry Embedded - GLoBES (FaSE-GLoBES)

Neutrino models based on flavour symmetries provide a natural way to explain the origin of tiny neutrino masses. At the dawn of precision measurements of neutrino oscillation parameters, neutrino mass models can be constrained and examined by on-going and up-coming neutrino experiments. We present a supplemental tool Flavour Symmetry Embedded (FaSE) for General Long Baseline Experiment Simulator (GLoBES), and it is available on https://github.com/tcwphy/FASE_GLoBES. It can translate the neutrino mass model parameters into standard neutrino oscillation parameters and offer prior functions in a user-friendly way. We demonstrate the robustness of FaSE-GLoBES with four examples on how the model parameters can be constrained and whether the model is excluded by an experiment or not. We wish that this toolkit will facilitate the study of new neutrino mass models. Program summaryProgram title: FaSECPC Library link to program files:https://doi.org/10.17632/23bnpf2vps.1Developer’s repository link:https://github.com/tcwphy/FASE_GLoBESLicencing provisions: GNU General Public Licence 3Programming language: C/C++Nature of problem: The FaSE package serves to provide a toolkit for GLoBES for testing flavour symmetry models in neutrino oscillation experiments.Solution method: Two files are provided in FaSE: ‘FaSE_GLoBES.c’ and ‘model-input.c’. The function of ‘FaSE_GLoBES.c’ is to simulate the probability profile and implement the prior values for standard neutrino oscillation parameters, which are translated from the model parameters given by the user. While ‘FaSE_GLoBES.c’ does not need any modification, the user-defined input, which includes the model set up and any restrictions on the model parameters, are defined in ‘model-input.c’.Additional comments including restrictions and unusual features: This toolkit is not a standalone program, but it requires an installation of GLoBES version 3.0.0 or higher.

Neutrino mixing by modifying the Yukawa coupling structure of constrained sequential dominance

In the constrained sequential dominance (CSD), tri-bimaximal mixing (TBM) pattern in the neutrino sector has been explained, by proposing a certain Yukawa coupling structure for the right-handed neutrinos of the model. However, from the current experimental data it is known that the values of neutrino mixing angles are deviated from the TBM values. In order to explain this neutrino mixing, we first propose a phenomenological model where we consider Yukawa couplings which are modified from that of CSD. Essentially, we add small complex parameters to the Yukawa couplings of CSD. Using these modified Yukawa couplings, we demonstrate that neutrino mixing angles can deviate from their TBM values. We also construct a model, based on a flavor symmetry, in order to justify the modified form of Yukawa couplings of our work.

Strangeness S=−3 and S=−4 baryon-baryon interactions in relativistic chiral effective field theory

The strangeness $S=-3$ and $-4$ baryon-baryon interactions are investigated in the relativistic chiral effective field theory at leading order. First, the potentials are derived from the $S=-1$ sector assuming that the corresponding low-energy constants are related to each other via SU(3) flavor symmetry. The comparison with the state-of-the-art lattice QCD simulations, show, however, that SU(3) flavor symmetry breaking effects can not be neglected. In order to take into account these effects, we redetermine two sets of low-energy constants by fitting to the lattice QCD data in the $\Xi\Sigma$ and $\Xi\Xi$ channels respectively. The fitting results demonstrate that the lattice QCD $S$-waves phase shifts for both channels can be described rather well. Without any additional free low-energy constants, the predicted phase shifts for the ${}^3D_1$ channel and the mixing angle $\varepsilon_1$ are also in qualitative agreement with the lattice QCD data for the $S=-3$ channel, while the results for the $S=-4$ channel remain to be checked by future lattice QCD simulations. With the so-obtained low-energy constants, the $S$-wave scattering lengths and effective ranges are calculated for these two channels at the physical point. Finally, in combination with the $S=0$ and $-2$ results obtained in our previous works, we study the evolution of the irreducible representation $27$ in the baryon-baryon interactions as a function of increasing strangeness. It is shown that the attraction decreases dramatically as strangeness increases from $S=0$ to $S=-2$, but then remains relatively stable until $S=-4$. The results indicate that the existence of bound states in the $\Xi\Sigma$ and $\Xi\Xi$ channels is rather unlikely.

