Search for New Phenomena in Final States with Two Leptons and One or No $b$-Tagged Jets at $\sqrt{s}=13\text{}\text{}\mathrm{TeV}$ Using the ATLAS Detector

A search for new phenomena is presented in final states with two leptons and one or no $b$-tagged jets. The event selection requires the two leptons to have opposite charge, the same flavor (electrons or muons), and a large invariant mass. The analysis is based on the full run-2 proton-proton collision dataset recorded at a center-of-mass energy of $\sqrt{s}=13\text{}\text{}\mathrm{TeV}$ by the ATLAS experiment at the LHC, corresponding to an integrated luminosity of $139\text{}\text{}{\mathrm{fb}}^{-1}$. No significant deviation from the expected background is observed in the data. Inspired by the $B$-meson decay anomalies, a four-fermion contact interaction between two quarks ($b$, $s$) and two leptons ($ee$ or $\mu \mu $) is used as a benchmark signal model, which is characterized by the energy scale and coupling, $\Lambda $ and ${g}_{*}$, respectively. Contact interactions with $\Lambda /{g}_{*}$ lower than 2.0 (2.4) TeV are excluded for electrons (muons) at the 95% confidence level, still far below the value that is favored by the $B$-meson decay anomalies. Model-independent limits are set as a function of the minimum dilepton invariant mass, which allow the results to be reinterpreted in various signal scenarios.