Explaining dark matter and B decay anomalies with an Lμ - Lτ model

We present a dark sector model based on gauging the L-mu - L-tau symmetry that addresses anomalies in b -> s mu(+) mu(-) decays and that features a particle dark matter candidate. The dark matter particle candidate is a vector-like Dirac fermion coupled to the Z' gauge boson of the L-mu - L-tau symmetry. We compute the dark matter thermal relic density, its pair-annihilation cross section, and the loop-suppressed dark matter-nucleon scattering cross section, and compare our predictions with current and future experimental results. We demonstrate that after taking into account bounds from B-s meson oscillations, dark matter direct detection, and the CMB, the model is highly predictive: B physics anomalies and a viable particle dark matter candidate, with a mass of similar to (5 - 23) GeV, can be accommodated only in a tightly constrained region of parameter space, with sharp predictions for future experimental tests. The viable region of parameter space expands if the dark matter is allowed to have L-mu - L-tau charges that are smaller than those of the SM leptons.