After briefly reviewing recent developments in the field, we show how far-from-equilibrium hydrodynamics may be systematically defined, for arbitrary flow profiles, in terms of a generalized tensorial expansion with transport coefficients that contain an all order resummation in gradients. We discuss how this approach naturally relates to hydrodynamic attractor solutions found both at weak...
Electroweak bosons are created in the hard scattering processes at the initial stage of heavy-ion collisions and they are insensitive to the presence of the strongly-interacting medium. This makes them clean probes of the initial-state effects in heavy-ion collisions, such as the nuclear modification of the Parton Distribution Functions (nPDFs). Furthermore, their measurement in heavy-ion...
Electroweak bosons provide a unique opportunity to extract the information about the beginning of the temporal evolution of the heavy-ion collision system and understand how the cold nuclear matter effects influence the observables that are measured in heavy-ion collisions.
We investigate the impact of hydrodynamic fluctuations on correlation functions of a relativistic fluid with a conserved U(1) charge. The kinetic equations for the two-point functions of pressure, momentum and heat energy densities are derived within the framework of stochastic hydrodynamics. The leading non-analytic contributions to the energy-momentum tensor as well as the U(1) current are...
We map the infrared dynamics of a relativistic single component (N=1) interacting scalar field theory to that of nonrelativistic complex scalar fields. The Gross-Pitaevskii (GP) equation, describing the real time dynamics of single component ultracold Bose gases, is obtained at first nontrivial order in an expansion proportional to the powers of λϕ^2/m^2 where λ, ϕ and m are the coupling...
Quarkonia, bound states of either a charm and anti-charm quark pair (e.g.
In holographic heavy ion collisions it is possible to follow both the energy density and a globally conserved (baryon) number density throughout the evolution, dual to a metric and Maxwell field in the dual bulk theory, respectively. At infinite coupling, past work has shown that after the collision the baryon number ends up around mid-rapidity, which is different from high energy heavy ion...
In this work, we implement an effective kinetic theory based scattering kernel in the anisotropic hydrodynamics (aHydro) formalism. We compare the realistic kernel results to those obtained from aHydro with the Anderson-Witting scattering kernel (RTA). For the purpose of this study, we consider a conformal system undergoing transversally-homogenous and boost-invariant Bjorken expansion. The...
In this talk we present the measurement of the muon pair continuum in p+p and p+Au collisions at a center of mass energy of 200 GeV. Our novel analysis technique enables the isolation of correlated pairs from semi-leptonic decays of charm and bottom hadrons and from the Drell-Yan process. The measured azimuthal correlations of muon pairs from heavy flavor decays are used to constrain the...
A key ingredient to model heavy ion collisions dynamically is the initial spatial distribution of protons and neutrons inside the nucleus. Traditionally in most theoretical calculations there is no difference between them and their positions are sampled with the Woods-Saxon distribution. However, this assumption has been invalidated by experimental measurements [1]: The diffusiveness of the...
Non-equilibrium Green's functions provide an efficient tool to describe the evolution of the energy-momentum tensor during the early time pre-equilibrium stage, and provide a meaningful to address the question when and to what extent a hydrodynamic description of the system becomes applicable. We present a calculation of the Green's functions describing the evolution of energy density...
The elliptic and triangular flow coefficients,
Relativistic viscous hydrodynamics has been an essential tool in studying the evolution of the Quark Gluon Plasma (QGP) produced in heavy-ion collisions as well as in searching for the critical point expected to be present for more baryon dense systems. With the coming runs of the Beam Energy Scan II at the Relativistic Heavy Ion Collider (RHIC), it will be necessary to implement conserved...
Various microscopic models suggest that local rest frame momentum anisotropies can be large during the early stages of evolution of the quark-gluon plasma (QGP). In recent years, the framework of relativistic anisotropic hydrodynamics (aHydro) has been developed in order to incorporate momentum anisotropic distributions of the QGP constituents into the phenomenological studies of...
