Abstract
A search for high-mass dielectron and dimuon resonances in the mass range of 250GeV to 6TeV is presented. The data were recorded by the ATLAS experiment in proton–proton collisions at a centre-of-mass energy of s=13TeV during Run 2 of the Large Hadron Collider and correspond to an integrated luminosity of 139 fb−1. A functional form is fitted to the dilepton invariant-mass distribution to model the contribution from background processes, and a generic signal shape is used to determine the significance of observed deviations from this background estimate. No significant deviation is observed and upper limits are placed at the 95% confidence level on the fiducial cross-section times branching ratio for various resonance width hypotheses. The derived limits are shown to be applicable to spin-0, spin-1 and spin-2 signal hypotheses. For a set of benchmark models, the limits are converted into lower limits on the resonance mass and reach 4.5TeV for the E6-motivated Zψ′ boson. Also presented are limits on Heavy Vector Triplet model couplings.
Highlights
Searches in the dilepton final state have a long and illustrious history with the discovery of the J /ψ meson in 1974 [1,2] and Υ meson in 1977 [3] as well as the Z boson in 1983 [4,5]. As these were key steps which led to the establishment of the Standard Model (SM) of particle physics, the study of the same final state could help to pave the way to a better understanding of the physics processes beyond it
Pythia v8.186, NNPDF23LO, EvtGen1.2.0 Pythia v8.210, NNPDF23LO, EvtGen1.2.0 Pythia v8.212, CTEQ6L1, EvtGen1.2.0 signal line shape described by a non-relativistic Breit–Wigner function convolved with the detector resolution, which simplifies reinterpretations of the result
The event with highest reconstructed mass is a dielectron candidate with mee = 4.06 TeV, formed of two electrons with ET = 2.01 TeV and ET = 1.92 TeV in the barrel region of the calorimeter
Summary
Searches in the dilepton (dielectron and dimuon) final state have a long and illustrious history with the discovery of the J /ψ meson in 1974 [1,2] and Υ meson in 1977 [3] as well as the Z boson in 1983 [4,5]. The majority of searches for new neutral high-mass resonances have focused on a new spin-1 vector boson, generally referred to as Z , that appears in models with extended gauge symmetries. In experimental terms the described scenarios would result in a local excess of signal candidates over a smoothly falling dilepton mass spectrum. This search has a clean experimental signature with a fully reconstructable final state and excellent detection efficiency. This Letter presents a search for a new resonance decaying into two electrons or two muons in 139 fb−1 of data collected in proto√n–proton (pp) collisions at the ergy s √= 13 TeV.
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