Azimuthal Angle Correlations of Muons Produced via Heavy-Flavor Decays in 5.02 TeV Pb+Pb and pp Collisions with the ATLAS Detector

UNSPECIFIED (2024) Azimuthal Angle Correlations of Muons Produced via Heavy-Flavor Decays in 5.02 TeV Pb+Pb and pp Collisions with the ATLAS Detector. Physical review letters, 132 (20): 202301. ISSN 1079-7114

Abstract

Angular correlations between heavy quarks provide a unique probe of the quark-gluon plasma created in ultrarelativistic heavy-ion collisions. Results are presented of a measurement of the azimuthal angle correlations between muons originating from semileptonic decays of heavy quarks produced in 5.02 TeV Pb+Pb and ⁢ collisions at the LHC. The muons are measured with transverse momenta and pseudorapidities satisfying T>4  GeV and ||<2.4, respectively. The distributions of azimuthal angle separation Δ⁢ for muon pairs having pseudorapidity separation |Δ⁢|>0.8, are measured in different Pb+Pb centrality intervals and compared to the same distribution measured in ⁢ collisions at the same center-of-mass energy. Results are presented separately for muon pairs with opposite-sign charges, same-sign charges, and all pairs. A clear peak is observed in all Δ⁢ distributions at Δ⁢∼, consistent with the parent heavy-quark pairs being produced via hard-scattering processes. The widths of that peak, characterized using Cauchy-Lorentz fits to the Δ⁢ distributions, are found to not vary significantly as a function of Pb+Pb collision centrality and are similar for ⁢ and Pb+Pb collisions. This observation will provide important constraints on theoretical descriptions of heavy-quark interactions with the quark-gluon plasma.