Chapter 14
Particle Production and Collective
Phenomena in Heavy-Ion Collisions at
STAR and ALICE
Lokesh Kumar
Abstract The recent results from STAR and ALICE experiments are presented
on particle production and collective phenomena. The STAR results suggest that
particle production at lower energies exhibit different features compared to that at
higher energies. The lower energy results hint that there may not be Quark-Gluon
Plasma formation at these energies. Small system results from ALICE experiment
exhibit features similar to those associated generally with heavy-ion collisions. The
results presented here constitute the heavy-ion collision energy range from lowest
energy of
√ s N N = 7.7 GeV to the highest energy of 5.02 TeV.
14.1 Introduction
The high energy heavy-ion collisions recreate the conditions suitable for the formation of Quark-Gluon Plasma (QGP), a state believed to have existed just after the
big bang [1–4]. The Solenoidal Tracker at RHIC (STAR) experiment at Brookhaven
National Laboratory (BNL), USA and A Large Ion Collider Experiment (ALICE)
at CERN, Switzerland are the main experiments using the heavy-ion collisions to
study the QGP formation [1, 5].
The schematic diagram of Quantum Chromo Dynamics is shown in Fig. 14.1 [6].
The x-axis represents the baryon chemical potential μ B and y-axis represents the
temperature T . The phase diagram has many structures, and mainly two phases—
QGP and Hadron gas phase. The phase transition from hadron gas to QGP at μ B ∼
0 is a crossover while at large μ B , a first-order phase transition is expected [7, 8].
In between, the point where the first-order phase transition line ends is called the
QCD critical point [9, 10]. The x-axis and y-axis of the QCD phase diagram can be
accessed through experiments by varying the collision energy.
The main goals of high energy heavy-ion collisions are as follows. Understand the
particle production and freeze-out dynamics, study the QGP properties, and explore
the QCD phase diagram to search for the signals of phase boundary, critical point,
L. Kumar (B)
Department of Physics, Panjab University, Chandigarh 160014, India
e-mail: lokesh@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_14
189
Particle Production and Collective
Phenomena in Heavy-Ion Collisions at
STAR and ALICE
Lokesh Kumar
Abstract The recent results from STAR and ALICE experiments are presented
on particle production and collective phenomena. The STAR results suggest that
particle production at lower energies exhibit different features compared to that at
higher energies. The lower energy results hint that there may not be Quark-Gluon
Plasma formation at these energies. Small system results from ALICE experiment
exhibit features similar to those associated generally with heavy-ion collisions. The
results presented here constitute the heavy-ion collision energy range from lowest
energy of
√ s N N = 7.7 GeV to the highest energy of 5.02 TeV.
14.1 Introduction
The high energy heavy-ion collisions recreate the conditions suitable for the formation of Quark-Gluon Plasma (QGP), a state believed to have existed just after the
big bang [1–4]. The Solenoidal Tracker at RHIC (STAR) experiment at Brookhaven
National Laboratory (BNL), USA and A Large Ion Collider Experiment (ALICE)
at CERN, Switzerland are the main experiments using the heavy-ion collisions to
study the QGP formation [1, 5].
The schematic diagram of Quantum Chromo Dynamics is shown in Fig. 14.1 [6].
The x-axis represents the baryon chemical potential μ B and y-axis represents the
temperature T . The phase diagram has many structures, and mainly two phases—
QGP and Hadron gas phase. The phase transition from hadron gas to QGP at μ B ∼
0 is a crossover while at large μ B , a first-order phase transition is expected [7, 8].
In between, the point where the first-order phase transition line ends is called the
QCD critical point [9, 10]. The x-axis and y-axis of the QCD phase diagram can be
accessed through experiments by varying the collision energy.
The main goals of high energy heavy-ion collisions are as follows. Understand the
particle production and freeze-out dynamics, study the QGP properties, and explore
the QCD phase diagram to search for the signals of phase boundary, critical point,
L. Kumar (B)
Department of Physics, Panjab University, Chandigarh 160014, India
e-mail: lokesh@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_14
189