Speaker
Description
Due to large pressure gradients at early times, standard hydrodynamic model simulations of relativistic heavy-ion collisions do not become reliable until $O(1)$ fm/$c$ after the collision. To address this one often introduces a pre-hydrodynamic stage that models the early evolution microscopically, typically as a conformal, weakly interacting gas. In such an approach the transition from the pre-hydrodynamic to the hydrodynamic stage is discontinuous, introducing considerable theoretical model ambiguity. Alternatively, fluids with large anisotropic pressure gradients can be handled macroscopically using the recently developed Viscous Anisotropic Hydrodynamics (VAH). In high-energy heavy-ion collisions VAH is applicable already at very early times, and at later times transitions smoothly into conventional second-order viscous hydrodynamics (VH). We present a Bayesian calibration of a multi-stage dynamical evolution model built around a VAH fluid dynamic core with experimental data for $p_T$-integrated observables from Pb-Pb collisions at the LHC at $\sqrt{s_\mathrm{NN}}=2.76$ TeV. We find that the VAH model has the unique capability of constraining the specific viscosities of the QGP at higher temperatures than other previously used models [1]. We also find that the model has fewer tensions with the $p_T$-integrated input data than the previously calibrated JETSCAPE SIMS model [2]. Finally, we use the calibrated VAH and JETSCAPE SIMS models, with the four different particlization models studied in [2], to predict a number of $p_T$- differential observables, including $p_T$-spectra and anisotropic flow coefficients $v_{2,3,4}\{2\}(p_T)$ for several identified hadron hadron species. We find [3] that the $p_T$-dependence of the anisotropic flow coefficients is very sensitive to the choice of particlization model, and that the VAH predictions agree with available data much better than all available calibrated variants of the JETSCAPE SIMS model. We therefore propose the VAH approach as a superior framework for describing the dynamical evolution of heavy-ion collisions at LHC energies.
*Supported by the NSF CSSI program under grant OAC-2004601 (BAND Collaboration) and by the DOE Office of Science, Office for
Nuclear Physics under Award No. DE-SC0004286.
[1] D. Liyanage et al., arXiv:2302.14184 [nucl-th]
[2] D. Everett et al., PRL 126, 242301 (2021); and PRC 103, 054904 (2021).
[3] C. Gantenberg, research honors thesis, The Ohio State University, April 2023
| Category | Theory |
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