Elliptic flow is among basic observables that characterize collective effects at the initial stage of formation of quark–gluon plasma in collisions of ultrarelativistic nuclei. The yields of neutral ...pions are measurable up to high transverse-momentum values; therefore, measurement of the elliptic flow for neutral pions is an efficient means for studying quark–gluon plasma. Measurement of the elliptic flow in asymmetric collision systems makes it possible to study the dependence of the elliptic flow on the initial geometry of the system. Two procedures for measuring the elliptic flow for neutral pions in the
asymmetric collision system at the energy of
GeV are considered.
The paper is dedicated to the issues of accumulation of irradiated reactor graphite and possible options for handling it. There are described the advantages of the electrochemical method of ...decontamination of radioactive waste widely used in the nuclear industry. The use of this method to reduce the potential hazard of irradiated reactor graphite is proposed. The processes occurring during the removal of radioactive contamination from the surface of graphite radioactive waste are described. An experimental setup is presented to assess the possibility of using the method of electrochemical decontamination of irradiated graphite. The results of the determining the electrolyzer current-voltage curve and the dissolution rate of the electrodes made of irradiated graphite are presented. According to the results of experimental studies, data on the decontamination coefficients of irradiated graphite were obtained for various radionuclides (60Co, 137Cs, 154Eu, 152Eu) in HNO3, H2SO4, H2O, H2O2, HNO3 + KMnO4, H2SO4 + KMnO4 under various process modes. The evaluation of temperature fields inside the electrolyzer was carried out. The dependence of the removal efficiency of long-lived 14C radionuclide on the total mass loss of irradiated graphite was obtained.
•The principal possibility of decontamination of irradiated graphite by the electrochemical method is shown.•The decontamination coefficients of irradiated graphite with different electrolysis modes are given.•The dependence of the removal efficiency of 14C on the total mass loss of irradiated graphite was obtained.
Direct photons provide valuable insight into the collective properties of Quark–Gluon Plasma. They are emitted throughout the evolution of a heavy-ion collision and do not interact strongly with the ...medium as they leave it. The PHENIX experiment has detected both a large yield and a large elliptic flow of low-
direct photons in Au
Au collisions at
GeV. Calculation of thermal photon emission fall short in describing the yield and the anisotropy at the same time. An intriguing scaling behavior is observed between the low-
direct photon production and the charge particle multiplicity across all
and
collision systems and different beam energies from 39 to 2760 GeV, indicating similar photon sources for all these systems. To provide more insight into photon production mechanism and more constraints on theoretical models, precise measurement of the direct photon anisotropy is needed. This paper reports the measurements of spectra and the flow coefficients of low-momentum with the high statistics of Au
Au collisions data taken in the year 2014. New results provide a 10-fold increase in statistics for the measurement of direct photon yields and their anisotropy.
The PHENIX experiment at RHIC has measured production of K±, Ks, K* and φmesons in p+p, d+Au, Cu+Cu and Au+Au collisions at √sNN = 62.4 and 200 GeV. While p+p collisions provide a baseline and are ...used for precision tests of pQCD calculations, for heavier colliding systems such as d+Au, Cu+Cu and Au+Au nuclear modification factors are studied at different centralities. These systematic studies enrich current understanding of the strange meson production and its difference from light quark hadrons. The role of radial flow and coalescence in particle production is discussed.
Abstract
With the recent observations of collective behavior of produced particles in small collision systems, measurements of the modification of hadron production in small systems have become ...increasingly relevant. To study the properties of possible quark-gluon plasma and cold nuclear matter effects PHENIX has performed measurements of light flavor hadrons (
π
±
,
π
0
,
K
*0
,
φ
, and
p
¯
) in a broad set of projectile-target combinations including
p
+Al,
p
+Au,
d
+Au and
3
He+Au collisions at
s
NN
= 200 GeV. The obtained invariant transverse momentum spectra and nuclear modification factors are presented and compared to theoretical model predictions where available. The observation of baryon enhancement in the new experimental data and the comparisons with different calculations confirm that quark-gluon plasma could be formed in small collision systems. However, the volume and the lifetime of the medium produced in small collision systems might be insufficient for observation of strangeness enhancement and jet quenching effects.
