Simplified models of flavourful leptoquarks

Abstract

We study the implications of single leptoquark extensions of the Standard Model (SM) under the assumption that their enhanced Yukawa sectors are invariant under global Abelian flavour symmetries already present in SM mass terms. Such symmetries, assumed to be the 'residual' subgroups of an ultra-violet flavour theory, have previously been considered in order to predict fermionic mixing angles. Here we focus instead on their effect on the novel flavour structures sourced by the leptoquark representations that address the present R K ( ) anomalies in semileptonic rare B-decays. Combined with existing flavour data, the residual symmetries prove to be extremely constraining; we find that the (quark-lepton) leptoquark Yukawa couplings fall within O(10) highly predictive patterns, each with only a single free parameter, when 'normal' (SM-like) hierarchies are assumed. In addition, proton decay for the scalar SU(2) triplet representation is naturally avoided in the residual symmetry approach without relying on further model building. Our results indicate that a simultaneous explanation for the R K ( ) anomalies and the flavour puzzle may be achieved in a simplified, model-independent formalism.

Low-energy phenomenology of scalar leptoquarks at one-loop accuracy

“…The S 1 leptoquark has been considered as possible mediator for all anomalies [32][33][34][35][36][37][38][39][40][41], with varying degree of success. S 3 , instead, has long been recognized to be a very good candidate to address the deviations in the b → sµµ transition [42][43][44][45][46][47][48][49]. Finally, the combination of both leptoquarks has been considered as a good combined explanation of charged and neutral-current B-anomalies [50,51] and possible ultraviolet (UV) completions have been proposed in terms of a composite Higgs model [52], combining flavour anomalies with a solution to the Higgs hierarchy problem, as well as in the framework of asymptotically safe quantum gravity [53].…”

R2 as a single leptoquark solution to RD(*Попов1, Schmidt2, White3 2019Phys. Rev. D701430View full textAdd to dashboardCite

“…The most common explanation for these anomalies is to extend the SM by leptoquarks (see Refs. [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] for a leptoquark solution to the R K ðÃÞ anomalies, Refs. [34,[39][40][41][42][43][44][45] for the R D ðÃÞ anomalies and Refs.…”

Flavor phenomenology of the leptoquark singlet-triplet model

“…Once more, LQs are prime candidates for an explanation. Despite the U 1 vector LQ SU(2) L singlet [69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86] and scalar LQ S 2 option [41,[87][88][89][90][91][92][93][94][95], the scalar LQ Φ 1 [36,40,50,74,89,[96][97][98][99][100][101][102][103][104][105][106][107][108][109][110] or the combination of Φ 1 and Φ 3 , 4 can explain these data [49,74,…”