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Understanding the temperature dependence of the specific shear viscosity $(\eta/s)$ is crucial for characterizing the properties of the QCD matter produced in ultrarelativistic heavy-ion collisions. Since, low-$p_\perp$ theory and data are…

High Energy Physics - Phenomenology · Physics 2025-12-30 Bithika Karmakar , Dusan Zigic , Igor Salom , Jussi Auvinen , Pasi Huovinen , Marko Djordjevic , Magdalena Djordjevic

We investigate the temperature dependence of the shear viscosity to entropy density ratio $\eta/s$ using a piecewise linear parametrization. To determine the optimal values of the parameters and the associated uncertainties, we perform a…

We explore to what extent, and how, high-$p_\perp$ data and predictions reflect the shape and anisotropy of the QCD medium formed in ultrarelativistic heavy-ion collisions. To this end, we use our recently developed DREENA-A framework,…

Nuclear Theory · Physics 2022-10-26 Stefan Stojku , Jussi Auvinen , Lidija Zivkovic , Pasi Huovinen , Magdalena Djordjevic

The transport coefficients of strongly interacting matter are currently subject of intense theoretical and phenomenological studies due to their relevance for the characterization of the quark-gluon plasma produced in ultra relativistic…

High Energy Physics - Phenomenology · Physics 2015-05-05 A. Puglisi , S. Plumari , V. Greco

We demonstrate that measurements of rapidity differential anisotropic flow in heavy ion collisions can constrain the temperature dependence of the shear viscosity to entropy density ratio {\eta}/s of QCD matter. Comparing results from…

Nuclear Theory · Physics 2016-06-01 Gabriel Denicol , Akihiko Monnai , Bjoern Schenke

The suppression of high-$p_\perp$ particles is one of the main signatures of parton energy loss during its passing through the QGP medium, and is reasonably reproduced by different theoretical models. However, a decisive test of the…

Nuclear Theory · Physics 2021-02-24 Stefan Stojku , Bojana Ilic , Marko Djordjevic , Magdalena Djordjevic

We consider $O(N)$ $g\varphi^4$ theory with the coupling $g$ being large, and calculate shear viscosity to entropy density ratio ($\eta/s$). The final result for $\eta/s$ has a form remarkably similar to that obtained from string theory…

High Energy Physics - Phenomenology · Physics 2016-05-23 Namit Mahajan

We perform a global analysis of deep-inelastic $e+p$ scattering data from HERA and transverse energy distributions in $p+p$ and $p+\mathrm{Pb}$ collisions, alongside charged hadron multiplicities in $\mathrm{Pb}+\mathrm{Pb}$ collisions at…

This work reports on investigations of the effects on the evolution of viscous hydrodynamics and on the flow coefficients of thermal dileptons, originating from a temperature-dependent specific shear viscosity $\eta/s (T)$ at temperatures…

Nuclear Theory · Physics 2018-07-18 Gojko Vujanovic , Gabriel S. Denicol , Matthew Luzum , Sangyong Jeon , Charles Gale

We study entropy production in the early stage of high-energy heavy-ion collisions due to shear viscosity. We employ the second-order theory of Israel-Stewart with two different stress relaxation times, as appropriate for strong coupling or…

Nuclear Theory · Physics 2008-11-26 A. Dumitru , E. Molnar , Y. Nara

We investigate the effects of finite baryon density and temperature on the bulk properties of matter formed in relativistic heavy ion collisions within second-order dissipative hydrodynamics. The relativistic fluid evolution equations for…

Nuclear Theory · Physics 2020-08-13 Sukanya Mitra , Subrata Pal

The ratio of shear viscosity to entropy density, $\eta/s$, is computed in various holographic geometries that break translation invariance (but are isotropic). The shear viscosity does not have a hydrodynamic interpretation in such…

High Energy Physics - Theory · Physics 2016-04-20 Sean A. Hartnoll , David M. Ramirez , Jorge E. Santos

The effect of a temperature dependent bulk viscosity to entropy density ratio~($\zeta/s$) along with a constant shear viscosity to entropy density ratio~($\eta/s$) on the space time evolution of the fluid produced in high energy heavy ion…

Nuclear Theory · Physics 2012-01-23 Victor Roy , A. K. Chaudhuri

We present, for the first time, simultaneous determination of shear viscosity ($\eta$) and entropy density ($s$) and thus, $\eta/s$ for equilibrated nuclear systems from $A$ $\sim$ 30 to $A$ $\sim$ 208 at different temperatures. At finite…

Equilibration of highly excited baryon-rich matter is studied within the microscopic model calculations in A+A collisions at energies of BES, FAIR and NICA. It is shown that the system evolution from the very beginning of the collision can…

Nuclear Theory · Physics 2021-02-03 E. Zabrodin , L. Bravina , M. Teslyk , O. Vitiuk

We argue that the phenomenologically inferred ratio of shear viscosity to entropy density of the quark-gluon plasma, $\eta/\s < 0.5$ near the deconfinement temperature $T_c$, can be understood from perturbative QCD. To rebut the widespread,…

High Energy Physics - Phenomenology · Physics 2017-04-24 Greg Jackson , Andre Peshier

Nuclear multifragmentation in intermediate energy heavy ion collisions has long been associated with liquid-gas phase transition. We calculate the shear viscosity to entropy density ratio eta/s for an equilibrated system of nucleons and…

Nuclear Theory · Physics 2014-11-20 Subrata Pal

We explore the influence of a temperature-dependent shear viscosity over entropy density ratio $\eta/s$ on the azimuthal anisotropies v_2 and v_4 of hadrons at various rapidities. We find that in Au+Au collisions at full RHIC energy,…

Nuclear Theory · Physics 2014-11-13 Etele Molnar , Hannu Holopainen , Pasi Huovinen , Harri Niemi

We perform a global Bayesian analysis of a modern event-by-event heavy-ion collision model and LHC data at $\sqrt s$ = 2.76 and 5.02 TeV. After calibration, the model simultaneously describes multiplicity, transverse momentum, and flow data…

Nuclear Theory · Physics 2018-03-14 Jonah E. Bernhard , J. Scott Moreland , Steffen A. Bass

In recent years, there has been a significant effort to extract the temperature-dependent shear ($\eta/s$) and bulk ($\zeta/s$) viscosity over entropy ratios of the quark-gluon plasma from a global comparison of heavy-ion data with results…

Nuclear Theory · Physics 2023-02-28 Fernando G. Gardim , Jean-Yves Ollitrault
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