We study the heavy-quark momentum diffusion coefficient in gluon plasmas in a self-similar regime using real-time lattice techniques. We observe that the time-evolution of the momentum diffusion coefficient is consistent with a t^(-5/7) power law, as predicted by HTL perturbation theory and self-similarity. Using HTL with our recently acquired data on the spectral function of over-occupied...
Anisotropic flow is well understood as a hydrodynamic response to spatial anisotropies in the system density at early times. This response function can be written explicitly as a systematic expansion in terms of length scales, such that the leading contribution is the familiar eccentricity
We investigate the importance of different features of the initial geometry to anisotropic flow fluctuations in heavy-ion collisions. To that end, we explore the hydrodynamic response of differential flow harmonics
One of the primary goals of flow studies in heavy-ion collisions during recent years is a better understanding of the transport properties of the quark-gluon plasma (QGP), such as the temperature dependence of the shear viscosity to entropy ratio,
In proton-nucleus collisions, the top quark is a novel and theoretically precise probe of the nuclear gluon density at high virtualities
The sPHENIX detector at RHIC, together with the accelerator's unique
capabilities, will enable a spectrum of new or improved measurements
enhancing our understanding of the initial state for nuclear
collisions. Specifically, sPHENIX measurements in spin polarized
proton-proton and proton-nucleus collisions will reveal more about how
partons behave in a nuclear environment, explore spin-spin...
In relativistic kinetic theory, the one-particle distribution function is approximated by an asymptotic perturbative power series in Knudsen number which is divergent. For the Bjorken flow, we expand the distribution function in terms of its moments and study their nonlinear evolution equations. The resulting coupled dynamical system can be solved for each moment consistently using a...
Ever since the discovery of the quark-gluon plasma (QGP) the location of the critical point in the QCD phase diagram - the end point of the supposed first-order transition between hadronic matter and the QGP - has been a principal research goal for heavy-ion collision experiments at RHIC. We use the gauge/gravity duality to study a four-dimensional, strongly-coupled gauge theory with a...
Recently collected data by the ATLAS experiment at the LHC offer opportunities to explore dynamic properties of quark-gluon plasma. A new tool to study these properties is the modified Pearson's correlation coefficient,
An ongoing question in the field is if the collectivity originating in small systems arises from:
- Flow scenario: initial conditions coupled to relativistic hydrodynamics leading to independent particle emissions from the fluid hyper-surface.
or
- Non-flow scenario: genuine 2,4 etc particle correlations from, e.g. a saturation framework.
We note that, in general, the experimentally...
Two particle correlations have been used extensively to study hydrodynamic flow patterns in heavy-ion collisions. In small collision systems, such as p+p and p+A, where particle multiplicities are much smaller than in A+A collisions, non-flow effects from jet correlations, momentum conservation, particle decays, etc. can be significant, even when imposing a large pseudorapidity gap between the...
Centrality fluctuations is one of the main uncertainties for interpreting the centrality dependence of many experimental observables. The centrality fluctuation is constrained by selection based on particle multiplicity in a reference subevent, and contributes to observables measured in another subevent. Due to the asymmetry between forward- and backward-going participating nucleons, the...
We present the first computation of the NLO photon+dijet impact factor in e+A DIS at small
O(
The proposed high-luminosity high-energy Electron Ion Collider (EIC) will provide one of the cleanest environments to precisely determine the nuclear parton distribution functions (nPDFs) in a wide x-
I discuss conformal properties of TMD operators and present the
result of the conformal rapidity evolution of TMD operators in the Sudakov region
The applicability of hydrodynamical models in the extreme conditions produced in heavy ion collisions has not yet been properly understood theoretically. This happens mostly because the derivation of hydrodynamics from microscopic theory often relies on the assumption that the system is sufficiently close to equilibrium -- something difficult to justify in the rapidly expanding systems created...
