414 research outputs found
Fourier Coefficients of Asynchronous Collective Motions in Heavy-ion Collisions
We present a novel scenario in heavy-ion collisions where different modes of
collective motions evolve asynchronously in the created nuclear medium. Such
physics mechanisms could each dominate at a distinct evolution stage, or
coexist simultaneously without coordinating with each other. If we employ a
separate single-harmonic Fourier expansion to describe how each asynchronous
collective motion affects particle emission, the particle azimuthal
distribution should be the product of all these expansions. Consequently, cross
terms between collectivity modes appear, and their contributions to
experimental observables could be significant. In particular, we argue that the
chiral magnetic effect (CME) and elliptic flow can develop asynchronously, with
their convolution affecting the observable that is sensitive to the
shear-induced CME. We will use the event-by-event anomalous-viscous fluid
dynamics model to illustrate the effects of this scenario. Besides giving new
insights into searches for the CME, we also propose a feasible experimental
test based on conventional flow harmonics
Event Shape Selection Method in Search of the Chiral Magnetic Effect in Heavy-ion Collisions
The search for the chiral magnetic effect (CME) in heavy-ion collisions has
been impeded by the significant background arising from the anisotropic
particle emission pattern, particularly elliptic flow. To alleviate this
background, the event shape selection (ESS) technique categorizes collision
events according to their shapes and projects the CME observables to a class of
events with minimal flow. In this study, we explore two event shape variables
to classify events and two elliptic flow variables to regulate the background.
Each type of variable can be calculated from either single particles or
particle pairs, resulting in four combinations of event shape and elliptic flow
variables. By employing a toy model and the realistic event generator,
event-by-event anomalous-viscous fluid dynamics (EBE-AVFD), we discover that
the elliptic flow of resonances exhibits correlations with both the background
and the potential CME signal, making the resonance flow unsuitable for
background control. Through the EBE-AVFD simulations of Au+Au collisions at
GeV with various input scenarios, we ascertain that the
optimal ESS strategy for background control entails utilizing the
single-particle elliptic flow in conjunction with the event shape variable
based on particle pairs
An Experimental Review on Heavy-Flavor v
For over a decade now, the primary purpose of relativistic heavy-ion collisions at the Relativistic Heavy-Ion Collider (RHIC) and the Large Hadron Collider (LHC) has been to study the properties of QCD matter under extreme conditions—high temperature and high density. The heavy-ion experiments at both RHIC and LHC have recorded a wealth of data in p+p, p+Pb, d+Au, Cu+Cu, Cu+Au, Au+Au, Pb+Pb, and U+U collisions at energies ranging from sNN=7.7 GeV to 7 TeV. Heavy quarks are considered good probe to study the QCD matter created in relativistic collisions due to their very large mass and other unique properties. A precise measurement of various properties of heavy-flavor hadrons provides an insight into the fundamental properties of the hot and dense medium created in these nucleus-nucleus collisions, such as transport coefficient and thermalization and hadronization mechanisms. The main focus of this paper is to present a review on the measurements of azimuthal anisotropy of heavy-flavor hadrons and to outline the scientific opportunities in this sector due to future detector upgrade. We will mainly discuss the elliptic flow of open charmed meson (D-meson), J/ψ, and leptons from heavy-flavor decay at RHIC and LHC energy
Collective Excitation in High-Energy Nuclear Collisions -- In Memory of Professor Lianshou Liu
We celebrate the legacies of our friend and mentor Professor Lianshou Liu who
was one of the pioneers for the phenomenology of multi-particle interactions
and initiated the physics of relativistic heavy-ion collisions in China. In
this article, we discuss some of the recent exciting experimental observations
on the collective phenomena including collectivity, chirality, criticality,
strangeness production, and thermal equilibrium in high-energy nuclear
collisions. Future directions, especially the physics at high baryon density,
will be discussed with a focus on the first-order phase boundary and
hyperon-nucleon interactions.Comment: 20 pages, 10 figure
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