Chapter 13
Elliptic Flow in Relativistic Heavy-Ion
Collisions
Madan M. Aggarwal
Abstract The basic aim of the heavy-ion physics is to investigate matter at extreme
densities and temperatures where quarks and gluons are no longer confined inside
hadrons. Such a state of matter, that may have existed a few microseconds after the
Big Bang, is created in the laboratory by colliding nuclei at the Relativistic Heavy-Ion
Collider (RHIC), Brookhaven, and at the Large Hadron Collider (LHC), CERN at
top center of mass energies
√
s NN = 200 GeV and 5.02 TeV, respectively. The large
elliptic flow and number of constituent quark (NCQ) scaling observed at the RHIC
and similar observations at the LHC with some deviation indicate the formation of
de-confined state in relativistic heavy-ion collisions. The elliptic flow measurement
and its dependence on collision centrality, transverse momentum, particle species,
etc., will be presented.
13.1 Introduction
The Quantum Chromodynamics (QCD) predicted a phase transition from normal
nuclear matter into the de-confined plasma phase of quarks and gluons at an energy
density of ∼1 GeV/fm
3 or for a critical temperature T c ∼ 170 MeV [1, 2]. The
Ultra-relativistic heavy-ion collisions provide a very good opportunity to create and
observe Quark-Gluon Plasma (QGP) in the laboratory. The QCD phase diagram,
baryon chemical potential (μ B ) versus temperature (T), is shown in Fig. 13.1. A
solid line separates the hadronic region (at comparatively low temperature or chemical potential) from the quark-gluon plasma. One expects the phase transition line
to end at a critical point as indicated in the figure. The RHIC beam energy scan
programme searches for a critical point in the phase diagram [3]. The Present and
future nucleus-nucleus experiments are depicted in the diagram. The LHC and the
RHIC are investigating the baryon free QGP at high temperature (low μ B ) whereas
experiments at the FAIR will look for the baryon rich QGP at low T (high μ B ).
M. M. Aggarwal (B)
Department of Physics, Panjab University, Chandigarh, India
e-mail: aggarwal@pu.ac.in
© Springer Nature Singapore Pte Ltd. 2021
R. K. Puri et al. (eds.), Advances in Nuclear Physics, Springer Proceedings
in Physics 257, https://doi.org/10.1007/978-981-15-9062-7_13
161
Elliptic Flow in Relativistic Heavy-Ion
Collisions
Madan M. Aggarwal
Abstract The basic aim of the heavy-ion physics is to investigate matter at extreme
densities and temperatures where quarks and gluons are no longer confined inside
hadrons. Such a state of matter, that may have existed a few microseconds after the
Big Bang, is created in the laboratory by colliding nuclei at the Relativistic Heavy-Ion
Collider (RHIC), Brookhaven, and at the Large Hadron Collider (LHC), CERN at
top center of mass energies
√
s NN = 200 GeV and 5.02 TeV, respectively. The large
elliptic flow and number of constituent quark (NCQ) scaling observed at the RHIC
and similar observations at the LHC with some deviation indicate the formation of
de-confined state in relativistic heavy-ion collisions. The elliptic flow measurement
and its dependence on collision centrality, transverse momentum, particle species,
etc., will be presented.
13.1 Introduction
The Quantum Chromodynamics (QCD) predicted a phase transition from normal
nuclear matter into the de-confined plasma phase of quarks and gluons at an energy
density of ∼1 GeV/fm
3 or for a critical temperature T c ∼ 170 MeV [1, 2]. The
Ultra-relativistic heavy-ion collisions provide a very good opportunity to create and
observe Quark-Gluon Plasma (QGP) in the laboratory. The QCD phase diagram,
baryon chemical potential (μ B ) versus temperature (T), is shown in Fig. 13.1. A
solid line separates the hadronic region (at comparatively low temperature or chemical potential) from the quark-gluon plasma. One expects the phase transition line
to end at a critical point as indicated in the figure. The RHIC beam energy scan
programme searches for a critical point in the phase diagram [3]. The Present and
future nucleus-nucleus experiments are depicted in the diagram. The LHC and the
RHIC are investigating the baryon free QGP at high temperature (low μ B ) whereas
experiments at the FAIR will look for the baryon rich QGP at low T (high μ B ).
M. M. Aggarwal (B)
Department of Physics, Panjab University, Chandigarh, India
e-mail: aggarwal@pu.ac.in
© Springer Nature Singapore Pte Ltd. 2021
R. K. Puri et al. (eds.), Advances in Nuclear Physics, Springer Proceedings
in Physics 257, https://doi.org/10.1007/978-981-15-9062-7_13
161