The eclectic flavor symmetry of the \u21242 orbifold

Modular symmetries naturally combine with traditional flavor symmetries and mathcal{CP} , giving rise to the so-called eclectic flavor symmetry. We apply this scheme to the two-dimensional ℤ2 orbifold, which is equipped with two modular symmetries SL(2, ℤ)T and SL(2, ℤ)U associated with two moduli: the Kähler modulus T and the complex structure modulus U. The resulting finite modular group is ((S3× S3) ⋊ ℤ4) × ℤ2 including mirror symmetry (that exchanges T and U) and a generalized mathcal{CP} -transformation. Together with the traditional flavor symmetry (D8× D8)/ℤ2, this leads to a huge eclectic flavor group with 4608 elements. At specific regions in moduli space we observe enhanced unified flavor symmetries with as many as 1152 elements for the tetrahedral shaped orbifold and leftlangle Trightrangle =leftlangle Urightrangle =exp left(frac{pi mathrm{i}}{3}right) . This rich eclectic structure implies interesting (modular) flavor groups for particle physics models derived form string theory.

Photoproduction of strange hidden-charm and hidden-bottom states

Recently BESIII collaboration discovered a charged strange hidden-charm state Z_{cs}(3985) in the D_s^-D^{*0} + D_s^{*-}D^{0} spectrum. A higher Z'_{cs} state coupling to {bar{D}}_s^{*-}D^{*0} is expected by SU(3)-flavor symmetry, and their bottom partners are anticipated by heavy quark flavor symmetry. Here we study the photoproduction of these exotic states and investigate carefully the background from Pomeron exchange. Our results indicate that the maximal photoproduction cross section of strange partner is around 1–2 orders of magnitude smaller than that of the corresponding non-strange states. The possibility of searching for them in future electron-ion colliders (EIC) is briefly discussed.

Is X(7200) the heavy anti-quark diquark symmetry partner of X(3872)?

The D^{(*)}Xi _{cc}^{(*)} system and {bar{Xi }}_{cc}^{(*)}Xi _{cc}^{(*)} system can be related to the D^{(*)}{bar{D}}^{(*)} system via heavy anti-quark di-quark symmetry (HADS). In this work, we employ a contact-range effective field theory to systematically investigate the likely existence of molecules in these systems in terms of the hypothesis that X(3872) is a 1^{++}~D{bar{D}}^{*} bound state in the isospin symmetry limit, with some of the unknown low energy constants estimated using the light-meson saturation approximation. In the meson–meson system, a J^{PC}=2^{++}~{bar{D}}^{*}D^{*} molecule commonly referred to as X(4013) is reproduced, which is the heavy quark spin partner of X(3872). In the meson-baryon system, we predict two triply charmed pentaquark molecules, J^{P}=1/2^{-}~D^{*}Xi _{cc} and J^{P}=5/2^{-}~D^{*}Xi _{cc}^{*}. In the baryon-baryon system, there exist seven di-baryon molecules, J^{PC}=0^{-+}~{bar{Xi }}_{cc}Xi _{cc}, J^{PC}=1^{--}~{bar{Xi }}_{cc}Xi _{cc}, J^{PC}=1^{-+}~{bar{Xi }}_{cc}Xi _{cc}^{*}, J^{PC}=1^{--}~{bar{Xi }}_{cc}Xi _{cc}^{*}, J^{PC}=2^{-+}~{bar{Xi }}_{cc}Xi _{cc}^{*}, J^{PC}=2^{-+}~{bar{Xi }}_{cc}^{*}Xi _{cc}^{*}, and J^{PC}=3^{--}~{bar{Xi }}_{cc}^{*}Xi _{cc}^{*}. Among them, the J^{PC}=0^{-+}~{bar{Xi }}_{cc}Xi _{cc} molecule may contribute to the X(7200) state recently observed by the LHCb Collaboration, which implies that X(7200) can be related to X(3872) via HADS. As a byproduct, with the heavy quark flavor symmetry we also study likely existence of molecular states in the B^{(*)}{bar{B}}^{(*)}, {bar{B}}^{(*)}Xi _{bb}^{(*)}, and {bar{Xi }}_{bb}^{(*)}Xi _{bb}^{(*)} systems.

