### Regular Series

#### Vol. 48 (2017), No. 2, pp. 109 – 228

Forward–Backward Multiplicity Correlations at the LHC from Independent Sources

Acta Phys. Pol. B 48, 113 (2017)

page 113 •

abstract

It is argued that the superposition approach, where partons are independently emitted from longitudinally extended sources in the early stage, is fully compatible with the experimental results for the forward–backward multiplicity correlations in Pb+Pb collisions at $\sqrt {s_{NN}}=2.76$ TeV. The pertinent correlation analysis is based on the Ph.D. Thesis by I. Sputowska which includes an unpublished analysis of data taken by the ALICE Collaboration. Our calculations show that in the experimentally covered pseudorapidity range $\Delta \eta =1.2$, the initial sources in the backward and forward bins are maximally correlated, which complies to the string-like interpretation of the underlying early-stage production mechanism.

Thermodynamics and Kinetics of Gribov–Zwanziger Plasma with Temperature-dependent Gribov Parameter

Acta Phys. Pol. B 48, 125 (2017)

page 125 •

abstract

A Gribov-type dispersion relation is treated as an effective description of interacting gluons forming a hot medium. Temperature dependence of the Gribov parameter is determined from the fit to the lattice Yang–Mills results describing thermodynamic functions. To maintain thermodynamic consistency of the approach, a temperature-dependent bag pressure is introduced. The results obtained for equilibrium functions are generalised in the next step to non-equilibrium conditions. We derive formulas for the bulk and shear viscosity coefficients within the relaxation time approximation. We find evidence for largely enhanced bulk viscosity in the region of the phase transition.

Vortex Solutions in the Abelian Higgs Model with a Neutral Scalar

Acta Phys. Pol. B 48, 145 (2017)

page 145 •

abstract

We construct an extension of the Abelian Higgs model, which consists of a complex scalar field by including an additional real, electromagnetically neutral scalar field. We couple this real scalar field to the complex scalar field via a quartic coupling and investigate U(1) vortex solutions in this “extended Abelian Higgs model”. Since this model has two additional homogeneous ground states, the U(1) vortices that can form in this model have a richer structure than in the Abelian Higgs model. We also find the “phase diagram” of the model showing the parameter space in which the real scalar particle condenses in the vortex state while having a zero vacuum expectation value in the homogeneous ground state.

Production of the Doubly Heavy Baryons, $B_c$ Meson and the All-charm Tetraquark at AFTER@LHC with Double Intrinsic Heavy Mechanism

Acta Phys. Pol. B 48, 163 (2017)

page 163 •

abstract

In the paper, we discuss contribution of the doubly intrinsic heavy mechanism into the production of $B_c$ meson, the doubly heavy baryons and the all-charm tetraquark at a future fixed-target experiment at the LHC (AFTER@LHC). The production cross sections and the mean values of Feynman-$x$ for the final states are presented.

Can the Massive Neutron Star PSR J0348+0432 be a Hyperon Star?

Acta Phys. Pol. B 48, 171 (2017)

page 171 •

abstract

Whether the massive neutron star PSR J0348+0432 can change into a hyperon star is studied in the framework of the relative mean-field theory by choosing the suitable hyperon coupling constants. We find that notwithstanding the mesons $\sigma ^{*}$ and $\phi$ are considered or not, the neutron star PSR J0348+0432 can all change into a hyperon star and the hyperon star transition density are the same for the two cases. We also find that the canonical mass neutron star can also change into a hyperon star in a minor hyperon star transition density as the mesons $\sigma ^{*}$ and $\phi$ are not considered. Our results confirm some of recent conclusions.

Nuclear Matter Incompressibility: From VMC to Skyrme–Landau Parameterization

Acta Phys. Pol. B 48, 183 (2017)

page 183 •

abstract

The new Skyrme parameter set is determined by requiring that Variational Monte Carlo (VMC) calculations reproduce empirical values for properties of nuclear matter, such as binding energy per particle and saturation density. We found the new Landau parameter set by using the new Skyrme parameter set, the saturation density, and energy obtained from the new Skyrme parameter set for symmetric nuclear matter (SNM). Incompressibility of symmetric nuclear matter is also calculated by the described Skyrme–Landau Parameterization.

Liquid-gas Phase Transition in Hot Asymmetric Matter with NL3*

Acta Phys. Pol. B 48, 195 (2017)

page 195 •

abstract

The liquid-gas phase transition of asymmetric nuclear matter is studied within the relativistic mean-field model with nonlinear isoscalar–isovector coupling. The density dependence of symmetry energy constrained from the measured neutron skin thickness of finite nuclei has also been used in the investigation. It is found that several features of liquid-gas phase transition, such as, liquid-gas coexistence region, critical values of pressure and isospin asymmetry and maximal isospin asymmetry increase with the softness of density dependence of symmetry energy. It is also found that the critical temperature is higher for softer symmetry energy.

BTW Model with Probabilistically Nonuniform Distribution of Particles Coming from the Unstable Sites

Acta Phys. Pol. B 48, 207 (2017)

page 207 •

abstract

The two-dimensional BTW model of SOC, with probabilistically nonuniform distribution of particles among the (nearest) neighbouring sites, is studied by the computer simulation. When the value of height variable of a particular site reaches the critical value ($z_{\rm c}=4$), the value of height variable of that site is reduced by four units by distributing four particles among the four nearest neighbouring sites. In this paper, it is considered that two particles are distributed equally among the two nearest neighbouring sites along $x$-axis. However, the distribution of other two particles along $y$-axis, is probabilistically nonuniform. The variation of spatial average of the height variable with time is studied. In the SOC state, the distributions of avalanche sizes and durations are obtained. The total number of topplings occurred during the stipulated time of evolution is also calculated.

The Generalized Uncertainty Principle and the Stark Effect

Acta Phys. Pol. B 48, 217 (2017)

page 217 •

abstract

In a series of papers, Kempf and his collaborators Mangano and Mann presented a D-dimensional ($\beta , \beta ^{\prime }$)-two-parameter deformed Heisenberg algebra which leads to a non-zero minimal length. In this work, according to generalized uncertainty principle (GUP), the electrostatic field in the presence of a minimal length scale based on the Kempf algebra is studied in the special case of $\beta ^{\prime }=2\beta$ up to the first order over the deformation parameter $\beta$. We use modified electrostatic field and then we find the Stark potential in the presence of a minimal length. An upper limit for the polarizability in the presence of a measurable length is obtained. Also, the modified energy shifts in the ground state and excited states of hydrogen atom is found. We estimate the isotropic minimal length. The estimation is close to the minimal observable distance which was proposed by Heisenberg ($\ell _{0}\sim 10^{-13}$ cm).

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