Strongly interacting quark-gluon plasma (sQGP) is a state of nuclear matter at extremely high values of temperature with quarks and gluons as degrees of freedom. Jet-quenching is one of the evidences ...for sQGP formation in relativistic heavy ion collisions (A+A) and is manifested by suppression of particle yields at high transverse momentum relative to yields of the same particles measured at elementary proton-proton collisions at the same collision energy. Systematic experimental research of jet-quenching is provided by the measurement of nuclear modification factors of light mesons (π0, η, K s 0 , ω etc.) in different A+A systems. Asymmetric system of Cu+Au collisions at s NN =200 GeV is characterised by similar energy density but different collision geometry when compared to symmetric systems (Au+Au or Cu+Cu). This paper presents measurements of π0 and η mesons nuclear modification factors in Cu+Au collisions. Results are compared with ones measured in Au+Au and Cu+Cu collisions at the same collision energy.
Results are presented from measuring nuclear modification factors
R
AA
of the π
0
, η,
K
S
, and ω mesons produced in systems of Cu + Au and U + U collisions at cms energies of
= 200 and 192 GeV, ...respectively, in the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC). The
R
AA
values are found not to depend on the type of neutral meson and to vary in the ~0.4–0.6 and ~0.2–0.3 intervals for central Cu + Au and U + U collisions, respectively. The mean
R
AA
values for different collision systems (Au + Au, Cu + Cu, Cu + Au, and U + U) are found to coincide within the measuring errors when estimated at comparable values of collision energy
, and of the number of nucleons participating in a nucleus–nucleus collision,
N
part
.
Two approaches to the analysis of nonstationary random signals are proposed and studied. The first approach is based on the adaptive Morlet wavelet that allows variations in time and frequency ...resolution of signals using an auxiliary control parameter. The second approach is related to the application of double correlation function that represents correlation of continuous wavelet transforms of two signals calculated in time and frequency domains. The advantages of the proposed correlation function in comparison with alternative correlation functions, in particular, analysis of both time and frequency correlations of nonstationary signals are outlined. Applications of the proposed approaches in the analysis of various transient processes in physics are discussed.
Extensive study of heavy ion collisions at RHIC resulted in the discovery of a strongly coupled Quark Gluon Plasma (sQGP). Since then, the RHIC experiments main effort was directed towards detailed ...study of the new state of matter using more differential and precise measurements. One of the signatures of sQGP formation is the jet quenching effect, which is observed as a suppression of high transverse momenta (pT) hadron yields in heavy-ion (A+A) collisions compared to ones measured in elementary proton-proton (p+p) collisions, which is quantified with the nuclear modification factor (RAA). This paper presents results of π0 and η mesons invariant pT-spectra and RAA measured in U+U collisions at S NN =192GeV in different centrality intervals with PHENIX experiment at RHIC. The π0 and η mesons production in U+U collisions is similarly suppressed within uncertainties and shows similar suppression pattern as the one measured in Au+Au collisions at S NN =200GeV in central and semi-central collisions. In peripheral collisions π0 and η mesons are slightly more suppressed in U+U collisions then in Au+Au.
Nuclear modification factor
R
AA
of π
0
mesons produced in
3
HeAu collisions at a cms energy of
= 200 GeV is extracted from data of the PHENIX experiment at the RHIC. The mean
R
AA
value for π
0
... mesons with
p
T
> 8 GeV/
c
is found to be close to 0.8 for central
3
He + Au collisions.
To study properties of quark-gluon plasma(QGP) is one of the main tasks of modern High Energy Physics. One of the signatures of QGP formation is jet quenching, which was observed as a suppression of ...particle yields (compared to the yield of the same particles in proton-proton collisions) at high transverse momentum region in central collisions of ultra-relativistic heavy nuclei. Jet quenching is the effect of the final state of heavy nuclei collision which is usually explained through parton energy loss in hot and dense medium. Experimentally the jet quenching is studied with nuclear modification factor. This paper presents invariant transverse momentum spectra and nuclear modification factors for π 0 mesons in different classes of centrality in U+U collisions at √SNN=192GeV. Spectra and factors are measured in a wide pT range up to 18 GeV/c for different classes of centrality. In central U+U collisions suppression of neutral π-mesons is the same as the suppression of neutral π-mesons in Au+Au collisions at the similar collision energy and similar numbers of participants.
Studies of collisions between ultrarelativistic heavy nuclei at the Relativistic Heavy Ion Collider (RHIC) led to the discovery of a qualitatively new state of matter (strongly coupled quark–gluon ...plasma), in which quarks and gluons are not bound inside hadrons, but move freely within the volume of the created medium. The U + U collision system with an energy of 192 GeV at the RHIC is the heaviest system of colliding nuclei used in colliding beam experiments and allows us to obtain the highest energy density among systems of ultrarelativistic colliding nuclei. The results are presented from measuring factors of the nuclear modification of π
0
- and η-mesons in (U + U) collisions at an energy of 192 GeV.
Studying the properties of strongly interacting quark–gluon plasma (sQGP) is one of the main aims of modern physics. Measuring the invariant yields of neutral pions is one of the best tools for sQGP ...research, since they can be measured in a wide range of transverse momenta with relatively small statistical and systematic errors. Analysis of specific features of meson production in U + U collisions should help to establish additional constraints on the parameters of theoretical models, and to measure the properties of sQGP more accurately. This work presents the invariant differential transverse-momentum spectra and nuclear modification factors of neutral pions produced in U + U collisions of four different classes of centrality at an energy of 192 GeV.
The first traces of the formation of strongly interacting quark–gluon plasma (sQGP) were found in central collisions of heavy nuclei (
A
+
A
) in experiments on the RHIC collider. The quenching of ...hadron jets, which is seen as a reduction in the yield of particles in
A
+
A
collisions relative to their yield in proton–proton collisions, is one observable sign of sQGP formation. Asymmetrical Cu + Au collisions at 200 GeV, which are characterized by a distinct geometry of nucleus overlap that differs from the geometry in symmetrical collision systems (Au + Au or Cu + Cu), are of special interest in systematic studies of the quenching of hadron jets. The results are presented from measuring invariant transverse-momentum spectra and nuclear modification factors of mesons containing strange quarks in Cu + Au collisions at 200 GeV.
Observations of collective effects in (
A + A
) collisions of heavy nuclei confirm the formation of quark–gluon plasma. The systematic study of collective effects of hot nuclear matter associated ...with the quark–gluon medium and their separation from the effects of cold nuclear matter associated with nucleon medium is one of the main aims of modern high-energy physics. Such studies are conducted using different systems of colliding nuclei. The results are presented from measuring the nuclear modification factors of neutral pions in Cu + Au,
p
+ Au,
d
+ Au, and
3
He + Au collisions at 200 GeV.
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