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Flavor Anomalies, the Diphoton Excess and a Dark Matter Candidate

We argue that the diphoton excess recently reported by ATLAS and CMS can be explained, along with several anomalies seen in the flavor sector, in models where a Standard-Model singlet scalar resonance with mass $M \approx 750$ GeV is produced in gluon fusion via loops containing a scalar color- triplet leptoquark $ϕ$. For a leptoquark mass $M_ϕ\lesssim$ 1 TeV, the production cross section is naturally in the 10 fb range. A large $S \to γγ$ branching ratio can be obtained by coupling the scalar S to new color-singlet fermions $χ$ with electroweak scale masses, which can be part of an $SU(2)_L$ multiplet, whose neutral component has the right mass and quantum numbers to be a dark matter candidate. Our model reveals a connection between flavor anomalies, the nature of dark matter and a new scalar, which acts as a mediator to the dark sector. The loop-mediated decay $S \to τ^+τ^-$ could be a striking signature of this model.