We present a three-site Pati-Salam gauge model able to explain the Standard Model flavor hierarchies while, at the same time, accommodating the recent experimental hints of lepton-flavor non-universality in B decays. The model is consistent with low-and high-energy bounds, and predicts a rich spectrum of new states at the TeV scale that could be probed in the near future by the high-pT experiments at the LHC.

We present a thorough investigation of the vector leptoquark hypothesis for a combined explanation of the B-physics anomalies. We analyze this hypothesis from a twofold perspective, taking into account recent results from B-physics observables and high-p T searches. First, using a simplified model, we determine the general conditions for a successful lowenergy fit in presence of right-handed leptoquark couplings (neglected in previous analyses). Second, we show how these conditions, in particular a sizable 2-3 family mixing, can be achieved in a motivated ultraviolet completion. Our analysis reinforces the phenomenological success of the vector leptoquark hypothesis in addressing the anomalies, and its compatibility with motivated extensions of the Standard Model based on the idea of flavor non-universal gauge interactions. The implications of right-handed leptoquark couplings for a series of key low-energy observables, namely B s → τ τ and τ → µ lepton flavor violating processes, both in τ and in B decays, are discussed in detail. The role of the ultraviolet completion in precisely estimating other low-energy observables, most notably ∆F = 2 amplitudes, is also addressed. also [32,37]).We provide a detailed implementation of the U 1 leptoquark in a renormalizable model based on the (flavor non-universal) gauge group SU (4) 3 × SU (3) 1+2 × SU (2) L × U (1) , which in turn can be embedded in PS 3 [31]. In this context, we complement the simplified-model analysis by including oneloop contributions to low-energy observables (most notably ∆F = 2 amplitudes and dipole operators) which can be reliably computed only within a UV-complete framework.The paper is organized as follows. In Section 2 we present the simplified-model analysis: we introduce the Lagrangian describing the U 1 couplings to SM fermions, and analyze its low-energy limit. We discuss all the observables insensitive to the UV completion (Section 2.2), which are later used to fit low-energy data (Section 2.3). We finally comment on the high-p T constraints (Section 2.4).The UV-complete model is presented and discussed in Section 3: on the model-building side we pay particular attention to the flavor structure of the model (Section 3.2); on the phenomenological side we present complete expressions for the UV-dependent (loop-induced) observables, which were omitted in the low-energy fit (Section 3.3). The results are summarized in Section 4.

The three-site Pati-Salam gauge model provides a consistent description for the hints of lepton-flavor non-universality observed in B decays, connecting the present pattern of "anomalies" to the origin of the Standard Model Yukawa couplings. We present here a detailed analysis of the model predictions for a series of low-energy observables, mainly in B and τ physics. The model is in good agreement with present data and predicts a well-defined pattern of non-standard effects in lowenergy observables that could allow us to test it in the near future. Particularly interesting are the predictions of large τ → µ Lepton Flavor Violating processes, such as τ → µγ, τ → 3µ, B → Kτ µ, and B s → τ µ. Also µ → 3e, µ → eγ, and K L → µe decays could be not far from the present exclusion bounds, although this conclusion is more model dependent.

We examine the low-energy signatures of axion-like particles (ALPs) in lepton flavor violating (LFV) processes. By using a dimension-5 effective Lagrangian, we compute the most general ALP contributions to LFV decays of leptons and mesons. The provided expressions are valid for any choice of ALP mass and couplings. We explore the complementarity of different processes, identifying specific patterns to be experimentally tested. Constraints on LFV couplings are derived from existing data and prospects for forthcoming experiments are also discussed. As a by-product, we revisit the possibility of a simultaneous explanation of the observed discrepancies in the muon and electron g − 2 through ALP interactions.