Top-quark pair production is observed in lead–lead (Pb+Pb) collisions at √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 𝜎𝑡 ¯ 𝑡 =3.6 +1.0 −0.9(stat) +0.8 −0.5(syst) μb, 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 tt¯ Production in Pb+Pb Collisions at sNN=5.02 TeV with the ATLAS Detector / G. Aad, E.A.. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - 134:14(2025 Apr 07), pp. 142301.1-142301.22. [10.1103/physrevlett.134.142301]
Observation of tt¯ Production in Pb+Pb Collisions at sNN=5.02 TeV with the ATLAS Detector
A. Andreazza;A. Carbone;L. Carminati;S. D'Auria;L. Dell'Asta;M. Fanti;M. Lazzaroni;E. Mazzeo;C. Meroni;L. Nasella;F. Ragusa;A. Sala;R. Zanzottera;
2025
Abstract
Top-quark pair production is observed in lead–lead (Pb+Pb) collisions at √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 𝜎𝑡 ¯ 𝑡 =3.6 +1.0 −0.9(stat) +0.8 −0.5(syst) μb, 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.| File | Dimensione | Formato | |
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