Composite Dark Matter and a horizontal symmetry

We present a model of composite Dark Matter (DM), in which a new QCD-like confining “hypercolor” sector generates naturally stable hyperbaryons as DM candidates and at the same time provides mass to new weakly coupled gauge bosons H that serve as DM mediators, coupling the hyperbaryons to the Standard Model (SM) fermions. By an appropriate choice of the H gauge symmetry as a horizontal SU(2)h SM flavor symmetry, we show how the H gauge bosons can be identified with the horizontal gauge bosons recently put forward as an explanation for discrepancies in rare B-meson decays. We find that the mass scale of the H gauge bosons suggested by the DM phenomenology intriguingly agrees with the one needed to explain the rare B-decay discrepancies.

SUSY breaking constraints on modular flavor S3 invariant SU(5) GUT model

Modular flavor symmetry can be used to explain the quark and lepton flavor structures. The SUSY partners of quarks and leptons, which share the same superpotential with the quarks and leptons, will also be constrained by the modular flavor structure and show a different flavor(mixing) pattern at the GUT scale. So, in realistic modular flavor models with SUSY completion, constraints from the collider and DM constraints can also be used to constrain the possible values of the modulus parameter. In the first part of this work, we discuss the possibility that the S3 modular symmetry can be preserved by the fixed points of T2/ZN orbifold, especially from T2/Z2. To illustrate the additional constraints from collider etc on modular flavor symmetry models, we take the simplest UV SUSY-completion S3 modular invariance SU(5) GUT model as an example with generalized gravity mediation SUSY breaking mechanism. We find that such constraints can indeed be useful to rule out a large portion of the modulus parameters. Our numerical results show that the UV-completed model can account for both the SM (plus neutrino) flavor structure and the collider, DM constraints. Such discussions can also be applied straightforwardly to other modular flavor symmetry models, such as A4 or S4 models.

Coulomb and Higgs branches from canonical singularities. Part 0

Five- and four-dimensional superconformal field theories with eight supercharges arise from canonical threefold singularities in M-theory and Type IIB string theory, respectively. We study their Coulomb and Higgs branches using crepant resolutions and deformations of the singularities. We propose a relation between the resulting moduli spaces, by compactifying the theories to 3d, followed by 3d mathcal{N} = 4 mirror symmetry and an S-type gauging of an abelian flavor symmetry. In particular, we use this correspondence to determine the Higgs branch of some 5d SCFTs and their magnetic quivers from the geometry. As an application of the general framework, we observe that singularities that engineer Argyres-Douglas theories in Type IIB also give rise to rank-0 5d SCFTs in M-theory. We also compute the higher-form symmetries of the 4d and 5d SCFTs, including the one-form symmetries of generalized Argyres-Douglas theories of type (G, G′).

Gravitational wave signatures from discrete flavor symmetries

Non-Abelian discrete symmetries have been widely used to explain the patterns of lepton masses and flavor mixing. In these models, a given symmetry is assumed at a high scale and then is spontaneously broken by scalars (the flavons), which acquire vacuum expectation values. Typically, the resulting leading order predictions for the oscillation parameters require corrections in order to comply with neutrino oscillation data. We introduce such corrections through an explicit small breaking of the symmetry. This has the advantage of solving the cosmological problems of these models without resorting to inflation. The explicit breaking induces an energy difference or “bias” between different vacua and drives the evolution of the domain walls, unavoidably produced after the symmetry breaking, towards their annihilation. Importantly, the wall annihilation leads to gravitational waves which may be observed in current and/or future experiments. We show that a distinctive pattern of gravitational waves with multiple overlapped peaks is generated when walls annihilate, which is within the reach of future detectors. We also show that cosmic walls from discrete flavor symmetries can be cosmologically safe for any spontaneous breaking scale between 1 and 1018 GeV, if the bias is chosen adequately, without the need to inflate the walls away. We use as an example a particular A4 model in which an explicit breaking is included in right-handed neutrino mass terms.

