TY  - RPRT
TI  - Search for narrow low-mass resonances in the four-muon final state with the ATLAS detector at the LHC
IS  - ATLAS-CONF-2023-041
M1  - PUBDB-2023-07321
M1  - ATLAS-CONF-2023-041
SP  - 21
PY  - 2023
N1  - Preliminary results. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLAS-CONF-2023-041. The authors list may be incomplete!
AB  - A search for new low-mass resonances in the four-muon final state in the four-muon invariant mass range from 10−50 GeV is performed using pp collision data recorded with the ATLAS detector at the Large Hadron Collider. The data correspond to an integrated luminosity of 20.3 fb<sup>−1</sup> at a centre-of-mass energy (√s) of 8T eV collected in 2012, and 51.5 fb<sup>−1</sup> and 58.5 fb<sup>−1</sup> collected at √s=13 TeV in 2015-2017 and 2018, respectively. An excess at 18 GeV in the invariant mass spectrum of the four-muon system of the selected Υ(1S)+μ<sup>+</sup>μ<sup>−</sup>→μ<sup>+</sup>μ<sup>−</sup> μ<sup>+</sup>μ<sup>−</sup> final state is observed in the 8 TeV data. Although not blinded, typical selection criteria are used and variations studied to explore the stability of the excess, resulting in local significances of the excess of between be 3.6 σ and 6.3 σ corresponding to global significances of 1.9 σ to 5.4 σ. A baseline choice of selection cuts defined for the analysis at 8 TeV was defined in the 8 TeV data to be further probed at Run 2. Subsequent analysis of 13 TeV data finds a smaller excess at the same four-muon invariant mass with a significance of 1.9 σ in early 13 TeV data runs, while data collected with more restrictive trigger selections in the 2018 dataset finds no evidence of a signal. LHCb and CMS have observed no excess at this mass. Signal MC and di-Υ(1S) production studies in data are used to quantify performance across the three data-taking periods, finding reductions in expected sensitivity in the 13 TeV dataset compared to that at 8 TeV. The lack of observation of a signal in the 13 TeV is assessed to be in tension with the structure observed at an invariant mass of 18 GeV in the 8 TeV dataset, up to a maximum of 2.7σ. We subsequently set and report limits on the total production cross section times branching fraction to a four-muon final state for a new state at a mass of 18 GeV for a variety of models.
KW  - four-muon (autogen)
KW  - resonance (autogen)
KW  - Upsilon+mumu (autogen)
KW  - BPHYS (autogen)
LB  - PUB:(DE-HGF)29
DO  - DOI:10.3204/PUBDB-2023-07321
UR  - https://bib-pubdb1.desy.de/record/599325
ER  -