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

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Abstract

jats:titleAbstract</jats:title>jats:pThis paper presents a measurement of jats:italicb</jats:italic>-jet production in Pb+Pb and jats:italicpp</jats:italic> collisions at jats:inline-formulajats:alternativesjats:tex-math$$\sqrt{s_{\text {NN}}}=5.02$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:mrow mml:msqrt mml:msub mml:mis</mml:mi> mml:msub <mml:mrow /> mml:mtextNN</mml:mtext> </mml:msub> </mml:msub> </mml:msqrt> mml:mo=</mml:mo> mml:mn5.02</mml:mn> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> TeV with the ATLAS detector at the LHC. The measurement uses 260 jats:inline-formulajats:alternativesjats:tex-math$$\text {pb}^{-1}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:msup mml:mtextpb</mml:mtext> mml:mrow mml:mo-</mml:mo> mml:mn1</mml:mn> </mml:mrow> </mml:msup> </mml:math></jats:alternatives></jats:inline-formula> of jats:italicpp</jats:italic> collisions collected in 2017 and 1.4 jats:inline-formulajats:alternativesjats:tex-math$$\text {nb}^{-1}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:msup mml:mtextnb</mml:mtext> mml:mrow mml:mo-</mml:mo> mml:mn1</mml:mn> </mml:mrow> </mml:msup> </mml:math></jats:alternatives></jats:inline-formula> of Pb+Pb collisions collected in 2018. In both collision systems, jets are reconstructed via the anti-jats:inline-formulajats:alternativesjats:tex-math$$k{t}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:msub mml:mik</mml:mi> mml:mit</mml:mi> </mml:msub> </mml:math></jats:alternatives></jats:inline-formula> algorithm. The jats:italicb</jats:italic>-jets are identified from a sample of jets containing muons from the semileptonic decay of jats:italicb</jats:italic>-quarks using template fits of the muon momentum relative to the jet axis. In jats:italicpp</jats:italic> collisions, jats:italicb</jats:italic>-jets are reconstructed for radius parameters jats:inline-formulajats:alternativesjats:tex-math$$R= 0.2$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:mrow mml:miR</mml:mi> mml:mo=</mml:mo> mml:mn0.2</mml:mn> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> and jats:inline-formulajats:alternativesjats:tex-math$$R= 0.4$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:mrow mml:miR</mml:mi> mml:mo=</mml:mo> mml:mn0.4</mml:mn> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula>, and only jats:inline-formulajats:alternativesjats:tex-math$$R= 0.2$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:mrow mml:miR</mml:mi> mml:mo=</mml:mo> mml:mn0.2</mml:mn> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> jets are used in Pb+Pb collisions. For comparison, inclusive jats:inline-formulajats:alternativesjats:tex-math$$R= 0.2$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:mrow mml:miR</mml:mi> mml:mo=</mml:mo> mml:mn0.2</mml:mn> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> jets are also measured using 1.7 jats:inline-formulajats:alternativesjats:tex-math$$\text {nb}^{-1}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:msup mml:mtextnb</mml:mtext> mml:mrow mml:mo-</mml:mo> mml:mn1</mml:mn> </mml:mrow> </mml:msup> </mml:math></jats:alternatives></jats:inline-formula> of Pb+Pb collisions collected in 2018 and the same jats:italicpp</jats:italic> collision data as the jats:italicb</jats:italic>-jet measurement. The nuclear modification factor, jats:inline-formulajats:alternativesjats:tex-math$$R_\text {AA}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:msub mml:miR</mml:mi> mml:mtextAA</mml:mtext> </mml:msub> </mml:math></jats:alternatives></jats:inline-formula>, is calculated for both jats:italicb</jats:italic>-jets and inclusive jets with jats:inline-formulajats:alternativesjats:tex-math$$R= 0.2$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:mrow mml:miR</mml:mi> mml:mo=</mml:mo> mml:mn0.2</mml:mn> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> over the transverse momentum range of 80–290 GeV. The nuclear modification factor for jats:italicb</jats:italic>-jets decreases from peripheral to central collisions. The ratio of the jats:italicb</jats:italic>-jet jats:inline-formulajats:alternativesjats:tex-math$$R_\text {AA}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:msub mml:miR</mml:mi> mml:mtextAA</mml:mtext> </mml:msub> </mml:math></jats:alternatives></jats:inline-formula> to inclusive jet jats:inline-formulajats:alternativesjats:tex-math$$R_\text {AA}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:msub mml:miR</mml:mi> mml:mtextAA</mml:mtext> </mml:msub> </mml:math></jats:alternatives></jats:inline-formula> is also presented and suggests that the jats:inline-formulajats:alternativesjats:tex-math$$R_\text {AA}$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> mml:msub mml:miR</mml:mi> mml:mtextAA</mml:mtext> </mml:msub> </mml:math></jats:alternatives></jats:inline-formula> for jats:italicb</jats:italic>-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.</jats:p>