A hybrid seesaw model and hierarchical neutrino flavor structures based on A4 symmetry

Abstract We propose a hybrid seesaw model based on $A_{4}$ flavor symmetry, which generates a large hierarchical flavor structure. In our model, tree-level and one-loop seesaw mechanisms predict different flavor structures in the neutrino mass matrix and generate a notable hierarchy among them. We find that such a hierarchical structure gives a large effective neutrino mass that can be accessible by next-generation neutrinoless double beta decay experiments. Majorana phases can also be predictable. The $A_{4}$ flavor symmetry in the model is spontaneously broken to the $Z_{2}$ symmetry, leading to a dark matter candidate that is assumed to be a neutral scalar field. The favored mass region of the dark matter is obtained by numerical computations of the relic abundance and the cross section of the nucleon. We also investigate the predictions of several hierarchical flavor structures based on $A_{4}$ symmetry for the effective neutrino mass and the Majorana phases, and find characteristic features depending on the hierarchical structures.

Hydrodynamics in lattice models with continuous non-Abelian symmetries

We develop a systematic effective field theory of hydrodynamics for many-body systems on the lattice with global continuous non-Abelian symmetries. Models with continuous non-Abelian symmetries are ubiquitous in physics, arising in diverse settings ranging from hot nuclear matter to cold atomic gases and quantum spin chains. In every dimension and for every flavor symmetry group, the low energy theory is a set of coupled noisy diffusion equations. Independence of the physics on the choice of canonical or microcanonical ensemble is manifest in our hydrodynamic expansion, even though the ensemble choice causes an apparent shift in quasinormal mode spectra. We use our formalism to explain why flavor symmetry is qualitatively different from hydrodynamics with other non-Abelian conservation laws, including angular momentum and charge multipoles.As a significant application of our framework, we study spin and energy diffusion in classical one-dimensional SU(2)-invariant spin chains, including the Heisenberg model along with multiple generalizations. We argue based on both numerical simulations and our effective field theory framework that non-integrable spin chains on a lattice exhibit conventional spin diffusion, in contrast to some recent predictions that diffusion constants grow logarithmically at late times. We show that the apparent enhancement of diffusion is due to slow equilibration caused by (non-Abelian) hydrodynamic fluctuations.

Neutrino observables from a U(2) flavor symmetry

We study the predictions for $CP$ phases and absolute neutrino mass scale for broad classes of models with a U(2)-like flavor symmetry. For this purpose we consider the same special textures in neutrino and charged lepton mass matrices that are successful in the quark sector. While in the neutrino sector the U(2) structure enforces two texture zeros, the contribution of the charged lepton sector to the Pontecorvo-Maki--Nakagawa--Sakata (PMNS) matrix can be parametrized by two rotation angles. Restricting to the cases where at least one of these angles is small, we obtain three representative scenarios. In all scenarios we obtain a narrow prediction for the sum of neutrino masses in the range of 60--75 meV, possibly in the reach of upcoming galaxy survey experiments. All scenarios can be excluded if near-future experimental date provide evidence for either neutrinoless double-beta decay or inverted neutrino mass ordering.

