The $B$ Anomalies, the $U_1$ Leptoquark and Dark Matter

TL;DR

This paper explores how a vector leptoquark $U_1$ can explain B-anomalies and examines the implications of a scalar dark matter candidate coupling to both the Higgs and the leptoquark, updating viability constraints.

Contribution

It introduces a model where dark matter couples to a $U_1$ leptoquark, analyzing its effects on dark matter observables and updating the parameter space viability.

Findings

$U_1$ leptoquark explains B-anomalies with mass ≥ 1.8 TeV.

Scalar dark matter viability is limited to masses ≥ 1.6 TeV.

Dark matter constraints are relaxed when coupling to $U_1$ is included.

Abstract

The present-day $B$-anomalies involving $b \to s \mu^+ \mu^-$ or $b \to c \tau^- {\bar\nu}$ transitions can all be explained with the addition of a vector $U_1$ leptoquark with a mass of $M_{U_1} \ge 1.8$ TeV. In the scalar singlet dark matter model (SSDMM), the DM is a scalar $S$ that couples to the Higgs via $\lambda_{hS} \, S^2|H|^2$. We update the fit to the data and find that the SSDMM is now viable only for $M_S \ge 1.6$ TeV. In this paper, we assume that the DM also couples to the $U_1$ via $\lambda_{U_1 S} \, S^2 \, U_{1\mu}^{\dagger} U^{\mu}_1$. In addition to leading to DM annihilation via $S S \to U_1 {\bar U}_1$, this coupling generates $SSgg$ and $SS\gamma\gamma$ couplings at one loop. Although naively divergent, these loop diagrams can be calculated under the assumption that the $U_1$ is a gauge boson of a group broken at the TeV scale. With this DM-$U_1$ coupling term, there are additional contributions to the various DM observables (relic density, direct and indirect detection). We find that the constraints on the SSDMM are relaxed for both heavy DM ($M_S \ge M_{U_1}$) and light DM ($M_S < M_{U_1}$).