The story of the b → s l⁺ l^- anomalies

Ten years ago, the LHCb collaboration first reported deviations between their measurements and Standard-Model predictions of the B → K* μ⁺ μ^- decay distribution. This rare process, which involves the quark-level transition b → s μ⁺ μ^-, is expected to be highly sensitive to possible beyond-the-SM effects, and the observed differences have created substantial excitement. The last ten years have seen improved measurements of B → K* μ⁺ μ^- and several related processes, as well as improved theory predictions, many of which involve lattice-QCD computations. While hints for violation of muon-versus-electron flavor universality have disappeared in 2022, the anomalies in the absolute decay rates and angular observables persist, and consistently point to a shift away from the Standard-Model value in one of the Wilson coefficients that appears in the effective-field-theory description of this class of processes. Improving our understanding of the nonperturbative QCD contributions will be essential in answering the question whether this shift is indeed due to new fundamental physics.