Search

Abstract We study two-site deconstructions of the SU(2) L gauge group factor of the SM. Models based on this approach can explain the hierarchies of the quark masses and CKM mixing between third and light families if these fields are localised on different sites by the presence of hierarchical new physics scales. The model leads to an accidental global U(2) q × U(3) u × U(3) d flavour symmetry which prevents dangerously large effects in flavour observables, making a TeV extension of the SM possible. Given the structure of the PMNS matrix in the neutrino sector, we explore different possibilities for the arrangement of the leptons on the two sites, and consider different models with U(2) ℓ or U(3) ℓ flavour symmetries. The phenomenology of the models is mostly governed by a massive vector triplet of SU(2) L . We study the interesting interplay between LHC searches and precision observables. In particular, one of the models can give a sizeable lepton flavour universal effect in the Wilson coefficient C 9 while naturally suppressing contributions to C 10, as suggested by current b → sℓ + ℓ − data, predicting simultaneously a mild positive shift in the W boson mass. more...

Abstract Flavor deconstruction refers to ultraviolet completions of the Standard Model where the gauge group is split into multiple factors under which fermions transform non-universally. We propose a mechanism for charging same-family fermions into different factors of a deconstructed gauge theory in a way that gauge anomalies are avoided. The mechanism relies in the inclusion of a strongly-coupled sector, responsible of both anomaly cancellation and the breaking of the non-universal gauge symmetry. As an application, we propose different flavor deconstructions of the Standard Model that, instead of complete families, uniquely identify specific third-family fermions. All these deconstructions allow for a new physics scale that can be as low as few TeV and provide an excellent starting point for the explanation of the Standard Model flavor hierarchies. more...

Abstract We present a model based on S 1 scalar leptoquarks to solve the tension observed in the recently proposed non-leptonic optimized observables L K ∗ K ¯ ∗ $$ {L}_{K^{\ast }{\overline{K}}^{\ast }} $$ and L K K ¯ $$ {L}_{K\overline{K}} $$ . These observables are constructed as ratios of U-spin related decays based on B d , s 0 → K ∗ 0 K ¯ ∗ 0 $$ {B}_{d,s}^0\to {K}^{\left(\ast \right)0}{\overline{K}}^{\left(\ast \right)0} $$ . The model gives a one-loop contribution to the Wilson coefficient of the chromomagnetic dipole operator needed to explain the tension in both non-leptonic observables, while naturally avoiding large contributions to the corresponding electromagnetic dipoles. The necessary chiral enhancement comes from an O(1) Yukawa coupling with a TeV-scale right-handed neutrino running in the loop. We endow the model with a U(2) flavor symmetry, necessary to protect light-family flavor observables that otherwise would be in tension. Furthermore, we show that the same S 1 scalar leptoquark is capable of simultaneously explaining the hints of lepton flavor universality violation observed in charged-current B-decays. The model therefore provides a potential link between two puzzles in B-physics and TeV-scale neutrino mass generation. Finally, the combined explanation of the B-physics puzzles unavoidably results in an enhancement of B B → Kν ν ¯ $$ \mathcal{B}\left(B\to K\nu \overline{\nu}\right) $$ , yielding a value close to present bounds. more...

Abstract We analyze the compatibility of the hypothesis of third-family quark-lepton unification at the TeV scale with electroweak precision data, lepton flavor universality tests, and high-p T constraints. We work within the framework of the UV complete flavor non-universal 4321 gauge model, which is matched at one loop to the Standard Model Effective Field Theory. For consistency, all electroweak precision observables are also computed at one loop within the effective field theory. At tree level, the most sizeable corrections are to W → τν τ and Z → ν τ ν τ due to integrating out a pseudo-Dirac singlet fermion required by the model for neutrino mass generation. At loop level, the new colored states of the model generate large flavor-universal contributions to the electroweak precision observables via leading- and next-to-leading log running effects, yielding a significant improvement in the electroweak fit (including an increase in the W-boson mass). These effects cannot be decoupled if the model addresses the charged-current B-meson anomalies. Overall, we find good compatibility between the data sets, while simultaneously satisfying all low- and high-energy constraints. more...

We analyze K→πνν¯ rates in a model with a TeV-scale leptoquark addressing B-meson anomalies, based on the flavor non-universal 4321 gauge group featuring third-generation quark-lepton unification. We show that, together with the tight bounds imposed by ΔF=2 amplitudes, the present measurement of B(K+→π+νν¯) already provides a non-trivial constraint on the model parameter space. In the minimal version of the model, the deviations from the Standard Model in B(K+→π+νν¯) are predicted to be in close correlation with non-standard effects in the Lepton Flavor Universality ratios RD and RD⁎. With the help of future data, these correlations can provide a decisive test of the model. more...

The recent B-meson anomalies are coherently explained at the TeV scale by 4321 gauge models with hierarchical couplings reminiscent of the Standard Model Yukawas. We show that such models arise as the low-energy limit of a complete theory of flavor, based on a warped fifth dimension where each Standard Model family is quasi-localized on a different brane. The Higgs is identified as a pseudo-Nambu-Goldstone boson emerging from the same dynamics responsible for 4321 symmetry breaking. This novel construction unifies quarks and leptons in a flavor non-universal manner, provides a natural description of flavor hierarchies, and addresses the electroweak hierarchy problem. more...