Studying B1(12+)→B2(12+)ℓ+ℓ− semileptonic weak baryon decays with the SU(3) flavor symmetry

Motivated by recent anomalies in FCNC $b\to s\ell^+\ell^-$, we study $B_1\to B_2\ell^+\ell^-(\ell=e,\mu,\tau)$ semi-leptonic weak decays with the SU(3) flavor symmetry, where $B_{1,2}$ are the spin-1/2 baryons of single bottomed anti-triplet $T_{b3}$, single charmed anti-triplet $T_{c3}$ or light baryon octet $T_{8}$. Using the SU(3) irreducible representation approach, we first obtain the amplitude relations among different decays, and then predict the relevant not-yet measured observables of these decays. (a) We calculate the branching ratios of the $T_{b3}\to T_8 \mu^+\mu^-$ and $T_{b3}\to T_8 \tau^+\tau^-$ in the whole $q^2$ region and in the different $q^2$ bins by the measurement of $\Lambda^0_b\to \Lambda^0 \mu^+\mu^-$. Many of them are obtained for the first time. In addition, the longitudinal polarization fractions and the leptonic forward-backward asymmetries of all $T_{b3}\to T_{8}\ell^+\ell^-$ decays are very similar to each other in certain $q^2$ bin due to the SU(3) flavor symmetry. (b) We analyze the upper limits of $B(T_{c3}\to T_{8}\ell^+\ell^-)$ by using the experimental upper limits of $B(\Lambda^+_c\to p\mu^+\mu^-)$ and $B(\Lambda^+_c\to pe^+e^-)$, and find the experimental upper limit of $B(\Lambda^+_c\to p\mu^+\mu^-)$ giving effective bounds on the relevant SU(3) flavor symmetry parameters. The predictions of $B(\Xi^0_c \to \Xi^0e^+e^-)$ and $B(\Xi^0_c \to \Xi^0\mu^+\mu^-)$ will be different between the single-quark transition dominant contributions and the W-exchange dominant ones. (c) As for $T_{8}\to T'_8 \ell^+\ell^-$ decays, we analyze the single-quark transition contributions and the W-exchange contributions by using two measurements of $ B(\Xi^0\to \Lambda^0 e^+e^-)$ and $ B(\Sigma^+\to p\mu^+\mu^-)$, and give the branching ratio predictions by assuming either single-quark transition dominant contributions or the W-exchange dominant ones.

Bootstrapping Coulomb and Higgs branch operators

We apply the numerical conformal bootstrap to correlators of Coulomb and Higgs branch operators in 4d mathcal{N} = 2 superconformal theories. We start by revisiting previous results on single correlators of Coulomb branch operators. In particular, we present improved bounds on OPE coefficients for some selected Argyres-Douglas models, and compare them to recent work where the same cofficients were obtained in the limit of large r charge. There is solid agreement between all the approaches. The improved bounds can be used to extract an approximate spectrum of the Argyres-Douglas models, which can then be used as a guide in order to corner these theories to numerical islands in the space of conformal dimensions. When there is a flavor symmetry present, we complement the analysis by including mixed correlators of Coulomb branch operators and the moment map, a Higgs branch operator which sits in the same multiplet as the flavor current. After calculating the relevant superconformal blocks we apply the numerical machinery to the mixed system. We put general constraints on CFT data appearing in the new channels, with particular emphasis on the simplest Argyres-Douglas model with non-trivial flavor symmetry.

A roadmap to strange star

AbstractWhat if normal baryonic matter is compressed so tightly that atomic nuclei come into close contact? This question has been asked since 1930s. The first answer was presented by Lev Landau whose speculation has been developed, and the concept of neutron star is then popularized. However, another answer is related to strange star, which becomes worthy of attention especially after the establishment of the standard model of particle physics in 1960s. The basic ideas of this study are introduced pedagogically. We must point out emphatically that flavor symmetry and strong coupling between quarks would be essential in seeking true answer to the question. The final answer is expected to appear in the era of multimessenger astronomy. It is emphasized too that, besides the differences of global properties (e.g., mass‐radius relation, maximum mass, tidal deformability), the strong‐bound surface of strange star (rather than the gravity‐bound one for conventional neutron star) could play an important role in identifying a strange star by astronomical observations.