Accessing the speed of sound in relativistic ultracentral nucleus-nucleus collisions using the mean transverse momentum

Abstract

It has been argued that the speed of sound of the strong interaction at high temperature can be measured using the variation of the mean transverse momentum with the particle multiplicity in ultracentral heavy-ion collisions. We test this correspondence by running hydrodynamic simulations at zero impact parameter with several equations of state, at several colliding energies from 0.2 TeV to 15 TeV per nucleon pair. The correspondence is found to be precise and robust for a smooth, boost-invariant fluid and an ideal detector. We discuss the differences between this ideal setup and an actual experiment. We conclude that the extraction of the speed of sound from data is reliable, and that the main uncertainty comes from our poor knowledge of the distribution of density fluctuations at the early stages of the collision.

v2: 8 pages, 4 figures. Added new section IV - E. Matches the published version

References in corpus (18)

• Elliptic and triangular flow in event-by-event (3+1)D viscous hydrodynamics
• Alternative ansatz to wounded nucleon and binary collision scaling in high-energy nuclear collisions
• Fully integrated transport approach to heavy ion reactions with an intermediate hydrodynamic stage
• Multi-system Bayesian constraints on the transport coefficients of QCD matter
• Bayesian analysis of heavy ion collisions with the heavy ion computational framework Trajectum
• Relativistic hydrodynamics for heavy-ion collisions
• Event-by-event mean $p_{\mathrm{T}}$ fluctuations in pp and Pb-Pb collisions at the LHC
• Transverse momentum fluctuations and their correlation with elliptic flow in nuclear collision
• Directed flow at mid-rapidity in event-by-event hydrodynamics
• Longitudinal fluctuations of the fireball density in heavy-ion collisions
• From hydro to jet quenching, coalescence and hadron cascade: a coupled approach to solving the $R_{AA}\otimes v_2$ puzzle
• Transport and hydrodynamics in the chiral limit
• Interplay between core and corona components in high-energy nuclear collisions
• Continuous description of fluctuating eccentricities
• Effective shear and bulk viscosities for anisotropic flow
• Fluid velocity from transverse momentum spectra
• Assessing the ultracentral flow puzzle in hydrodynamic modeling of heavy-ion collisions
• Multiplicity fluctuations and correlations in 5.02 TeV p+Pb collisions at zero impact parameter

Cited by in corpus (10)

• Disentangling sources of momentum fluctuations in Xe+Xe and Pb+Pb collisions with the ATLAS detector
• Analytical insights into the interplay of momentum, multiplicity and the speed of sound in heavy-ion collisions
• Impact parameter dependence of anisotropic flow: Bayesian reconstruction in ultracentral nucleus-nucleus collisions
• Study of $⟨p_{\mathrm{T}}⟩$ and its higher moments, and extraction of the speed of sound in Pb-Pb collisions with ALICE
• Feasibility of measuring the speed of sound of the quark-gluon plasma from the multiplicity and mean $p_T$ of ultracentral heavy-ion collisions
• The size of the quark-gluon plasma in ultracentral collisions: impact of initial density fluctuations on the average transverse momentum
• Extracting the speed of sound of QCD from transverse momentum fluctuations
• High-order fluctuations of temperature in hot QCD matter
• Revisiting the soft-hard separation in the transverse momentum spectra of $pp$ collisions
• Effect of event classification on the Tsallis-thermometer