Top-quark pair production is observed in lead-lead (Pb+Pb) collisions at sqrt(sNN)=5.02 TeV at the Large Hadron Collider with the ATLAS detector. The data sample was recorded in 2015 and 2018, amounting to an integrated luminosity of 1.9 nb-1. Events with exactly one electron and one muon and at least two jets are selected. Top-quark pair production is measured with an observed (expected) significance of 5.0 (4.1) standard deviations. The measured top-quark pair production cross section is sigma_ttbar = 3.6 +1.0-0.9(stat) +0.8-0.5(syst) mub, with a total relative uncertainty of 31%, and is consistent with theoretical predictions using a range of different nuclear parton distribution functions. The observation of this process consolidates the evidence of the existence of all quark flavors in the preequilibrium stage of the quark-gluon plasma at very high energy densities, similar to the conditions present in the early Universe.
Observation of ttbar Production in Pb+Pb Collisions at sqrt(sNN) = 5.02 TeV with the ATLAS Detector
G Chiodini;Francesco De Santis;E Gorini;S Grancagnolo;FG Gravili;A Palazzo;M Primavera;S Spagnolo;A Ventura;
2025-01-01
Abstract
Top-quark pair production is observed in lead-lead (Pb+Pb) collisions at sqrt(sNN)=5.02 TeV at the Large Hadron Collider with the ATLAS detector. The data sample was recorded in 2015 and 2018, amounting to an integrated luminosity of 1.9 nb-1. Events with exactly one electron and one muon and at least two jets are selected. Top-quark pair production is measured with an observed (expected) significance of 5.0 (4.1) standard deviations. The measured top-quark pair production cross section is sigma_ttbar = 3.6 +1.0-0.9(stat) +0.8-0.5(syst) mub, with a total relative uncertainty of 31%, and is consistent with theoretical predictions using a range of different nuclear parton distribution functions. The observation of this process consolidates the evidence of the existence of all quark flavors in the preequilibrium stage of the quark-gluon plasma at very high energy densities, similar to the conditions present in the early Universe.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
