scholarly journals Calculating the initial energy density in heavy ion collisions by including the finite nuclear thickness

2021 ◽  
Vol 103 (2) ◽  
Author(s):  
Todd Mendenhall ◽  
Zi-Wei Lin
Keyword(s):  
Energy Density ◽  
Heavy Ion Collisions ◽  
Heavy Ion ◽  
Initial Energy ◽  
Ion Collisions ◽  
Initial Energy Density

scholarly journals Lifetime estimations from RHIC Au+Au data

2019 ◽  
Vol 34 (26) ◽  
pp. 1950147 ◽  
Author(s):  
Gábor Kasza ◽  
Tamás Csörgő
Keyword(s):  
Energy Density ◽  
Heavy Ion Collisions ◽  
Heavy Ion ◽  
High Energy ◽  
Initial Energy ◽  
Relativistic Hydrodynamics ◽  
Nonmonotonic Dependence ◽  
Ion Collisions ◽  
Initial Energy Density ◽  
Pseudorapidity Density

We discuss a recently found family of exact and analytic, finite and accelerating, [Formula: see text]-dimensional solutions of perfect fluid relativistic hydrodynamics to describe the pseudorapidity densities and longitudinal HBT-radii and to estimate the lifetime parameter and the initial energy density of the expanding fireball in Au[Formula: see text]+[Formula: see text]Au collisions at RHIC with [Formula: see text] GeV and 200 GeV colliding energies. From these exact solutions of relativistic hydrodynamics, we derive a simple and powerful formula to describe the pseudorapidity density distributions in high-energy proton–proton and heavy-ion collisions, and derive the scaling of the longitudinal HBT radius parameter as a function of the pseudorapidity density. We improve upon several oversimplifications in Bjorken’s famous initial energy density estimate, and apply our results to estimate the initial energy densities of high-energy reactions with data-driven pseudorapidity distributions. When compared to similar estimates at the LHC energies, our results indicate a surprising and nonmonotonic dependence of the initial energy density on the energy of heavy-ion collisions.

Sudden increase in the degrees of freedom in dense QCD matter

2021 ◽  
Author(s):  
Aditya Nath Mishra ◽  
Guy Paić ◽  
C. Pajares ◽  
R. P. Scharenberg ◽  
B. K. Srivastava
Keyword(s):  
Charged Particle ◽  
Energy Density ◽  
Heavy Ion Collisions ◽  
Degrees Of Freedom ◽  
Initial Temperature ◽  
Heavy Ion ◽  
Particle Multiplicity ◽  
Sudden Increase ◽  
Alice Experiment ◽  
Ion Collisions

In this paper, we analyzed charged particle transverse momentum spectra in high multiplicity events in proton–proton and nucleus–nucleus collisions at LHC energies from the ALICE experiment using the color string percolation model (CSPM). The color reduction factor and associated string density parameters are extracted for various multiplicity classes in [Formula: see text] collisions and centrality classes for heavy-ion collisions at various LHC energies to study the effect of collision geometry and collision energy. These parameters are used to extract the thermodynamical quantities temperature and the energy density of the hot nuclear matter. A universal scaling is observed in initial temperature when studied as a function of charged particle multiplicity scaled by transverse overlap area. From the measured initial energy density [Formula: see text] and the initial temperature T, a dimensionless quantity [Formula: see text] is constructed which is used to obtain the degrees of freedom (DOF) of the deconfined phase. A two-step behavior and a sudden increase in DOF of [Formula: see text]47 for the ideal gas, above the hadronization temperature (T [Formula: see text] 210[Formula: see text]MeV), are observed in case of heavy-ion collisions at LHC energies.

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