Abstract
Models with massive vector leptoquarks, resulting from an $SU(4)$ gauge symmetry spontaneously broken at the TeV scale, are of great phenomenological interest given the current "anomalies" in semileptonic $B$ decays. We analyze the relations between low- and high-energy observables in such class of models to next-to-leading order accuracy in the $SU(4)$ gauge coupling $g_4$. For large values of $g_4$, motivated by recent $B$-physics data, one-loop corrections are sizeable. The main effect is an enhanced contribution at low-energy, at fixed on-shell couplings. This result has important implications for current and future high-energy searches of vector leptoquark models.
Highlights
A natural expectation of grand-unified theories, where a single fermion representation contains both quark and lepton fields, is the presence of massive vector leptoquarks, i.e., vector fields transforming quarks into leptons and vice versa
One of the most appealing constructions of this type is the model proposed by Pati and Salam (PS) [1], where quarks and leptons are unified in fundamental representations of the SUð4Þ gauge group
A renewed phenomenological interest in the PS model has been triggered by the recent B-physics anomalies, i.e., the hints of lepton flavor universality violations in semileptonic B decays [2,3,4,5,6,7]
Summary
A natural expectation of grand-unified theories, where a single fermion representation contains both quark and lepton fields, is the presence of massive vector leptoquarks, i.e., vector fields transforming quarks into leptons and vice versa. The proposed models have a few differences, but the TeV-scale dynamics is always characterized by the gauge group SUð4Þ× SUð3Þ × SUð2Þ × Uð1Þ, effectively acting in a family nonuniversal way These models, which we collectively denote as 4321 models, provide both a successful ultraviolet (UV) completion for effective descriptions of the B-physics anomalies and, at the same time, represent a first step to shed light on the origin of SM mass hierarchies [13] (alternative approaches to embed the U1 in extended PS-type models have been proposed in [17,18]). Heavy-vector dynamics, we present, for the first time, an estimate of the NLO corrections associated to the leptoquark coupling (g4) Since the latter is large, we work in the limit where all SM couplings (both gauge and Yukawa) are set to zero. We evaluate NLO corrections to low-energy amplitudes in terms of these parameters to perform the matching to the Standard Model Effective Theory (SMEFT)
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