The effect of multidirectional forging on the evolution of the grain structure and the parameters of secondary-phase particles in the aluminum–magnesium alloy (Russian grade 1565ch) has been ...investigated using scanning and transmission electron microscopy. The multidirectional forging was performed at 200, 350, and 500°C to a total strain of 12. Five multidirectional forging cycles (cumulative strain ∑
e
= 12) at 350°C lead to fragmentation of particles of crystallization origin, reduce the average particle size of manganese dispersoids by half, and the average grain size by two orders of magnitude from 200 to 1–2 µm. The ultrafine-grained structure forms in 90% of the sample volume.
Abstract
The main goal of PHENIX expirement, located at Relativistic Heavy-ion collider, is the investigation of quark-gluon plasma (QGP). One of the aspects of the QGP study is describing the ...process of its hadronization. Very important contribution to understanding of hadronization process was given by discovering of anomaly large ratio of protons production to pions production (ρ/π) in Au+Au collisions in comparison to the same ratio in proton-proton collisions. This effect was called baryon puzzle and was explained in a frame of recombination model of hadronization.
Although charged hadrons production has been previously studied in elementary proton-proton collisions and symmetric Au+Au collisions, it has never been investigated before in the large asymmetric collisions systems (such as Cu+Au) or the collisions of large deformed nuclei (U+U). The study of such large collisions systems allows to study features of baryon and meson production versus collision geometry and system size.
Abstract
An important goal of current ultra-relativistic heavy ion research is the investigation of the quark-gluon plasma (QGP). Measurements of elliptic flow lend insight on reaction dynamics and ...are important for defining parameters of viscous hydrodynamic, which can describe QGP behavior. In this paper elliptic flow for φ-mesons in Cu+Au collisions at
s
N
N
=
200
GeV
and in U+U collisions at
s
N
N
=
193
GeV
GeV is studied as a function of kinetic properties and centrality. The obtained results are compared to hydrodynamic model predictions. New FVTX detector and combinations of different approaches of flow measurements provide a possibility to measure the elliptic flow for the
φ
-mesons for the first time as a function of centrality at PHENIX. The elliptic flow for
φ
-mesons in Cu+Au and U+U collisions as function of transverse kinetic energy per one quark follows the trend for other hadrons with respect to the number of quarks in hadrons, regardless of centrality. This result along with agreement of obtained data to hydrodynamic model iEBE-VISHNU predictions suggests that QGP can be described with viscous hydrodynamic with specific viscosity η/s = 1/(4π).
Recent Results from the PHENIX Experiment Larionova, D. M.; Berdnikov, A. Ya; Berdnikov, Ya. A. ...
Physics of atomic nuclei,
12/2023, Letnik:
86, Številka:
6
Journal Article
Recenzirano
The paper highlights recent results from the PHENIX experiment. Measurements of identified charged hadron,
-meson production in
and
collisions as well as measurements of identified charged hadron,
,
...,
,
meson production in small collision systems are presented. Latest results on collectivity effects in small systems and nonprompt photon production in
collisions will also be discussed.
Abstract
Ultrarelativistic ion collisions provide the unique possibility to study the quark-gluon plasma, a state of matter formed in the universe at the very first moments after the Big Bang. The ...minimal temperature and baryon density for the quark-gluon plasma formation requires scrutiny, since the signatures of the quark-gluon plasma formation are observed in large systems (such as Au+Au) at
s
N
N
=
200
GeV
, whereas collective effects in
p
+
p
collisions are not revealed. The φ-meson production measurements are considered to be a convenient tool to investigate the collision dynamics, as it is sensitive to the quark-gluon plasma effects. To interpret the nuclear modification effects and to study the process of the possible QGP formation the comparison with different theoretical models predictions is needed. This paper presents the comparison of the obtained experimental results on φ-meson production in small collision systems (
p
+Al,
p
+Au) at
s
N
N
=
200
GeV
to default and string melting versions of the AMPT model and PYTHIA model predictions. The results indicate that the minimal conditions (temperature and baryon density) for a QGP formation may lie in between in
p
+Al and
p
+Au collisions.
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