Extracting the speed of sound in quark-gluon plasma with ultrarelativistic lead-lead collisions at the LHC

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 determine the sp...

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Bibliographic Details
Authors: Hayrapetyan, A., Bhowmik, Sandeep, Blanco Fernández, Sergio, Brochero Cifuentes, Javier Andrés|||0000-0003-2093-7856, Cabrillo Bartolomé, José Ibán, Calderón Tazón, Alicia|||0000-0002-7205-2040, Duarte Campderros, Jorge|||0000-0003-0687-5214, Fernández García, Marcos|||0000-0002-4824-1087, Gómez Gramuglio, Gervasio|||0000-0002-1077-6553, Lasaosa García, Clara, Martínez Rivero, Celso, Martínez Ruiz del Árbol, Pablo|||0000-0002-7737-5121, Matorras Weinig, Francisco|||0000-0003-4295-5668, Matorras Cuevas, Pablo|||0000-0001-7481-7273, Navarrete Ramos, Efrén|||0000-0002-5180-4020, Piedra Gómez, Jonatan|||0000-0002-9157-1700, Scodellaro, Luca|||0000-0002-4974-8330, Vila Álvarez, Iván|||0000-0002-6797-7209, Vizán García, Jesús Manuel|||0000-0002-6823-8854
Format: article
Publication Date:2024
Country:España
Institution:Universidad de Cantabria (UC)
Repository:UCrea Repositorio Abierto de la Universidad de Cantabria
Language:English
OAI Identifier:oai:repositorio.unican.es:10902/34238
Online Access:https://hdl.handle.net/10902/34238
Access Level:Open access
Keyword:CMS
Quark–gluon plasma
Speed of sound
Ultra-central
QCD equation of state
Description
Summary: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 determine the speed of sound in an extended volume of quark–gluon plasma 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.

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