The collective behavior of the partons and its influence on the jet suppression in heavy ion collisions

We discuss the physical picture that a parton interaction with a coherent group of partons can lead to more jet quenching effect in the hot and dense matter created by heavy ion collisions at RHIC and LHC energies. We came to this picture after analyzing the behaviour of the nuclear modification factor as a function of $p_T$ for the charged particles produced in the most central Pb-Pb collisions at 2.76 A TeV. In the interval, $7-50 GeV/c$ the values of the factor as a function of $p_T$ increases almost linearly with a slope is very close to expected one for the inverse Compton effect. Around $p_T\simeq 60$ GeV/c, a regime change occurs, which is characteristic for the phenomenon. We propose that this similarity can be explained by the inverse Compton effect for partons, which occurs via a collective parton group formation ( through the appearance of a new string as a result of the fusion of strings) and its interactions with single partons in the interval of $5 < p_T < 10 GeV/c$. In the case of a coherent collision with a parton that has a lower energy than the group, the parton can gain energy through the inverse Compton effect, resulting in its acceleration and shifting to the region of $p_T >10$ GeV/c. After losing a significant part of its energy new string will decay into partons with lower energies - slowed partons in the interval of $p_T < 5 GeV/c$. This enhancement in the jet quenching can be observed in the interval of $2 <p_T <20 GeV/c$.Comment: 8 pages, 1 figure, 1 tabl

Entropy and multifractal analysis of multiplicity distributions from pp simulated events up to LHC energies

Using three different Monte Carlo generators of high energy proton-proton collisions (HIJING, NEXUS, and PSM) we study the energy dependence of multiplicity distributions of charged particles including the LHC energy range. Results are used for calculation of the information entropy, Renyi's dimensions and other multifractal characteristics of particle production.Comment: 15 pages, 8 figure

On some inverse problems in nuclear physics

Some inverse problems in high-energy physics, neutron diffraction and NMR spectroscopy are discussed. To solve them, the Fourier integrated transformation method and the Maximum Entropy Technique (MENT) were used. The integrated images of experimental distributions are shown to be informative when determining the space-time parameters of a particle generation zone and when analysing blurred spectra. The efficiency of the above methods was checked by comparing relevant results with the results obtained independently

The maximum entropy tecniques and the statistical description of systems

The maximum entropy technique (MENT) is used to determine the distribution functions of physical values. MENT naturally combines required maximum entropy, the properties of a system and connection conditions in the form of restrictions imposed on the system. It can, therefore, be employed to statistically describe closed and open systems. Examples in which MENT is used to describe equilibrium and non-equilibrium states, as well as steady states that are far from being in thermodynamic equilibrium, are discussed

Search for periodicities in experimental data using an autoregression data model

To process data obtained during interference experiments in high-energy physics, methods of spectral analysis are employed. Methods of spectral analysis, in which an autoregression model of experimental data is used, such as the maximum entropy technique as well as Pisarenko and Prony's method, are described. To show the potentials of the methods, experimental and simulated hummed data are discussed as an example

Searching for the properties of nuclear matter using proton-carbon and deuteron-carbon collisions at 4.2 a gev/c

The present work reports the use of nuclear transparency effect of protons in proton and deuteron carbon interactions at 4.2 A GeV/c to get information about the states of nuclear matter. The half angle technique is used to extract the information on nuclear transparency. The results are compared with Dubna version of Cascade model. The average values of multiplicity, momentum and transverse momentum of protons are analyzed as a function of the number of identified protons in an event. We observed some evidence and trends in the data which could be considered as transparency effect. Analysis of the results shows that the leading effect is the basis of the observed transparency. Some contribution to the observed effect could be the existing short range correlations and the scaling power law s^-N, for exclusive two body hard scattering.Comment: 7 pages, 2 figure

The meaning behind observed pTp_T regions at the LHC energies

We argue that $p_T$ distribution data from the LHC on the invariant differential yield of the charged primary particles in $pp$ collisions at $\sqrt{s}=0.9 TeV, 2.76 TeV,7TeV$ and in $Pb-Pb$ collisions at $\sqrt{s_{NN}}=2.76 TeV$ with 6 centrality bins contains several $p_T$ regions with special properties. These distributions were analysed by fitting the data with exponential functions. We conclude that the regions reflect features of fragmentation and hadronization of partons through the string dynamics. The nuclear transparency results in negligible influence of the medium in the III region ($p_T >17-20 GeV/c$), which has highest $p_T$ values. The effects and changes by the medium start to appear weakly in the II region ($4-6 GeV/c < p_T< 17-20 GeV/c$) and become stronger in the I region ($p_T <4-6 GeV/c$) . It seems that the II region has highest number of strings. The increase in string density in this region could lead to fusion of strings, appearance of a new string and collective behaviour of the partons in the most central collisions. These phenomena can explain anomalous behaviour of the Nuclear Modification Factor in the II region. We propose the II region as a possible area of Quark Gluon Plasma formation through string fusion. The first $p_T$ regions are the ones with the maximum number of hadrons and minimum number of strings due to direct hadronization of the low energy strings into two quark systems - mesons.Comment: 20 pages with 10 figures and 3 table

Search for a Signal on Phase Transitions of Strongly Interacting Matter using the Nuclear Transparency Effect

We discuss that the results coming from the central experiments confirm the results which had been obtained for the behavior of the K+-meson's temperature behavior as a function of the energy in SPS energy range. To see the "horn" for the behavior of the ratio for average values of K+- to pi+- mesons as a function of centrality the new more rich experimental data are required. The data can be obtained with NICA/MPD setup. The existing of the QCD critical point could be identified by using the nuclear transparency effect as a function of the centrality.Comment: 6 pages, 5 figure

Spectral spacing correlations of nucleus-nucleus collisions at high energies

We propose a novel approach to the analysis of experimental data obtained in relativistic nucleus-nucleus collisions which borrows from methods developed within the context of Random Matrix Theory. It is applied to the detection of correlations in momentum distributions of emitted particles. We find good agreement between the results obtained in this way and a standard analysis based on the two-pair correlation function often used in high energy physics. The method introduced here is free from unwanted background contributions.Comment: 5 pages, 4 figure

Study of some characteristics of protons using interactions of light nuclei

Behavior of some average characteristics of protons are studied in protons and deuterons induced interactions with carbon nuclei at 4.2 A GeV/c. The emitted particles are divided in two groups depending on their polar angle in the lab. frame using half angle technique. Results of the experimental data are compared with Dubna version of cascade model. Analysis of the results show that the incone protons are leading particles.Comment: 7 pages, 1 caption figur