Description

Acknowledgements: We thank CERN for the very successful operation of the LHC, as well as the support staff from our institutions without whom ATLAS could not be operated efficiently. We acknowledge the support of ANPCyT, Argentina; YerPhI, Armenia; ARC, Australia; BMWFW and FWF, Austria; ANAS, Azerbaijan; CNPq and FAPESP, Brazil; NSERC, NRC and CFI, Canada; CERN; ANID, Chile; CAS, MOST and NSFC, China; Minciencias, Colombia; MEYS CR, Czech Republic; DNRF and DNSRC, Denmark; IN2P3-CNRS and CEA-DRF/IRFU, France; SRNSFG, Georgia; BMBF, HGF and MPG, Germany; GSRI, Greece; RGC and Hong Kong SAR, China; ISF and Benoziyo Center, Israel; INFN, Italy; MEXT and JSPS, Japan; CNRST, Morocco; NWO, Netherlands; RCN, Norway; MEiN, Poland; FCT, Portugal; MNE/IFA, Romania; MESTD, Serbia; MSSR, Slovakia; ARRS and MIZŠ, Slovenia; DSI/NRF, South Africa; MICINN, Spain; SRC and Wallenberg Foundation, Sweden; SERI, SNSF and Cantons of Bern and Geneva, Switzerland; MOST, Taiwan; TENMAK, Türkiye; STFC, United Kingdom; DOE and NSF, United States of America. In addition, individual groups and members have received support from BCKDF, CANARIE, Compute Canada and CRC, Canada; PRIMUS 21/SCI/017 and UNCE SCI/013, Czech Republic; COST, ERC, ERDF, Horizon 2020 and Marie Skłodowska-Curie Actions, European Union; Investissements d’Avenir Labex, Investissements d’Avenir Idex and ANR, France; DFG and AvH Foundation, Germany; Herakleitos, Thales and Aristeia programmes co-financed by EU-ESF and the Greek NSRF, Greece; BSF-NSF and MINERVA, Israel; Norwegian Financial Mechanism 2014–2021, Norway; NCN and NAWA, Poland; La Caixa Banking Foundation, CERCA Programme Generalitat de Catalunya and PROMETEO and GenT Programmes Generalitat Valenciana, Spain; Göran Gustafssons Stiftelse, Sweden; The Royal Society and Leverhulme Trust, United Kingdom. The crucial computing support from all WLCG partners is acknowledged gratefully, in particular from CERN, the ATLAS Tier-1 facilities at TRIUMF (Canada), NDGF (Denmark, Norway, Sweden), CC-IN2P3 (France), KIT/GridKA (Germany), INFN-CNAF (Italy), NL-T1 (Netherlands), PIC (Spain), ASGC (Taiwan), RAL (UK) and BNL (USA), the Tier-2 facilities worldwide and large non-WLCG resource providers. Major contributors of computing resources are listed in Ref. [80].

Keywords

5106 Nuclear and Plasma Physics, 5107 Particle and High Energy Physics, 51 Physical Sciences

Journal Title

European Physical Journal C

Conference Name

Journal ISSN

1434-6044
1434-6052

Volume Title

Publisher

Springer Science and Business Media LLC