Centrality in Relativistic Nuclear Collisions and the Random Matrix Approach

Using the random matrix approach,results for nearest-neighbor distributions obtained from experimental data on ^(12)C+^(12)C collisions at 4.2 A GeV/c and simulations produced with the aid of an ultra-relativistic quantum molecular dynamics model are studied.Comparison reveals that the observed changes in the nearest-neighbor distributions for different multiplicities can be associated with the onset of a region of central collisions.

Coherent nonlinear structures in dense electron positron plasma

It is shown that rarefactive-type double layer structures exist in ultradense electron-positron plasma.For this purpose,an extended Korteweg de Vries equation is derived and solved analytically in the low amplitude limit by employing the appropriate fluid equations.A strong influence of quantum degeneracy pressure of electrons and positrons,quantum diffraction effects and concentration of background positive ions on double layer is noticed.It is also pointed out that the amplitude and steepness of the double layer increases with an increase in ion concentration or ion charge number.The results are examined numerically for some interesting cases of dense plasmas with illustrations.

Model Predictions of Charged-Particle Azimuthal Distributions and Forward-Backward Correlations in pp Interactions at s1/2= 900 GeV

We report inelastic interactions of protons at the center of mass energy s1/2 = 900 Ge V, by using different event generators to study the forward-backward(FB) correlation in summed transverse momentum and multiplicity of produced charged particles. The transverse momentum, p T ≥ 100 Me V, and pseudorapidity, | η |< 2.5, have been employed for both the correlations. The simulation results are compared with the ATLAS experimental data, obtained with the same values of | η | and p T at s1/2 = 900 Ge V. We also measure the jet and jet-like structure as a function of azimuthal distributions in the events relative to the highest transverse momentum particle. Three overlapping regions of pseudorapidity, | η |< 1.0, | η |< 2.0, and | η |< 2.5 are used with transverse momentum, p T > 500 Me V. For FB correlations, EPOS, and Sybill2.3 c results are in a good agreement with the data as compared to the other models.Similarly, for the azimuthal distribution, EPOS-LHC, DPMJETIII, and Sibyll2.3 c show good agreement with the data for full η region. In general, EPOS provides a better description of the data for both the quantities studied in this paper.

Analysis of shower particle pseudorapidity spectra in interactions of relativistic Au and Pb ions with emulsion nuclei

The pseudorapidity spectra of fast particles （with β 〉 0.7） produced in Au （at 11.6 A GeV） and Pb （at 158 A GeV） induced collisions with emulsion （Em） nuclei contain some visual plateaus and shoulders. The plateau is wider for Pb＋Em reactions compared with the Au＋Em ones. The existence of a plateau is expected for parton models. The Fourier transformation and maximum entropy methods were used to get additional information about the plateaus. The dependence of the plateaus on the centrality of the collisions was also studied using the number of g-particles to fix centrality. It shows that the maximum entropy method could confirm the existence of the plateau and the shoulder on distributions.

Centrality of the collision and random matrix theory

I discuss the results from a study of the central ^12CC collisions at 4.2 A GeV/c. The data have been analyzed using a new method based on the Random Matrix Theory. The simulation data coming from the Ultra Relativistic Quantum Molecular Dynamics code were used in the analyses. I found that the behavior of the nearest neighbor spacing distribution for the protons, neutrons and neutral pions depends critically on the multiplicity of secondary particles for simulated data. I conclude that the obtained results offer the possibility of fixing the centrality using the critical values of the multiplicity.

Central nucleus-nucleus collisions at relativistic energies with a new method based on Random Matrix Theory

Using the method based on Random Matrix Theory （RMT）, the results for the nearest-neighbor distributions obtained from the experimental data on ^12C-C collisions at 4.2 AGeV/c have been discussed and compared with the simulated data on ^12C-C collisions at 4.2 AGeV/c produced with the aid of the Dubna Cascade Model. The results show that the correlation of secondary particles decreases with an increasing number of charged particles Nch. These observed changes in the nearest-neighbor distributions of charged particles could be associated with the centrality variation of the collisions.