<p>Through model-to-data comparisons from heavy-ion collisions, it has been shown that the quark gluon plasma has an extremely small shear viscosity at vanishing densities. At large baryon densities, significantly less is known about the nature of the shear viscosity from quantum chromodynamics (QCD). Within heavy-ion collisions, there are three conserved charges: baryon number (B), strangeness (S), and electric charge (Q). Here we calculate the shear viscosity in two limits using perturbative QCD (pQCD) and an excluded-volume hadron resonance gas at finite BSQ densities. We then develop a framework that interpolates between these two limits such that shear viscosity is possible to calculate across a wide range of finite BSQ densities. We find that the pQCD and hadron resonance gas calculations have different BSQ density dependencies such that a rather nontrivial shear viscosity appears at finite densities.</p>

Germany

Isabella Danhoni

United States

Jordi Salinas San Martín

Jacquelyn Noronha-Hostler

Shear viscosity from perturbative quantum chromodynamics to the hadron resonance gas at finite baryon, strangeness, and electric charge densities

We combine, for the first time, event-by-event <math><msub><mrow><mi>T</mi></mrow><mrow><mi>R</mi></mrow></msub><mi>ENTo</mi></math> initial conditions with the relativistic viscous hydrodynamic model v-USPhydro and the Monte Carlo event generator JEWEL to make predictions for the nuclear modification factor <math><msub><mrow><mi>R</mi></mrow><mrow><mi>A</mi><mi>A</mi></mrow></msub></math> and jet azimuthal anisotropies <math><msub><mrow><mi>v</mi></mrow><mrow><mi>n</mi></mrow></msub><mrow><mo>{</mo><mn>2</mn><mo>}</mo></mrow></math> in <math><msqrt><mrow><msub><mrow><mi>s</mi></mrow><mrow><mi>N</mi><mi>N</mi></mrow></msub></mrow></msqrt><mo>=</mo><mn>5.02</mn><mspace width="0.2em"></mspace><mrow><mi>TeV</mi></mrow></math> PbPb collisions for multiple centralities and values of the jet cone radius R. The R-dependence of <math><msub><mrow><mi>R</mi></mrow><mrow><mi>A</mi><mi>A</mi></mrow></msub></math> and <math><msub><mrow><mi>v</mi></mrow><mrow><mn>2</mn></mrow></msub><mrow><mo>{</mo><mn>2</mn><mo>}</mo></mrow></math> strongly depends on the presence of recoiling scattering centers. We find a small jet <math><msub><mrow><mi>v</mi></mrow><mrow><mn>3</mn></mrow></msub><mrow><mo>{</mo><mn>2</mn><mo>}</mo></mrow></math> in mid-central collisions and consistent results in wide jet <math><msub><mrow><mi>p</mi></mrow><mrow><mi>T</mi></mrow></msub></math> regions and centralities with ATLAS data.