Broken Flavor Symmetry Research Articles

Flavour alignment of New Physics in light of the (g − 2)μ anomaly

We investigate the flavour alignment conditions that New Physics (NP) models need to satisfy in order to address the (g − 2)μ anomaly and, at the same time, be consistent with the tight bounds from μ → eγ and τ → μγ. We analyse the problem in general terms within the SMEFT, considering the renormalisation group evolution of all the operators involved. We show that semileptonic four-fermion operators, which are likely to generate a sizeable contribution to the (g − 2)μ anomaly, need to be tightly aligned to the lepton Yukawa couplings and the dipole operators in flavour space. While this tuning can be achieved in specific NP constructions, employing particular dynamical assumptions and/or flavour symmetry hypotheses, it is problematic in a wide class of models with broken flavour symmetries, such as those proposed to address both charged- and neutral-current B anomalies. We quantify this tension both in general terms, and in the context of explicit NP constructions.

Higgs boson physics and broken flavor symmetry – LHC phenomenology

The LHC implications are presented of a simplified model of broken flavor symmetry in which a new scalar (a flavon) emerges with mass in the TeV range. We summarize the influence of the model on Higgs boson physics, notably on the production cross section and decay branching fractions. Limits are obtained on the flavon ϕ from heavy Higgs boson searches at the LHC at 7 and 8 TeV. The branching fractions of the flavon are computed as a function of the flavon mass and the Higgs-flavon mixing angle. We explore possible discovery of the flavon at 14 TeV, particularly via the ϕ→Z0Z0 decay channel in the 2ℓ2ℓ′ final state, and through standard model Higgs boson pair production ϕ→hh in the bb‾γγ final state. The flavon mass range up to 500 GeV could probed down to quite small values of the Higgs-flavon mixing angle with 100 fb−1 of integrated luminosity at 14 TeV.

Up quark masses from down quark masses

The quark and charged lepton masses and the angles and phase of the CKM mixing matrix are nicely reproduced in a model which assumes SU ( 3 ) ⊗ SU ( 3 ) flavor symmetry broken by the v.e.v.'s of fields in its bi-fundamental representation. The relations among the quark mass eigenvalues, m u / m c ≈ m c / m t ≈ m d 2 / m s 2 ≈ m s 2 / m b 2 ≈ Λ GUT 2 / M Pl 2 , follow from the broken flavor symmetry. Large tan β is required which also provides the best fits to data for the obtained textures. Lepton–quark grandunification with a field that breaks both SU ( 5 ) and the flavor group correctly extends the predictions to the charged lepton masses. The seesaw extension of the model to the neutrino sector predicts a Majorana mass matrix quadratically hierarchical as compared to the neutrino Dirac mass matrix, naturally yielding large mixings and low mass hierarchy for neutrinos.

Enhanced worldvolume supersymmetry and intersecting domain walls inN=1supersymmetric QCD

We study the worldvolume dynamics of $1/2$-supersymmetric domain walls in $\mathcal{N}=1$ supersymmetric QCD with ${N}_{f}=N$ flavors, and exhibit an enhancement of supersymmetry for the reduced moduli space associated with broken flavor symmetries. We provide an explicit construction of the worldvolume superalgebra which corresponds to an $\mathcal{N}=2$ K\"ahler sigma model in $2+1\mathrm{D}$ deformed by a potential, given by the norm squared of a U(1) Killing vector, resulting from the flavor symmetries broken by unequal quark masses. This framework leads to a worldvolume description of novel two-wall-junction configurations, which are $1/4$-supersymmetric objects, but nonetheless preserve two supercharges when viewed as kinks on the wall worldvolume.

Supersymmetry breaking and the SUSY flavour problem

Nonuniversality in the soft breaking terms is a generic feature in softly broken Supersymmetry. In particular, we show here that trilinear couplings are always nonuniversal in a theory that explains the Yukawa hierarchy in the frame of a spontaneously broken flavour symmetry. We analyse the constraints from low energy experiments and we find that large SUSY contributions are expected in the μ → eγ transition in the near future with SUSY masses around the TeV scale.

Microscopic correlations for non-Hermitian Dirac operators in three-dimensional QCD

In the presence of a nonvanishing chemical potential the eigenvalues of the Dirac operator become complex. We calculate spectral correlation functions of complex eigenvalues using a random matrix model approach. Our results apply to non-Hermitian Dirac operators in three-dimensional QCD with broken flavor symmetry and in four-dimensional QCD in the bulk of the spectrum. The derivation follows earlier results of Fyodorov, Khoruzhenko, and Sommers for complex spectra exploiting the existence of orthogonal polynomials in the complex plane. Explicit analytic expressions are given for all microscopic k-point correlation functions in the presence of an arbitrary even number of massive quarks, both in the limit of strong and weak non-Hermiticity. In the latter case the parameter governing the non-Hermiticity of the Dirac matrices is identified with the influence of the chemical potential.

Heavy quark condensates from dynamically broken flavour symmetry

We study the dynamics of top quark condensation induced by gauge interactions resulting from a broken flavour symmetry. The gap equation in dressed ladder approximation is solved numerically to obtain directly the top quark mass. The new high energy dynamics reduces the prediction of m t somewhat, but the usual problems of m t being too large and fine tuning remain. In order to solve these problems we extend our discussion to include fourth generation quark condensates.

Constraints on dynamical flavor symmetry breaking in quantum chromodynamics: Vafa-Witten theorem

We examine the Dyson-Schwinger equation for the quark propagator in quantum chromodynamics by employing the gauge technique with the object of investigating spontaneously broken flavor symmetry in the chiral limit of vanishing current quark masses. We show that dynamical breakdown of flavorSU V (N F ) symmetry does not occur, thus reiterating an assertion by Vafa and Witten. Our analysis is limited to three flavors but is generalizable to an arbitrary number of flavors,N F>3.

Effective theories with broken flavor symmetry

We generalize the work of Ovrut and Schnitzer on effective theories derived from a non-Abelian gauge theory to include the physically interesting case of broken flavor symmetry. Our calculations are performed at the one-loop level. We show that at an intermediate stage in the calculations two distinct renormalized gauge coupling constants appear, one describing gauge field coupling to heavy particles and the other describing coupling to light particles. Appropriately modified Slavnov-Taylor identities are shown to hold. We also consider a simple alternative to the Ovrut-Schnitzer rules for calculating with effective theories.