Model for the singlet-triplet leptoquarks
Leandro Da Rold, Federico Lamagna
Abstract
The deviations of $B$-meson decays measured in ${R}_{{D}^{(*)}}^{\ensuremath{\tau}\ensuremath{\ell}}$ and ${R}_{{K}^{(*)}}^{\ensuremath{\mu}e}$ can be explained by the presence of two scalar leptoquarks, a singlet ${S}_{1}$ and a triplet ${S}_{3}$, mostly coupled to the third generation. We consider a theory of resonances, as an effective description of a strongly interacting theory, that generates the leptoquarks and the Higgs as Nambu-Goldstone bosons, with the rest of the resonances at a scale of order 10--30 TeV. We assume anarchic partial compositeness for the flavor of the SM fermions. Under this hypothesis, we study whether it is possible to reproduce the deviations in the $B$ decays without being in conflict with flavor and electroweak bounds. We find a tension between ${R}_{{D}^{(*)}}^{\ensuremath{\tau}\ensuremath{\ell}}$ and some flavor observables, dominated by flavor violating $\ensuremath{\tau}$ decays and $\mathrm{\ensuremath{\Delta}}{m}_{{B}_{s}}$, that require a tuning of order 10%--25%. We also compute the potential of the scalars showing that leptoquarks with masses $O(2--3)\text{ }\text{ }\mathrm{TeV}$ can be naturally expected in the model. We discuss briefly the phenomenology of the other resonances.