Search for quantum black hole production in $\mathrm{lepton}+\text{jet}$ final states using proton-proton collisions at $\sqrt{s}=13\text{}\text{}\mathrm{TeV}$ with the ATLAS detector

A search for quantum black holes in $\mathrm{electron}+\text{jet}$ and $\mathrm{muon}+\text{jet}$ invariant mass spectra is performed with $140\text{}\text{}{\mathrm{fb}}^{-1}$ of data collected by the ATLAS detector in proton-proton collisions at $\sqrt{s}=13\text{}\text{}\mathrm{TeV}$ at the Large Hadron Collider. The observed invariant mass spectrum of $\mathrm{lepton}+\text{jet}$ pairs is consistent with Standard Model expectations. Upper limits are set at 95% confidence level on the production cross section times branching fractions for quantum black holes decaying into a lepton and a quark in a search region with invariant mass above 2.0 TeV. The resulting quantum black hole lower mass threshold limit is 9.2 TeV in the Arkani-Hamed-Dimopoulos-Dvali model, and 6.8 TeV in the Randall-Sundrum model.