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Title: | Extracting the speed of sound in quark–gluon plasma with ultrarelativistic lead–lead collisions at the LHC |
Authors: | Hayrapetyan, A Tumasyan, A Coldham, K Cole, JE Khan, A Kyberd, P Reid, ID |
Keywords: | CMS;quark–gluon plasma;speed of sound;ultra-central;QCD equation of state |
Issue Date: | 20-Jun-2024 |
Publisher: | IOP Publishing |
Citation: | Hayrapetyan, A. Tumasyan, A. et al. for the benefit of the CMS Collaboration (2024) 'Extracting the speed of sound in quark–gluon plasma with ultrarelativistic lead–lead collisions at the LHC', Reports on Progress in Physics, 87 (7), 077801, pp. 1 - 20. doi: 10.1088/1361-6633/ad4b9b. |
Abstract: | Ultrarelativistic nuclear collisions create a strongly interacting state of hot and dense quark-gluon matter that exhibits a remarkable collective flow behavior with minimal viscous dissipation. To gain deeper insights into its intrinsic nature and fundamental degrees of freedom, we extracted the speed of sound in this medium created using lead-lead (PbPb) collisions at a center-of-mass energy per nucleon pair of 5.02 TeV. The data were recorded by the CMS experiment at the CERN LHC and correspond to an integrated luminosity of 0.607 nb−1. The measurement is performed by studying the multiplicity dependence of the average transverse momentum of charged particles emitted in head-on PbPb collisions. Our findings reveal that the speed of sound in this matter is nearly half the speed of light, with a squared value of 0.241 ± 0.002 (stat) ± 0.016 (syst) in natural units. The effective medium temperature, estimated using the mean transverse momentum, is 219 ± 8 (syst) MeV. The measured squared speed of sound at this temperature aligns precisely with predictions from lattice quantum chromodynamic (QCD) calculations. This result provides a stringent constraint on the equation of state of the created medium and direct evidence for a deconfined QCD phase being attained in relativistic nuclear collisions. |
Description: | Data availability statement: Release and preservation of data used by the CMS Collaboration as the basis for publications is guided by the CMS policy as stated in CMS data preservation, re-use and open access policy (https://cms-docdb.cern.ch/cgi-bin/PublicDocDB/RetrieveFile?docid=6032%252526filename=CMSDataPolicyV1.2.pdf%252526version=2%25257D). A preprint version of this article is available at arXiv:2401.06896v1 [nucl-ex] (https://arxiv.org/abs/2401.06896v1, under article title, 'Extracting the speed of sound in the strongly interacting matter created in ultrarelativistic lead-lead collisions at the LHC'.. It has not been certified by peer review. Comments: Submitted to Reports on Progress in Physics. All figures and tables can be found at http://cms-results.web.cern.ch/cms-results/public-results/publications/HIN-23-003 (CMS Public Pages). Report number: CMS-HIN-23-003, CERN-EP-2023-292. |
URI: | https://bura.brunel.ac.uk/handle/2438/29269 |
DOI: | https://doi.org/10.1088/1361-6633/ad4b9b |
ISSN: | 0034-4885 |
Other Identifiers: | ORCiD: A. Tumasyan https://orcid.org/0009-0000-0684-6742 ORCiD: Joanne E. Cole https://orcid.org/0000-0001-5638-7599 ORCiD: Akram Khan https://orcid.org/0000-0002-4597-4402 ORCiD: Paul Kyberd https://orcid.org/0000-0002-7353-7090 ORCiD: Ivan D. Reid https://orcid.org/0000-0002-9235-779X CMS-HIN-23-003 CERN-EP-2023-292 arXiv:2401.06896v1 [nucl-ex] 077801 |
Appears in Collections: | Dept of Electronic and Electrical Engineering Research Papers |
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