Abstract
We investigate scenarios with $\mathcal{O}(1\mathrm{\,TeV})$ scalar leptoquarks that act as portals between the Standard Model and Dark Matter. We assume that Dark Matter is a scalar singlet $S$ which couples to a scalar leptoquark $\Delta$ and the Higgs boson via the terms in the scalar potential. In addition, the leptoquark is endowed with Yukawa couplings to quarks and leptons that may address the anomalies in $B$ meson decays. We consider the $SS$ annihilation cross sections to estimate the Dark Matter relic abundance and explore the interplay between astrophysical, collider and flavour physics bounds on such models. In the heavy Dark Matter window, $m_S > m_\Delta$, the leptoquark portal becomes the dominant mechanism to explain the Dark Matter abundance. We find that the leptoquark Yukawa couplings, relevant for quark and lepton flavour physics, are decoupled from the dark matter phenomenology. By focussing on a scenario with a single leptoquark state, we find that relic density can only be explained when both $\Delta$ and $S$ masses are lighter than $\mathcal{O}(10\mathrm{\,TeV})$.
Highlights
Leptoquarks (LQs) are theoretically motivated hypothetical bosonic degrees of freedom that couple at tree-level to quark-lepton pairs [1,2]
We find that the leptoquark Yukawa couplings, relevant for quark and lepton flavor physics, are decoupled from the dark matter phenomenology
By comparing these upper bounds with Eq (38), we see that the limit on mΔ derived from dark matter (DM) relic abundance is more constraining than the ones derived from most flavor anomalies, with the only exception of RDðÃÞ, which is a treelevel process in the Standard Model (SM). If any of these anomalies is confirmed in the future, one could check from Eq (38) if the LQ scenario favored from flavor physics could be extended to accommodate DM via the mechanism discussed in this paper
Summary
Leptoquarks (LQs) are theoretically motivated hypothetical bosonic degrees of freedom that couple at tree-level to quark-lepton pairs [1,2] They naturally appear in theories unifying quarks and leptons [3,4] and composite Higgs models [5,6], and they provide a viable mechanism to explain neutrino masses [7,8]. Their interactions with fermions make them good candidates to address phenomenological problems in quark-lepton transitions, such as the discrepancies in B-meson decays observed at LHCb and the B factories [9], or to address discrepancies in chirality-suppressed observables, such as the anomalous magnetic moment of leptons [10,11,12].
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