The next-to-leading order (NLO) Balitsky-Kovchegov (BK) equation describing the high-energy evolution of the scattering between a dilute projectile and a dense target suffers from instabilities unless it is supplemented by a proper resummation of the radiative corrections enhanced by large transverse logarithms. Earlier studies have shown that if one expresses the evolution in terms of the...
The factorization breaking of collective flow in transverse momentum or in pseudorapidity is equivalent to a small decorrelation of flow in different phasespace regions. ATLAS has measured, besides the usual factorization breaking (including both flow magnitude and angle decorrelation), the flow angle decorrelation in pseudorapidity. The latter accounts for about half of the total...
Measurements of dijet production and photo-nuclear interactions in heavy-ion collisions probe several nuclear mechanisms. In particular, dijet measurements in pPb collisions have been shown to be one of the most important tools for constraining the gluon nuclear parton distribution functions (PDFs) at large Bjorken-x. Dijet production in pp and pPb collisions at a nucleon-nucleon...
In this talk, first results on diffraction measurements in pPb collisions will be presented. This measurement utilizes the larger rapidity acceptance of the CMS detector using forward calorimeters such as the forward hadronic calorimeters HF, CASTOR and ZDC. This measurement provides important information for models related to the initial state in pPb collisions, and can also be used to tune...
The measurements of the flow phenomena in Xe+Xe and Pb+Pb collisions provide an excellent opportunity to study the interplay of viscous effects -- which diminish the azimuthal anisotropies more in Xe+Xe compared to Pb+Pb -- and initial geometry fluctuations which have an opposite effect. With the recently developed techniques, used for suppression of non-flow correlations in small systems,...
We study the longitudinal decorrelations of elliptic, triangular and quadrangular flows in heavy-ion collisions at the LHC and RHIC energies. The event-by-event CLVisc (3+1)-dimensional hydrodynamics model, combined with the fully fluctuating AMPT initial conditions, is utilized to simulate the space-time evolution of the strongly-coupled quark-gluon plasma. Detailed analysis is performed for...
Principal Component Analysis (PCA) is a mathematical tool that can capture the most important information in data. As one of the unsupervised algorithms of machine learning, PCA is good at discovering modes or hidden patterns in huge amount of data. It has seen successful applications of PCA in computer vision, data science and physics. Compared with deep learning algorithms, the advantage of...
We present a first-principles description of the primordial state of relativistic nucleus-nucleus collisions, whose density fluctuations and anisotropy we evaluate in the color glass condensate (CGC) framework of high-energy QCD. Relating the primordial anisotropy of the system in our approach to the measured final-state anisotropic flow through a simple linear mapping, we achieve an excellent...
The IP-Jazma model was constructed to elucidate which features of calculations in
the color glass condensate framework are attributable to simple geometry and scaling, and which are manifestations of more complex physics. In this talk we detail comparisons with CGC calculations in the dilute-dense limit, in the dense-dense limit (via IP-Glasma), and more phenomenological models such as...
Jets and photons have been studied to constrain the initial and final stages of collisions between two large nuclei at the Large Hadron Collider.
Measurements of photon and jet production
ATLAS measurements of azimuthal anisotropy and suppression of muons from heavy flavor decays in Pb+Pb collisions are presented. The measurements are extended to smaller systems of
We propose an approach to extract the spatial anisotropy of QGP formed in ultrarelativistic heavy-ion collisions from measured high-pt observables
This talk presents ATLAS measurements of azimuthal anisotropies in
Measurements of anisotropic flow in heavy-ion collisions are an important tool to investigate the nature of the created collectively expanding medium called the Quark-Gluon Plasma (QGP). Recently, striking similarities have been observed in numerous measurements in high multiplicity proton-proton and proton-lead collisions, where no such medium was expected.
In this...
The ALICE Collaboration studied extensively heavy-flavour production at mid- and forward rapidities in small systems at the LHC. The data provide precise tests for pQCD calculations based on the factorization approach and set constraints to Cold Nuclear-Matter effects that can modify heavy-flavour production in p-Pb collisions with respect to pp collisions. At...
