The results of a fractal analysis of Monte Carlo AuAu events at the c.m. collision energy of
GeV on the basis of the method of the System of Equations of P-basic Coverage (SePaC) are presented. A ...MultiPhase Transport (AMPT) model is used to generate collision events. The transverse momentum
of negatively charged particles detected in the pseudorapidity range of
in events of different centrality between (0–5)
and (30–40)
is considered as the variable under study. Sets of random events and Monte Carlo fractals are compared. The difference in the behavior of the dependence of the fraction of events reconstructed as fractals on the parameters of the method for different types of data are demonstrated. Optimum values of the parameters for an analysis of AMPT AuAu events are found. It is indicated that the portion of Prtn events reconstructed as fractals depend on the centrality and multiplicity in AuAu and random events, respectively. Insignificant distinctions in the behavior of the distributions with respect to dimension
for different centrality classes are found. Two event classes differing in the shape of transverse-moment spectra are singled out among AMPT AuAu events.
Monte Carlo (MC)
events at an energy of
= 200 GeV, obtained using the AMPT generator, MC fractals, and events with randomly distributed particles are analyzed by the
method. The dependence of the ...portion
of the events under study, defined as fractals, on the method parameter
is investigated. It has been established that the hypotheses of independent and dependent formation of fractals correspond to different regions of behavior of
for AMPT
events. The
method makes it possible to extract AMPT
events with equal fractal dimensions
at different levels. The distribution of events by
are different for used hypotheses. Events identified by the hypothesis of independent devision have a group of leading particles according to
,
and the remaining ones exhibit exponential behavior of the
spectrum. The use of background suppression criteria describing the statistical characteristics of structures at different levels showed that a significant part of the events identified by the independent devision hypothesis have the same structures and can be interpreted as fractals. Events reconstructed by the dependent devision hypothesis are suppressed.
This work analyzes the
method of fractals and various background events (mixed, random, and distributed according to Gauss’s law, as well as by power and exponential laws) in order to search and ...reconstruct fractal structures. It is shown that some of the background events are reconstucted as fractals. Dimensional distributions of various events are considered. It is found that these distributions for fractals and background events are different. Characteristics are proposed that describe the features of fractal structures. They are compared for fractals and background events. Criteria for background suppression are proposed and the results of their application are presented. It is found that the application of the criteria changes the distribution of background events by dimension, and the use of a combination of criteria suppresses the background.
The
and
methods are used for the fractal analysis of mixed events containing different types of complete and incomplete fractals and impurities. A procedure for analyzing incomplete fractals by the
...method and a technique for correction in determining the dimension
for fractals with a combined partition are proposed. It is found that the
method fully reconstructs incomplete fractals and suppresses the background, while the separation of fractals and background events using the
method depends on the base of fractal formation. It is shown that the
method reconstructs the distribution of fractals over dimension
more exactly than the
method.
An analysis of a data set containing fractals and background events is carried out using the method of the equation system of P-adic coverings (
SePaC
) and by the box-counting (
BC
) method. The ...peculiarities of these methods applied to the search for fractals in sets containing only fractals and background events are studied. Procedures allowing one to establish the presence of fractals, estimate their number in the initial set, separate fractals, and evaluate the portion of background events in the extracted set are suggested. A comparison of the result of an analysis of mixed events by these methods is carried out.
We report precision measurements of hypernuclei $^3_ΛH$ and $^4_ΛH$ lifetimes obtained from Au + Au collisions at $\sqrt{sNN}$ = 3.0 GeV and 7.2 GeV collected by the STAR experiment at the ...Relativistic Heavy Ion Collider, and the first measurement of $^3_ΛH$ and $^4_ΛH$ midrapidity yields in Au + Au collisions at $\sqrt{sNN}$ = 3.0 GeV. $^3_ΛH$ and $^4_ΛH$, being the two simplest bound states composed of hyperons and nucleons, are cornerstones in the field of hypernuclear physics. Their lifetimes are measured to be 221 ± 15 (stat) ± 19 (syst) ps for $^3_ΛH$ and 218 ± 6 (stat) ± 13 (syst) ps for $^4_ΛH$. The pT-integrated yields of $^3_ΛH$ and $^4_ΛH$ are presented in different centrality and rapidity intervals. It is observed that the shape of the rapidity distribution of $4_ΛH$ is different for 0%–10% and 10%–50% centrality collisions. Thermal model calculations, using the canonical ensemble for strangeness, describes the $^3_ΛH$ yield well, while underestimating the $^4_ΛH$ yield. Transport models, combining baryonic mean-field and coalescence (jam) or utilizing dynamical cluster formation via baryonic interactions (phqmd) for light nuclei and hypernuclei production, approximately describe the measured $^3_ΛH$ and $^4_ΛH$ yields. Our measurements provide means to precisely assess our understanding of the fundamental baryonic interactions with strange quarks, which can impact our understanding of more complicated systems involving hyperons, such as the interior of neutron stars or exotic hypernuclei.
The chiral magnetic effect (CME) refers to charge separation along a strong magnetic field due to imbalanced chirality of quarks in local parity and charge-parity violating domains in quantum ...chromodynamics. The experimental measurement of the charge separation is made difficult by the presence of a major background from elliptic azimuthal anisotropy. This background and the CME signal have different sensitivities to the spectator and participant planes, and could thus be determined by measurements with respect to these planes. We report such measurements in Au+Au collisions at a nucleon-nucleon center-of-mass energy of 200 GeV at the Relativistic Heavy-Ion Collider. It is found that the charge separation, with the flow background removed, is consistent with zero in peripheral (large impact parameter) collisions. Some indication of finite CME signals is seen with a significance of 1–3 standard deviations in mid-central (intermediate impact parameter) collisions. Furthermore, significant residual background effects may, however, still be present.
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