Measurement of the nuclear modification factor of b-jets in 5.02 TeV Pb+Pb collisions with the ATLAS detector

ATLAS Collaboration, Phil Allport, Adrien Auriol, Panagiotis Bellos, Gareth Bird, Juraj Bracinik, David Charlton, Andrew Chisholm, Harry Cooke, Tobias Fitschen, Patrick Freeman, William George, Laura Gonella, Chris Hawkes, Stephen Hillier, Jacob Kempster, Daniel Lewis, Mihaela Marinescu, Antonio Manuel Mendes Jacques Da Costa, Thomas NeepPaul Newman, Konstantinos Nikolopoulos, Júlia Cardoso Silva, Alexis Stampekis, Jurgen Thomas, Paul Thompson, Gov Virdee, Robert Ward, Alan Watson, Miriam Watson

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This paper presents a measurement of b-jet production in Pb+Pb and pp collisions at √SNN=5.02 TeV with the ATLAS detector at the LHC. The measurement uses 260 pb−1 of pp collisions collected in 2017 and 1.4 nb−1 of Pb+Pb collisions collected in 2018. In both collision systems, jets are reconstructed via the anti-kt algorithm. The b-jets are identified from a sample of jets containing muons from the semileptonic decay of b-quarks using template fits of the muon momentum relative to the jet axis. In pp collisions, b-jets are reconstructed for radius parameters R= 0.2 and R= 0.4, and only R= 0.2 jets are used in Pb+Pb collisions. For comparison, inclusive R= 0.2 jets are also measured using 1.7 nb−1 of Pb+Pb collisions collected in 2018 and the same pp collision data as the b-jet measurement. The nuclear modification factor, RAA, is calculated for both b-jets and inclusive jets with R= 0.2 over the transverse momentum range of 80--290 GeV. The nuclear modification factor for b-jets decreases from peripheral to central collisions. The ratio of the b-jet RAA to inclusive jet RAA is also presented and suggests that the RAA for b-jets is larger than that for inclusive jets in central Pb+Pb collisions. The measurements are compared with theoretical calculations and suggest a role for mass and colour-charge effects in partonic energy loss in heavy-ion collisions.
Original languageEnglish
Article number438
Number of pages32
JournalEuropean Physical Journal C
Issue number5
Publication statusPublished - 25 May 2023


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