Search for New Phenomena in Final States with Two Leptons and One or No b-Tagged Jets at √s=13  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 $\sqrt{s}=13\mathrm{TeV}$ by the ATLAS experiment at the LHC, corresponding to an integrated luminosity of $139{\mathrm{fb}}^{-1}$. 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 $g_{\ast }$, respectively. Contact interactions with $\Lambda /g_{\ast }$ 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.

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ATLAS Collaboration, Bawa, H. S., & Gao, Y. S. (2021). Search for new phenomena in final states with two leptons and one or no b-tagged jets at s=13 TeV using the ATLAS Detector. Physical Review Letters, 127(14), 141801. https://doi.org/10.1103/PhysRevLett.127.141801