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.
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.
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.
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).
In 1933, Borsuk stated a conjecture, which has become classical, that the minimum number of parts of smaller diameter into which an arbitrary set of diameter 1 in
can be partitioned is
. In 1993, ...this conjecture was disproved using sets of points with coordinates 0 and 1. Later, the second author obtained stronger counterexamples based on families of points with coordinates
,
, and
. We establish new lower bounds for Borsuk numbers in families of this type.
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
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.
Abstract
The study of deconfinement state of nuclear matter called quark-gluon plasma (QGP) and phase transition of QGP to hadronic gas is the main goal of high energy physics. Some of the important ...signatures of QGP formation in heavy-ion collisions include strangeness enhancement at intermediate values of the transverse momentum (
ρ
T
) and a jet quenching effect at high ρ
T
values. Nuclear modification factors (
R
AB
) for light hadrons are used to quantify these effects. The
K
*0
and φ mesons can serve as a good probes to investigate QGP properties, because these mesons contain (anti)strange quark and its yields can be measured in a wide
ρ
T
range. Comparison of experimental data with theoretical model calculations is important for understanding the evolution of heavy-ion collision. One of the most commonly used event generators to describe experimental results of collider experiments is Pythia8. This paper shows, that Pythia8 predicts
R
AB
values of
K
*0
and φ less than
R
AB
values in experimental data. Consequently, additional (hidden)strange particle production mechanisms are involved.
PDF
