Collision centrality dependencies of charged pion production in 12C+ 181 Ta collisions at 4.2 A GeV/c

The collision centrality dependencies of the average kinematical characteristics of the negative and positive pions, produced in [Formula: see text] collisions at [Formula: see text], were investigated. The ratio [Formula: see text] proved to be [Formula: see text], [Formula: see text] and [Formula: see text] in the peripheral, semicentral, and central [Formula: see text] collision events, respectively, decreasing noticeably with increasing collision centrality. The suppression (decrease) of the ratio [Formula: see text] was observed in the semicentral and central [Formula: see text] collisions as compared to the ratio [Formula: see text], estimated using the simple model for [Formula: see text] collision system. The ratio [Formula: see text] estimated using the simple model agreed well with the corresponding ratio [Formula: see text], estimated for [Formula: see text] collisions at [Formula: see text] based on the Wounded Nucleon Model (WNM). Comparison of the emission angle as well as momentum distributions of the charged pions in the peripheral and central [Formula: see text] collisions revealed the significant decrease of the fraction of the relatively fast charged pions (with smaller emission angles) and increase of the fraction of the relatively slow charged pions (with larger emission angles) with an increase in collision centrality. The results of the present analysis can be useful for analysis of the centrality dependence of the charged pion production in heavy ion collisions at high energies.

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Average transverse expansion velocities and global freeze-out temperatures in central Cu + Cu, Au + Au, and Pb + Pb collisions at high energies at RHIC and LHC

Modern Physics Letters A ◽

10.1142/s0217732320501151 ◽

2020 ◽

Vol 35 (14) ◽

pp. 2050115 ◽

Cited By ~ 1

Author(s):

Khusniddin K. Olimov ◽

Shakhnoza Z. Kanokova ◽

Kosim Olimov ◽

Kadyr G. Gulamov ◽

Bekhzod S. Yuldashev ◽

...

Keyword(s):

Blast Wave ◽

Heavy Ion Collisions ◽

Wave Model ◽

Heavy Ion ◽

Transverse Flow ◽

Collision System ◽

Transverse Expansion ◽

Ion Collisions ◽

Charged Pions ◽

Freeze Out

The experimental invariant transverse momentum [Formula: see text] spectra of the charged pions and kaons, protons and antiprotons, produced at midrapidity in central (0–10%) Au[Formula: see text]Au collisions at [Formula: see text], central (0–10%) Cu[Formula: see text]Cu collisions at [Formula: see text], central (0–10%) Au[Formula: see text]Au collisions at [Formula: see text], and central (0–5%) Pb[Formula: see text]Pb collisions at [Formula: see text], measured by BRAHMS, STAR and ALICE collaborations, were analyzed using three different transverse expansion (blast-wave) models: Siemens–Rasmussen blast-wave model, Simple transverse flow model, and Simplified (hydro-inspired) blast-wave model of Schnedermann et al. Combined (simultaneous) minimum [Formula: see text] fits of the experimental invariant [Formula: see text] spectra of the charged pions and kaons, protons and antiprotons with the above three model functions were conducted, using the identical selected optimal fitting ranges in [Formula: see text] in each studied collision system, and the values of the average transverse expansion velocity [Formula: see text] and global kinetic freeze-out temperature [Formula: see text] and their dependencies on the collision system [Formula: see text] and [Formula: see text] were extracted. The combined (simultaneous) fits using Hagedorn formula with the (embedded) simple transverse flow describe well the experimental invariant [Formula: see text] spectra of the charged pions, kaons, protons and antiprotons in the whole measured range in region [Formula: see text] in the analyzed central heavy ion collisions at RHIC and LHC, reproducing qualitatively well all the established dependencies of the parameters [Formula: see text] and [Formula: see text] on the collision system [Formula: see text] and [Formula: see text]. The obtained results were compared with those of the previous analyses of high energy heavy ion collisions.

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THE BLACK HOLE ENTROPY BOUND AND THE MAXIMUM TEMPERATURE FOR MESON FORMATION IN THE NUCLEAR FIREBALL

Modern Physics Letters A ◽

10.1142/s0217732391003535 ◽

1991 ◽

Vol 06 (33) ◽

pp. 3039-3045 ◽

Cited By ~ 4

Author(s):

JISHNU DEY ◽

MIRA DEY ◽

MARCELO SCHIFFER ◽

LAURO TOMIO

Keyword(s):

Black Hole ◽

Simple Model ◽

Black Hole Entropy ◽

Heavy Ion ◽

Black Hole Thermodynamics ◽

Maximum Temperature ◽

Ion Collisions ◽

Pion Interferometry ◽

Entropy Bound ◽

Confined System

The entropy bound from black hole thermodynamics can be invoked to set limits for temperatures at which hadrons can survive as a confined system. We find that this implies that the pion can be formed in heavy ion collisions, much later than heavier mesons, for example the ρ-meson, when the fireball is cooler. The temperature found in a simple model agree qualitatively with experiment. We also suggest that this may be the reason why in pion interferometry experiments the space-time volume of the pion source seems large.

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PARTON RECOMBINATION IN CLASSICAL CASCADE

Modern Physics Letters A ◽

10.1142/s0217732390002730 ◽

1990 ◽

Vol 05 (28) ◽

pp. 2377-2383 ◽

Cited By ~ 1

Author(s):

A. V. BATUNIN ◽

O. P. YUSHCHENKO

Keyword(s):

Explicit Form ◽

Heavy Ion Collisions ◽

Charged Particles ◽

Heavy Ion ◽

Considerable Decrease ◽

High Energies ◽

Ion Collisions ◽

Parton Cascade ◽

Energy Formula ◽

The Mean

An equation for parton multiplicity in cascade with the recombination 1 → 2 ⊕ 2 → 1 is derived from a Kolmogorov-Chapman equation and solved. An evolution parameter τ of the cascade depends on the c.m. energy [Formula: see text]; an explicit form of the dependence is obtained from the condition that the mean multiplicity of charged particles in pp, [Formula: see text] collisions be reproduced. A considerable decrease in the mean multiplicity in heavy-ion collisions per pair of the colliding nucleons at high energies is predicted and compared to the parton cascade with no recombination.

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