Measurement of the top-quark mass using decays with a J/ψ meson at s = 13 TeV with the ATLAS detector

Journal article

The top-quark mass is measured using top-quark decays producing an isolated lepton and J/ψ meson reconstructed in its μ+μ− decay mode. The data sample was recorded with the ATLAS detector in proton-proton collisions at a centre-of-mass energy of s=13 TeV during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 140 fb−1. The measurement is based on the invariant mass m(ℓμ+μ−) of the system made of the isolated lepton ℓ from the W boson decay and the non-isolated μ+μ− pair from a J/ψ decay of a b-hadron, exploiting its sensitivity to the top-quark mass. An unbinned maximum-likelihood fit to the m(ℓμ+μ−) distribution is performed to extract the top-quark mass. The top-quark mass is measured to be mtop = 172.17 ± 0.80 (stat) ± 0.81 (syst) ± 1.07 (recoil) GeV, with a total uncertainty of 1.56 GeV. The third uncertainty arises from changing the dipole parton shower gluon-recoil scheme used in top-quark decays.

Authors: Aad, G; Aakvaag, E; Abbott, B; Abdelhameed, S; Abeling, K

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Springer
• Journal: Journal of High Energy Physics
• Volume: 2026
• Issue: 4
• Article number: 99
• Publication date: 2026-04-14
• Acceptance date: 2026-02-11
• DOI: 10.1007/jhep04(2026)099
• EISSN: 1029-8479
• ISSN: 1126-6708
• Language: English
• Keywords: Top Physics; Hadron-Hadron Scattering