Conveners
New Theory: (1)
- Krishna Rajagopal (Massachusetts Inst. of Technology (US))
New Theory: (2)
- Ulrich Heinz
New Theory: (3)
- Peter Levai (Wigner Research Centre for Physics (Wigner RCP) (HU))
We report on progress in understanding thermalization in QCD at the full quantum level. Previous studies of thermalization of highly excited states in QCD, as they arise in heavy ion collisions, have either involved the (semi-)classical evolution of highly occupied gluon states or kinetic theory. Both approaches omit or approximate essential properties of quantum mechanical systems including...
We discuss the evolution of initial momentum anisotropy in the early-stage quark-gluon plasma. We use kinetic theory to study the far-from-equilibrium evolution of an expanding plasma with an anisotropic momentum-space distribution. We identify slow and fast degrees of freedom in the far-from-equilibrium plasma from the evolution of moments of this distribution. At late times, the slow modes...
Viscous hydrodynamics serves as a successful mesoscopic description of the QGP produced in relativistic heavy-ion collisions. In order to investigate, how such an effective description emerges from the underlying microscopic dynamics we calculate the non-hydrodynamic and hydrodynamic modes of linear response in the sound channel from a first-principle calculation in kinetic theory. We do this...
The success of thermal models in extracting freeze-out parameters from particle yields near midrapidity is well known. However, it is essential to investigate their performance with rapidity-dependent measurements at low collision energies, where boost-invariance is expected to be strongly violated. In this study, we calibrate a (3+1)-dimensional multistage hydrodynamic framework using...
Wouldn't it be nice to solve large N QCD analytically? While QCD is hard, it is fairly easy to solve scalar field theories with many components, such as the O(N) model in the large N limit. Traditional wisdom has it that such theories are ill defined because they have the wrong beta function, possess a Landau pole, and are quantum trivial for N=1. In this talk, I throw out conventional wisdom,...
We consider non-equilibrium evolution of non-Gaussian fluctuations crucial for the QCD critical point search in heavy-ion collision experiments. We rely on the hierarchy of relaxation time scales, which emerges in the hydrodynamic regime near the critical point. We focus on the slowest modes which are responsible for observable signatures of the critical point. We derive evolution equations...
The proper treatment of hadronic resonances plays an important role for many aspects of heavy ion collisions. We expect this to be the case also for hadronization, due to the large degeneracies of excited states, and the abundant production of hadrons from their decays. We show how a comprehensive treatment of excited meson states can be incorporated into quark recombination, and in extension,...
The study of thermal fluctuations in relativistic hydrodynamics is essential for understanding physics near the expected critical endpoint in the QCD phase diagram. Furthermore, the incorporation of stochastic fluctuations may be important for the modeling of hydrodynamics in small systems such as proton-proton and proton-nucleus collisions. We present a new general formalism for introducing...
Unpolarized protons can generate transversely polarized quarks or linearly polarized gluons through a distribution known as the Boer-Mulders' function. The fragmentation of similarly polarized partons to unpolarized hadrons is called the Collins' function. Both of these functions include correlations between the spin or polarization and the relative transverse momentum of the incoming parton...
We study cold nuclear matter effects on Drell-Yan production at small and moderate $p_T$ in proton/pion-nucleus collisions using a new transverse-momentum dependent (TMD) factorization framework. Both collisional broadening and medium-induced radiative corrections in the initial state are considered in the soft-collinear effective theory with Glauber gluons (SCET$_{G}$) approach. We...
We study the boost-invariant non-conformal Boltzmann equation in the relaxation-time approximation using special moments of the distribution function and investigate how hydrodynamical behavior emerges as the plasma transits from the far-off-equilibrium free-streaming regime to the hydrodynamic regime. The infinite hierarchy of moments can be truncated by keeping only the three lowest moments...
We propose a method to find local plane wave solutions to linearized equations of motion of relativistic hydrodynamics in inhomogeneous backgrounds, i.e., when fluid is rigidly moving with nonzero thermal vorticity in equilibrium. Our method is based on extending the conserved currents to the tangent bundle, using Wigner transforms. The Wigner-transformed conserved currents can then be Fourier...
Determining the existence and the location of the QCD critical point remains a major goal in the heavy-ion collision experiments. A crucial theoretical input for achieving this goal is mapping the QCD equation of state in the presence of baryon chemical potential (mu) which at the moment is limited to small values of mu, away from the critical point. I present a new framework for...
We investigate whether early and late time attractors for non-conformal kinetic theories exist by computing the time-evolution of a large set of moments of the one-particle distribution function. For this purpose we make use of a previously obtained exact solution of the 0+1D boost-invariant massive Boltzmann equation in relaxation time approximation. We extend prior attractor studies of...
For heavy ion collisions in the TeV beam energy region, the large number of initial hard scatterings create a richly "doped" hot quark-gluon plasma containing many charm quarks/anti-quarks, thus providing a uniquely "charming" environment for the massive production of heavy flavor exotic hadrons such as the $\chi_{c1}$ (also known as X(3872)), X(6900) and Tcc states. While such exotic states...
We explore the far-off-equilibrium aspects of the (1+1)-dimensional early-stage evolution of a weakly-coupled quark-gluon plasma using hydrodynamics and kinetic theory. For a large set of far-off-equilibrium initial conditions we observe that the macroscopic evolution appears to violate simple rules based on the second law of thermodynamics. We provide an in-depth microscopic understanding of...
We have investigated the charge-dependent anisotropic flow in high-energy heavy-ion collisions, using relativistic resistive magneto-hydrodynamics (RRMHD). For the description of time evolution of the ultraintense electromagnetic fields produced just after the collisions, construction of the relativistic resistive magneto-hydrodynamics (RRMHD) is indispensable
We construct a relativistic...
A central question in heavy-ion collisions is how the initial far-from-equilibrium medium evolves and thermalizes. In this work we use the two-particle irreducible (2PI) effective action for the first time to answer this question. This requires including the fast longitudinal expansion that characterizes heavy-ion collisions. Our framework, the 2PI effective action, is non-perturbative and...
A double copy between 2 > N QCD amplitudes and Gravity amplitudes at high energies was first discovered by Lipatov in 1981. In published work with G. Dvali[1], we showed how a double copy between Black Holes and the CGC arises, with both systems saturating the Bekenstein bound. We discuss how this dual picture points to some missing features of the CGC. Most importantly theoretical techniques...
