Journal of High Energy Physics

, 2017:188 | Cite as

The role of the S 3 GUT leptoquark in flavor universality and collider searches

  • Ilja Doršner
  • Svjetlana Fajfer
  • Darius A. Faroughy
  • Nejc Košnik
Open Access
Regular Article - Theoretical Physics


We investigate the ability of the S 3 scalar leptoquark to address the recent hints of lepton universality violation in B meson decays. The S 3 leptoquark with quantum numbers \( \left(\overline{\mathbf{3}},\mathbf{3},1/3\right) \) naturally emerges in the context of an SU(5) GUT model without any conflict with the stringent limits from observed nucleon stability. Scalar leptoquark S 3 with left-handed couplings to 2nd and 3rd generations of charged leptons and down-type quarks seems well-suited to address both R K(∗) and R D(∗) . We quantify this suitability with numerical fits to a plethora of relevant flavor observables. The proposed SU(5) model calls for a second leptoquark state, i.e., \( {\tilde{R}}_2 \) with quantum numbers (3 , 2 , 1/6), if one is to generate gauge coupling unification and neutrino mass. We accordingly include it in our study to investigate \( {\tilde{R}}_2 \)’s ability to offset adverse effects of S 3 and thus improve a quality of numerical fits. A global fit of the leptoquark Yukawa couplings shows that large couplings of light S 3 to τ leptons are preferred. We furthermore identify \( B\to {K}^{\left(\ast \right)}\overline{\nu}\nu \) as the most sensitive channel to probe the preferred region of parameter space. Large couplings of S 3 to τ leptons are finally confronted with the experimental searches for τ final states at the Large Hadron Collider. These searches comprise a study of decay products of the leptoquark pair production, as well as, and more importantly, an analysis of the high-mass ττ finalstates.


Beyond Standard Model GUT Heavy Quark Physics Kaon Physics 


Open Access

This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited.


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© The Author(s) 2017

Authors and Affiliations

  1. 1.Faculty of Electrical Engineering, Mechanical Engineering and Naval Architecture (FESB)University of SplitSplitCroatia
  2. 2.Department of PhysicsUniversity of LjubljanaLjubljanaSlovenia
  3. 3.J. Stefan InstituteLjubljanaSlovenia

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