Bayesian estimation of the specific shear and bulk viscosity of the quark-gluon plasma with additional flow harmonic observables

The transport properties of the strongly coupled quark-gluon plasma created in ultrarelativistic heavy-ion collisions are extracted by Bayesian parameter estimate methods with the latest collision beam energy data from the CERN Large Hadron Collider. This Bayesian analysis includes sophisticated flow harmonic observables for the first time. We found that the temperature dependence of specific shear viscosity appears weaker than in the previous studies. The results prefer a lower value of specific bulk viscosity and a higher switching temperature to reproduce additional observables. However, the improved statistical uncertainties both on the experimental data and hydrodynamic calculations with additional observables do not help to reduce the final credibility ranges much, indicating a need for improving the dynamical collision model before the hydrodynamic takes place. In addition, the sensitivities of experimental observables to the parameters in hydrodynamic model calculations are quantified. It is found that the analysis benefits most from the symmetric cumulants and nonlinear flow modes, which mostly reflect nonlinear hydrodynamic responses, in constraining the temperature dependence of the specific shear and bulk viscosities in addition to the previously used flow coefficients.Peer reviewe

New constraints for QCD matter from improved Bayesian parameter estimation in heavy-ion collisions at LHC

The transport properties of quark-gluon plasma created in relativistic heavy-ion collisions are quantified by an improved global Bayesian analysis using the CERN Large Hadron Collider Pb-Pb data at root s(NN) = 2.76 and 5.02 TeV. The results show that the uncertainty of the extracted transport coefficients is significantly reduced by including new sophisticated collective flow observables from two collision energies for the first time. This work reveals the stronger temperature dependence of specific shear viscosity, a lower value of specific bulk viscosity, and a higher hadronization switching temperature than in the previous studies. The sensitivity analysis confirms that the precision measurements of higher-order harmonic flow and their correlations are crucial in extracting accurate values of the transport properties. (C) 2022 The Author(s). Published by Elsevier B.V.Peer reviewe

Measurement of the Low-Energy Antideuteron Inelastic Cross Section

In this Letter, we report the first measurement of the inelastic cross section for antideuteron-nucleus interactions at low particle momenta, covering a range of 0.3 = 17.4 and 31.8 is obtained. The measured inelastic cross section points to a possible excess with respect to the Glauber model parametrization used in GEANT4 in the lowest momentum interval of 0.3Peer reviewe

Measurement of nuclear effects on ψ(2S) production in p-Pb collisions at sNN−−−√ = 8.16 TeV

Inclusive psi(2S) production is measured in p-Pb collisions at the centre-of-mass energy per nucleon-nucleon pair root s(NN) = 8.16 TeV, using the ALICE detector at the CERN LHC. The production of psi(2S) is studied at forward (2.03<y(cms)Peer reviewe

Investigation of the p-Sigma(0) interaction via femtoscopy in pp collisions

This Letter presents the first direct investigation of the p-Sigma(0) interaction, using the femtoscopy technique in high-multiplicity pp collisions at root s = 13 TeV measured by the ALICE detector. The Sigma(0) is reconstructed via the decay channel to Lambda gamma, and the subsequent decay of Lambda to p pi(-). The photon is detected via the conversion in material to e(+)e(-) pairs exploiting the capability of the ALICE detector to measure electrons at low transverse momenta. The measured p-Sigma(0) correlation indicates a shallow strong interaction. The comparison of the data to several theoretical predictions obtained employing the Correlation Analysis Tool using the Schrodinger Equation (CATS) and the Lednicky-Lyuboshits approach shows that the current experimental precision does not yet allow to discriminate between different models, as it is the case for the available scattering and hypernuclei data. Nevertheless, the p-Sigma(0) correlation function is found to be sensitive to the strong interaction, and driven by the interplay of the different spin and isospin channels. This pioneering study demonstrates the feasibility of a femtoscopic measurement in the p-Sigma(0) channel and with the expected larger data samples in LHC Run 3 and Run 4, the p-Sigma(0) interaction will be constrained with high precision. (C) 2020 European Organization for Nuclear Research. Published by Elsevier B.V.Peer reviewe

Probing the Effects of Strong Electromagnetic Fields with Charge-Dependent Directed Flow in Pb-Pb Collisions at the LHC