To what extent are fluid-dynamic or particle-like excitations at the origin of the flow phenomena observed in pp, pA and AA collisions? And how does the interplay between these two sources of collectivity change as a function of system size and energy density? Here, we address this question in a simple transport theory that interpolates between free-streaming and viscous fluid dynamics. We...
The second- and third-order azimuthal anisotropy Fourier harmonics are studied in pPb collisions at
Our understanding of QCD under extreme conditions has advanced
tremendously following the discovery of the Quark Gluon Plasma and its
detailed characterisation in heavy ion collisions at RHIC and the LHC.
The sPHENIX experiment at RHIC will provide precision measurements of
jet, upsilon and open heavy flavor probes, complementing analogous
measurements at the LHC. The physics program enabled...
In order to investigate the origin of collectivity in small systems, the PHENIX experiment has collected data of p+Au, d+Au and
The STAR Collaboration plans to design, construct, and install a suite of new detectors in the forward rapidity region (2.5 <
Measurements of ``small,'' p+A or d+A, systems at the LHC and RHIC have suggested possible collective flow and, for high event activity collisions, jet modification that may scale with Bjorken x. They also provide input to related questions of the initial state of the proton prior to and throughout its collision with the opposing heavy ion nucleus. This talk presents preliminary measurements...
Among the main LHC experiments, LHCb is the only detector that can run both in collider and fixed-target mode. Internal gas targets of helium, neon and argon have been used so far to collect samples corresponding to integrated luminosities up to 0.1 pb-1. An upgraded target, allowing for a wider choice of target gas species and increasing the gas density by up to two orders of magnitude, is...
Initial state geometry has proved to be decisively important for quantitative descriptions of collective behavior in large collision systems, such as PbPb and AuAu. One of the most remarkable lessons from LHC has been the discovery of collective behavior in small collision systems, but here the notion of spatial structure is not as obvious as in nuclear collisions. In Monte Carlo event...
We present a quantitative assessment of the impact a future Electron-Ion Collider would
have in the determination of parton distribution functions in the proton and parton-to-hadron
fragmentation functions through semi-inclusive deep-inelastic electron-proton scattering data.
Specifically, we estimate the kinematic regions for which the forthcoming data are
expected to have the most...
The 2015 U.S. Nuclear Physics Long-Range Plan recommended the realization of an electron-ion collider (EIC) as the next large construction project in the United States. A U.S.-based EIC has also recently been endorsed by the U.S. National Academy of Sciences.
With the design of an EIC, advancements in theory and further development of phenomenological tools, we are now preparing for the next...
Hosted by the Center for Frontiers in Nuclear Science at Miss Mamie's Spoonbread Too, 366 W 110th St, New York, NY 10025 (10 minute walk from Columbia)
Recently collected data by the ATLAS experiment at the LHC offer opportunities to explore dynamic properties of quark-gluon plasma. A new tool to study these properties is the modified Pearson's correlation coefficient,
We investigate the importance of different features of the initial geometry to anisotropic flow fluctuations in heavy-ion collisions. To that end, we explore the hydrodynamic response of differential flow harmonics vn(pT) to generalized eccentricities ϵn,m of the initial density profile within a realistic hydrodynamic model. Special attention is paid to two-particle angular correlations,...
Hydro simulations are compared with recent experimental data by CMS, on a Principle Component Analysis. The trends for the scaled leading and sub-leading components for n=2,3 agree with data. In contrast, for n=0 there is a qualitative disagreement: the leading component increases with
I discuss conformal properties of TMD operators and present the result of the conformal rapidity evolution of TMD operators in the Sudakov region.
Recent measurements of the
Heavy quarks, owing to their large masses, are predominantly created in the initial hard scatterings in heavy-ion collisions. Therefore, they can play a crucial role in probing the initial-time dynamics in these collisions. Hydrodynamic model calculations suggest that the rapidity-odd directed flow (
