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)  μ⁢b, 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)  μ⁢b, 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.
Settore PHYS-01/A - Fisica sperimentale delle interazioni fondamentali e applicazioni
Settore IMIS-01/B - Misure elettriche ed elettroniche
   Comprehensive search for new phenomena in the dilepton spectrum at the LHC
   DITTO
   European Commission
   Horizon Europe Framework Programme
   101089007

   Turning noise into data: a discovery strategy for new weakly-interacting physics
   DISCOVERHEP
   European Commission
   Horizon 2020 Framework Programme
   948254
7-apr-2025
https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.134.142301
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2434/1158336
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