Conveners
IS: 1
- Andrea Dainese (INFN - Padova (IT))
IS: 2
- James Lawrence Nagle (University of Colorado Boulder)
IS: 3
- Mateusz Ploskon (Lawrence Berkeley National Lab. (US))
IS: 4
- Peter Alan Steinberg (Brookhaven National Laboratory (US))
IS: 5
- Dinesh Srivastava (National Institute of Advanced Studies, Bengaluru)
IS: 6
- Roberta Arnaldi (Universita e INFN Torino (IT))
IS: 7
- Ralf Averbeck (GSI - Helmholtzzentrum fur Schwerionenforschung GmbH (DE))
IS: 8
- Christian Bierlich (Lund University (SE))
IS: 9
- Helen Caines (Yale University (US))
Quarkonia are considered a distinguished tool to study the strongly-interacting medium formed in ultrarelativistic heavy-ion collisions and they are sensitive to the dense gluonic system at low-x in the initial state of heavy-ion collisions. This can be investigated in photonuclear or proton-nuclear collisions. Furthermore a modification of the quarkonium vector states polarization in...
In high-energy heavy-ion collisions the standard procedure to turn the measured hard-process yields into centrality dependent cross sections is to use normalization factors calculated with the Monte-Carlo Glauber model. Canonically it is assumed that a necessary input, the inelastic nucleon-nucleon cross section, is unmodified wrt. the measured cross section in proton-proton collisions. At the...
Measurements of open heavy-flavor hadron and quarkonium
in heavy-ion collisions provide a powerful tool
to study both initial-state effects on heavy-quark production and final-state interactions
between heavy quarks and the quark-gluon plasma (QGP).
Recent ATLAS measurements of azimuthal anisotropy of muons from heavy-flavor decays in pp and Pb+Pb collisions are presented.
Muons with...
Initial state geometry is a key quantitative component of theoretical descriptions of relativistic heavy-ion collisions. Phenomenological models of the initial state are typically designed to reproduce one-body observables, e.g. charged hadron multiplicity and coefficients of the spatial Fourier decomposition, ๐ฃ๐. However, these models may not simultaneously describe many-body observables such...
Heavy quarks are produced by hard scattering in relativistic heavy-ion collisions. Since heavy quarks are created early in time, those could be used as effective probes for the lead ions and the QGP. In this parallel talk, new results on beauty and charm meson spectra based on the CMS data collected in Run 2 are presented. Those spectra depend on the nuclear parton distribution functions of...
Recently, in the context of the effective kinetic theory developed by Arnold, Moore and Yaffe [1], Berges and Mazeliauskas [2] have shown that the quark-gluon plasma after a sufficiently energetic heavy-ion collision exhibits prescaling, i.e., that the distribution function can be characterized by a scaling distribution plus three dynamical exponents that converge to the universal scaling...
Early time dynamics of heavy-ion collisions represents an important quest to connect the initial conditions with the hydrodynamic evolution and to understand thermalisation in general. Directly sensitive measurements have remained elusive so far. Electromagnetic radiation is a sensitive probe to study QCD systems throughout the full time evolution including the very early stages. In this...
Heavy quarks (charm and beauty) are produced in abundance during the early stage of ultrarelativistic heavy-ion collisions. They therefore experience the full evolution of the quark-gluon plasma (QGP). This makes them unique probes of the initial conditions and of the collective behaviour of the medium as it expands and cools.
The elliptic flow ($v_2$) is an observable that reflects the...
In this talk, we report on phenomenological studies using the recently developed 3-D IP-Glasma initial state. Our 3-D formulation generalizes the boost invariant formulation by including both the rapidity evolution (JIMWLK) and the temporal evolution (Classical Yang-Mills) in the longitudinal direction. Special attention is paid to the local realization of Gauss law in a 3D+1 environment....
We present new results on photon production in heavy ion collisions, including prompt, pre-equilibrium, and thermal photon production from quark gluon plasma and hadron gas phases. We use a model consisting of IP-Glasma initial condition, KoMPoST pre-equilibrium evolution, MUSIC hydrodynamics, and UrQMD transport to both describe hadron production and provide input for the calculation of...
For various centrality selections, we will present $v_{2}$ and $v_{3}$ measurements as a function of particle species and transverse momentum for several beam energies and system size. The longitudinal flow decorrelation $r_n(\eta,\eta_{ref} )$ $(n=2, 3)$ will be also presented at three different collision energies.
Investigating the beam-energy and collision-system size dependence of the...
Fluctuations of event-wise average transverse momentum ($[p_\mathrm{T}]$) and the harmonic flow ($v_n$) carry important information about initial-state geometry. Collisions of nuclei with large quadrupole deformation are predicted to produce an initial state with enhanced shape and size fluctuations, and result in a non-trivial correlation between $v_n$ and $[p_\mathrm{T}]$ in the final state....
We extract the heavy-quark diffusion coefficient $\kappa$ and the resulting momentum broadening $\langle p^2 \rangle$ in an overoccupied gluon plasma. We find several features in the time dependence of the momentum broadening: a short initial rapid growth of $\langle p^2 \rangle$ followed by linear growth in time due to Langevin-type dynamics and damped oscillations around this growth at the...
