Search for boosted low-mass resonances decaying into hadrons produced in association with a photon in pp collisions at $\sqrt{s}=$13 TeV with the ATLAS detector

Abstract

Many extensions of the Standard Model, including those with dark matter particles, propose new mediator particles that decay into hadrons. This paper presents a search for such low mass narrow resonances decaying into hadrons using 140 fb${}^{-1}$ of proton-proton collision data recorded with the ATLAS detector at a centre-of-mass energy of 13 TeV. The resonances are searched for in the invariant mass spectrum of large-radius jets with two-pronged substructure that are recoiling against an energetic photon from initial state radiation, which is used as a trigger to circumvent limitations on the maximum data recording rate. This technique enables the search for boosted hadronically decaying resonances in the mass range 20-100 GeV hitherto unprobed by the ATLAS Collaboration. The observed data are found to agree with Standard Model predictions and 95% confidence level upper limits are set on the coupling of a hypothetical new spin-1 $Z^{\prime }$ resonance with Standard Model quarks as a function of the assumed $Z^{\prime }$-boson mass in the range between 20 and 200 GeV.

38 pages in total, author list starting page 21, 5 figures, 0 tables, published on JHEP. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EXOT-2022-33