Leptoquark manoeuvres in the dark: a simultaneous solution of the dark matter problem and the $$ {R}_{D^{\left(\ast \right)}} $$ anomalies

Abstract

The measured branching fractions of B-mesons into leptonic final states derived by the LHCb, Belle and BaBar collaborations hint towards the breakdown of lepton flavour universality. In this work we take at face value the so-called $$ {R}_{D^{\left(\ast \right)}} $$ R D ∗ observables that are defined as the ratios of neutral B-meson charged-current decays into a D(*)-meson, a charged lepton and a neutrino final state in the tau and light lepton channels. A well-studied and simple solution to this charged current anomaly is to introduce a scalar leptoquark S1 that couples to the second and third generation of fermions. We investigate how S1 can also serve as a mediator between the Standard Model and a dark sector. We study this scenario in detail and estimate the constraints arising from collider searches for leptoquarks, collider searches for missing energy signals, direct detection experiments and the dark matter relic abundance. We stress that the production of a pair of leptoquarks that decays into different final states (i.e. the commonly called “mixed” channels) provides critical information for identifying the underlying dynamics, and we exemplify this by studying the tτbν and the resonant S1 plus missing energy channels. We find that direct detection data provides non-negligible constraints on the leptoquark coupling to the dark sector, which in turn affects the relic abundance. We also show that the correct relic abundance can not only arise via standard freeze-out, but also through conversion-driven freeze-out. We illustrate the rich phenomenology of the model with a few selected benchmark points, providing a broad stroke of the interesting connection between lepton flavour universality violation and dark matter.

Dark Matter abundance via thermal decays and leptoquark mediators

“…[6][7][8][9][10][11][12][13] and references therein). The possibility of DM coupled to leptoquarks has been considered before [14][15][16][17][18], but usually in combination with an additional Z 2 symmetry that forbids DM decay. Here we shall explore the minimal possibility that allows the mediator to simultaneously couple to DM-SM and pure SM currents.…”

Impact of Sommerfeld Effect and Bound State Formation in Simplified $t$-Channel Dark Matter Models

“…7. Just as in SD scattering, the parametric dependence to the Yukawa coupling for the SI DM-nucleon cross-section also scales 19 See also [58].…”

Anatomy of scalar mediated proton decays in $SO(10)$ models

“…Their non-trivial charges under the SM gauge symmetries and couplings with the SM quarks and leptons make them interesting from the phenomenological considerations. Potential new physics effects of many of these scalars have been explored in the context of the recent flavour anomalies (see for example, [11][12][13][14]), muon g − 2 anomaly [15][16][17], some events at the direct search experiments [18][19][20] and precision unification of gauge couplings in the absence of low energy supersymmetry [18,19,21]. All these require at least a few scalars at the sub GUT scale.…”