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Larissa V. Bravina

Publications and source records attributed to Larissa V. Bravina.

9 recordsLinked to original sources
arXiv2025

Coalescence production of sexaquark with three diquarks in high-energy nuclear collisions

The coalescence production of sexaquark, a hypothetical stable state with quark content $(uuddss)$, is investigated by the parton and hadron cascade model PACIAE in $pp$ collisions at $\sqrt s = 7$ TeV. In this work, the compact sexaquark bound state of three diquarks is formed in the final partonic state by a two-step approach, which involves ``diquark" formation via partonic coalescence and sexaquark construction with dynamically constrained phase-space coalescence model successively. The yields, yield ratios, and dependences of spatial parameters (the size of diquark $D_{0}$ and the radius of sexaquark $R_{0}$) of (anti-)sexaquark are predicted. The yields of a hadronic molecule H-dibaryon $\mathrm{H}(ΛΛ)$ generated in the final hadronic state are also compared. These estimates provide references for future sexaquark searches and other exotic state studies, such as dibaryons.

hep-ph↗
arXiv2024

A Brief Introduction to PACIAE 4.0

Parton And-hadron China Institute of Atomic Energy (PACIAE) is a multipurpose Monte Carlo event generator developed to describe a wide range of high-energy collisions, including lepton-lepton, lepton-hadron, lepton-nucleus, hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions. It is built based on the PYTHIA program, and incorporates parton and hadron cascades to address the nuclear medium effects. PACIAE 4.0 is the new generation of PACIAE model surpassing the version 3.0. In PACIAE 4.0, the old fixed-format FORTRAN 77 code has been refactored and rewritten by the free-format modern Fortran and C++ languages. The C++-based PYTHIA 8.3 is interfaced in, while previous versions connected to the Fortran-based PYTHIA 6.4 only. Several improvements are also introduced, which enable PACIAE 4.0 to contain more physics and features to model the high-energy collisions. This is the first attempt to transition PACIAE from Fortran to C++.

hep-ph↗
arXiv2023

Initial Vorticities of Quark-Gluon Matter in Heavy-ion Collisions

We calculate four types of initial vorticities in Au+Au collisions at energies $ \sqrt{S_{NN}} $ = 5--200 GeV using a microscopic transport model PACIAE. Our simulation shows the non-monotonic dependence of the initial vorticities on the collision energies. The energy turning point is around 10-15 GeV for different vorticities but not sensitive to impact parameter.

nucl-th↗
arXiv2019

The concept of induced surface and curvature tensions and a unified description of the gas of hard discs and hard spheres

Mathematically rigorous derivation of the hadron matter equation of state within the induced surface and curvature tensions approach is worked out. Such an equation of state allows one to go beyond the Van der Waals approximation for the interaction potential of hard spheres. The compressibility of a single- and two-component hadron mixtures are found for two- and three-dimensional cases. The obtained results are compared to the well known one- and two-component equations of state of hard spheres and hard discs. The values of the model parameters which successfully reproduce the above-mentioned equations of state on different intervals of packing fractions are determined from fitting their compressibility factors. It is argued that after some modification the developed approach can be also used to describe the mixtures of gases of convex hard particles of different sizes and shapes.

nucl-th↗
arXiv2011

All-loop calculation of the Reggeon field theory amplitudes via stochastic model

The evolution equations for Green functions of the Reggeon Field Theory (RFT) are equivalent to those of the inclusive distributions for the reaction-diffusion system of classical particles. We use this equivalence to obtain numerically Green functions and amplitudes of the RFT with all loop contributions included. The numerical realization of the approach is described and some important applications including total and elastic proton--proton cross sections are studied. It is shown that the loop diagram contribution is essential but can be imitated in the eikonal cross section description by changing the Pomeron intercept. A role of the quartic Pomeron coupling which is an inherent part of the stochastic model is shown to be negligible for available energies.

hep-ph↗
arXiv1998

Statistical prefactor and nucleation rate near and out of the critical point

The nucleation rate derived in the classical theory contains at least one undetermined parameter, which may be expressed in terms of the Langer first-principles theory. But the uncertainties in the accounting for fluctuation modes, which are either absorbed into the free energy of a critical cluster or not, result in different evaluations of the statistical prefactor and nucleation rate. We get the scaling approximations of the nucleation rate for the vapour condensation both near and out of the critical range. The results obtained deserve the experimental verification to resolve the theoretical uncertainty. PACS numbers: 64.60.Qb, 05.70.Fh, 64.60.Fr, 64.70.Fx

cond-mat.stat-mech↗
arXiv1998

Homogeneous nucleation: Comparison between two theories

The classical nucleation theory of Becker, Döring and Zeldovich is compared with the Langer coarse-grained field approach to the nucleation phenomenon. Both formalisms have been applied to the condensation from a supersaturated vapor. It is shown that the nucleation rate derived in the classical theory can be expressed in a form equivalent to that of the field nucleation theory. This equivalence serves as an explanation of the puzzling fact that the numerical predictions of both theories for condensation of Xe and CO$_2$ are almost identical though the standard analytical expressions for the nucleation rates are different. The results obtained can help to link the theories of nucleation and their approximations.

cond-mat.dis-nn↗
arXiv1998

Determination of nucleation rates near the critical point

The nucleation rates derived for the condensation from a supersaturated vapor are examined both in the classical theory and in the modern coarse-grained field theory. By virtue of the scaling variable $λ_Z$ it is shown that the method of steepest descent is irrelevant to evaluate the nucleation rate in the proximity of the critical point in the capillary approximation. If the logarithmic corrections to the activation energy of a droplet are taken into account, then the calculated nucleation rates provide an adequate description of the liquid-gas phase transition both near and out of the critical range.

cond-mat.dis-nn↗