The first measurement at the LHC of charge-dependent directed flow (v(1)) relative to the spectator plane is presented for Pb-Pb collisions at root s(NN) = 5.02 TeV. Results are reported for charged hadrons and D-0 mesons for the transverse momentum intervals p(T) > 0.2 GeV/c and 3 <p(T) <6 GeV/c in the 5%-40% and 10%-40% centrality classes, respectively. The difference between the positively and negatively charged hadron v(1) has a positive slope as a function of pseudorapidity eta, d Delta v(1)/d eta = [1.68 +/- 0.49(stat) +/- 0.41(syst)] x 10(-4). The same measurement for D-0 and (D) over bar (0) mesons yields a positive value d Delta v(1)/d eta = [4.9 +/- 1.7(stat)] +/- 0.6(syst)] x 10(-1), which is about 3 orders of magnitude larger than the one of the charged hadrons. These measurements can provide new insights into the effects of the strong electromagnetic field and the initial tilt of matter created in noncentral heavy ion collisions on the dynamics of light (u, d, and s) and heavy (c) quarks. The large difference between the observed Delta v(1) of charged hadrons and D-0 mesons may reflect different sensitivity of the charm and light quarks to the early time dynamics of a heavy ion collision. These observations challenge some recent theoretical calculations, which predicted a negative and an order of magnitude smaller value of d Delta v(1)/d eta for both light flavor and charmed hadrons.Peer reviewe

Two-particle differential transverse momentum and number density correlations in p-Pb collisions at 5.02 TeV and Pb-Pb collisions at 2.76 TeV at the CERN Large Hadron Collider

We present measurements of two-particle differential number correlation functions R-2 and transverse momentum correlation functions P-2, obtained from p-Pb collisions at 5.02 TeV and Pb-Pb collisions at 2.76 TeV. The results are obtained by using charged particles in the pseudorapidity range vertical bar eta vertical bar <1.0 and transverse momentum range 0.2 <p(T) <2.0 GeV/c as a function of pair separation in pseudorapidity, vertical bar Delta eta vertical bar, azimuthal angle Delta phi, and for several charged-particle multiplicity classes. Measurements are carried out for like-sign and unlike-sign charged-particle pairs separately and combined to obtain charge-independent and charge-dependent correlation functions. We study the evolution of the width of the near-side peak of these correlation functions with collision centrality. Additionally, we study Fourier decompositions of the correlators in Delta phi as a function of pair separation vertical bar Delta eta vertical bar. Significant differences in the dependence of their harmonic coefficients on multiplicity classes are found. These differences can be exploited, in theoretical models, to obtain further insight into charged-particle production and transport in heavy-ion collisions. Moreover, an upper limit of nonflow contributions to flow coefficients nu(n) measured in Pb-Pb collisions based on the relative strength of Fourier coefficients measured in p-Pb interactions is estimated.Peer reviewe

One-dimensional charged kaon femtoscopy in p-Pb collisions at root s(NN)=5.02 TeV

The correlations of identical charged kaons were measured in p-Pb collisions at root s(NN) = 5.02 TeV by the ALICE experiment at the LHC. The femtoscopic invariant radii and correlation strengths were extracted from one-dimensional kaon correlation functions and were compared with those obtained in pp and Pb-Pb collisions at root s = 7 TeV and root s(NN) = 2.76 TeV, respectively. The presented results also complement the identical-pion femtoscopic data published by the ALICE collaboration. The extracted radii increase with increasing charged-particle multiplicity and decrease with increasing pair transverse momentum. At comparable multiplicities, the radii measured in p-Pb collisions are found to be close to those observed in pp collisions. The obtained femtoscopic parameters are reproduced by the EPOS 3 hadronic interaction model and disfavor models with large initial size or strong collective expansion at low multiplicities.Peer reviewe

J/psi production as a function of charged-particle multiplicity in p-Pb collisions at root s(NN)=8.16 TeV

Inclusive J/psi yields and average transverse momenta in p-Pb collisions at a center-of-mass energy per nucleon pairs root s(NN) = 8.16 TeV are measured as a function of the charged-particle pseudorapidity density with ALICE. The J/psi mesons are reconstructed at forward (2.03<y(cms)Peer reviewe

Constraining the Chiral Magnetic Effect with charge-dependent azimuthal correlations in Pb-Pb collisions at root s(NN)=2.76 and 5.02 TeV

Systematic studies of charge-dependent two- and three-particle correlations in Pb-Pb collisions at root s(NN) = 2.76 and 5.02 TeV used to probe the Chiral Magnetic Effect (CME) are presented. These measurements are performed for charged particles in the pseudorapidity (eta) and transverse momentum (p(T)) ranges |eta| and gamma(1, - 3) = . The results are used to estimate the contribution of background effects, associated with local charge conservation coupled to anisotropic flow modulations, to measurements of the CME. A blast-wave parametrisation that incorporates local charge conservation tuned to reproduce the centrality dependent background effects is not able to fully describe the measured gamma(1,1). Finally, the charge and centrality dependence of mixed-harmonics three-particle correlations, of the form gamma(1, 2) = , which are insensitive to the CME signal, verify again that background contributions dominate the measurement of gamma(1,1).Peer reviewe