Recent work by [Kajantie, McLerran, and Paatelainen][1] studies, in a completely classical setting, the gluon bremsstrahlung produced when a sheet of colored glass interacts with a color-charged point particle. Remarkably, the radiation spectrum thus calculated is in qualitative agreement with experiment. I will present here the results of our [paper][2], where we extend these results to...
Relativistic heavy-ion beams are accompanied by a large flux of equivalent photons, giving rise to a set of photon-induced processes. These can lead to photon-photon interactions in both ultraperipheral collisions, where the nuclei do not overlap, as well as in hadronic processes accompanied by the production of hot, dense matter. The latter provides a potentially sensitive electromagnetic...
We investigate the measurement of Hanbury Brown-Twiss (HBT) photon correlations [1] as an experimental tool to discriminate different sources of photon production. To showcase that HBT correlations can distinguish between such sources, we consider two different scenarios in which we enhance the yields from standard hydrodynamical simulations. In the first, additional photons are produced from...
The pre-hydrodynamic evolution of a heavy-ion collision can have important effects on final state observables, and has received significant renewed interest. Here, we utilize a state-of-the-art simulation chain of heavy ion collisions to extend our previous investigation on the effects of pre-hydrodynamic evolution on final-state observables to small systems. Our simulations include different...
Dileptons and photons are unique tools to study the space-time evolution of the hot and dense matter created in ultrarelativistic heavy-ion collisions. They are produced continuously by a variety of sources, in particular prompt and thermal photons and semi-leptonic heavy-flavour hadron decays, during the entire history of the collision and traverse the medium with negligible ๏ฌnal state...
The CMS Collaboration reports on new differential measurements of $\gamma\gamma \rightarrow \mu^{+}\mu^{-}$ production in ultra-peripheral PbPb collisions at $\sqrt{s_{\rm NN}}$ = 5.02~TeV, using data collected during the 2018 LHC run with an integrated luminosity of 1.5~nb$^{-1}$. Photon-photon interactions have been observed in hadronic heavy-ion collisions by STAR and ALTAS experiments at...
At Relativistic Heavy Ion Collider (RHIC) Beam Energy Scan (BES) energies, the dynamics of the pre-hydrodynamic stage and the effects from a nonzero net baryon current become essential components of the dynamical evolution of the collision fireball. We develop a (3+1)-dimensional initial stage model for both energy-momentum and the net baryon current, as dynamical initial conditions for a...
In ultrarelativistic heavy-ion collisions a quark-gluon plasma is created. Its pre-equilibrium evolution includes some fascinating phenomena of QCD. Focusing on the regime when gluonic occupation numbers are large, which can be achieved in the high energy and weak coupling limit, classical-statistical lattice simulations can be used to extract nonperturbative information on the dynamics. In...
Direct photons are emitted unscathed from all the stages of the relativistic heavy ion collisions and therefore are an excellent probe to study the properties of Quark Gluon Plasma (QGP) as they do not interact strongly with the medium. PHENIX has already measured a direct photon excess in Au+Au collisions at 200 GeV in the low momentum region with respect to p+p collisions. With the results...
We propose a new parameterization of the three-dimensional initial condition for the application of the hydrodynamic model to relativistic heavy-ion collisions. In particular, we implement different average-energy production scaling behaviors for different rapidity regions in this proposed ansatz. Near mid-rapidity, the energy deposition is given by the well-tested TRENTo model, with and...
In the initial stages of heavy-ion collisions, topological QCD vacuum fluctuations can induce local parity and charge-parity violations, evincing charge separation in the presence of strong magnetic field, a phenomenon known as the chiral magnetic effect (CME). The CME-driven charge separation is along the magnetic field direction, mainly produced by the spectator protons in relativistic...
Initial conditions for relativistic heavy-ion collisions may be far-from-equilibrium but it is expected that on very short time scales the dynamics converge to a universal attractor that defines hydrodynamic behavior. We investigate how far-from-equilibrium effects may influence experimentally driven searches for the Quantum Chromodynamic critical point at RHIC. We find that the path to the...
Nuclear deformation is a ubiqutous phenomenon for most atomic nuclei, reflecting collective motion induced by interaction between valance nucleons and shell structure. In most cases, the deformation has a quadrupole shape $\beta$ that is axially and refection symmetric, either prolate $\beta>0$ or oblate $\beta<0$. Collisions of deformed nucleus lead to large shape and size fluctuations in the...
Measurements of $W^{\pm}$, $Z$, and charged-hadron production in Pb+Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV
are presented using data recorded by the ATLAS experiment at the LHC in 2015 corresponding to a total integrated luminosity of 0.49\,nb${}^{-1}$.
The the electro-weak (EW) bosons are reconstructed in both the electron and muon decay channels.
The EW boson yields measured in Pb+Pb...
The measured charge distribution of a nucleus is often used to sample
positions of nucleons within the nucleus. However, since nucleons
have finite size, the resulting charge distribution is different from
the sampled distribution. We show that this can have significant
observable effects: Not only does it increase the size of the
nucleus, but also changes the surface diffusiveness. ...
Studies of the phase diagram of the strongly interacting matter is one of the hottest topics in high energy physics. While the transition from hadronic matter to Quark-Gluon Plasma (onset of deconfinement) is now rather uncontroversial, the difficulties in obtaining a unique and quantitative prediction of the QGP signal within the QCD theoretical framework remain and the scientific community...
