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Kyrill A. Bugaev

Publications and source records attributed to Kyrill A. Bugaev.

15 recordsLinked to original sources
arXiv2022

Colliding and Fixed Target Mode in a Single Experiment -- A Novel Approach to Study the Matter under New Extreme Conditions

Here, we propose a novel approach to experimentally and theoretically study the properties of QCD matter under new extreme conditions, namely having an initial temperature over 300~MeV and baryonic charge density over three times the values of the normal nuclear density. According to contemporary theoretical knowledge, such conditions were not accessible during the early Universe evolution and are not accessible now in the known astrophysical phenomena. To achieve these new extreme conditions, we proposed performing high-luminosity experiments at LHC or other colliders by means of scattering the two colliding beams at the nuclei of a solid target that is fixed at their interaction region. Under plausible assumptions, we estimate the reaction rate for the p+C+p and Pb+Pb+Pb reactions and discuss the energy deposition into the target and possible types of fixed targets for such reactions. To simulate the triple nuclear collisions, we employed the well-known UrQMD 3.4 model for the beam center-of-mass collision energies 2.76 TeV. As a result of our modeling, we found that, in the most central and simultaneous triple nuclear collisions, the initial baryonic charge density is approximately three times higher than the one achieved in the ordinary binary nuclear collisions at this energy.

hep-ph↗
arXiv2020

Alternative Formulation of the Induced Surface and Curvature Tensions Approach

We develop a novel method to analyze the excluded volume of the multicomponent mixtures of classical hard spheres in the grand canonical ensemble. The method is based on the Laplace-Fourier transform technique and allows one to account for the fluctuations of the particle number density for the induced surface and curvature tensions equation of state. As a result one can go beyond the Van der Waals approximation by obtaining the suppression of the induced surface and curvature tensions coefficients at moderate and high packing fractions. In contrast to the standard induced surface and curvature tensions equation of state the suppression of these coefficients is not an exponential one, but a power-like one. The obtained alternative equation of state is further generalized to account for higher virial coefficients. This result is straightforwardly generalized to the case of quantum statistics.

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arXiv2020

Bose-Einstein Condensation of Quantum Hard-Spheres as a Deposition Phase Transition and New Relations Between Bosonic and Fermionic Pressures

We investigate the phase transition of Bose-Einstein particles with the hard-core repulsion in the grand canonical ensemble within the Van der Waals approximation. It is shown that the pressure of non-relativistic Bose-Einstein particles is mathematically equivalent to the pressure of simplified version of the statistical multifragmentation model of nuclei with the vanishing surface tension coefficient and the Fisher exponent $τ_F = \frac{5}{2}$, which for such parameters has the 1-st order phase transition. The found similarity of these equations of state allows us to show that within the present approach the high density phase of Bose-Einstein particles is a classical macro-cluster with vanishing entropy at any temperature which, similarly to the classical hard spheres, is a kind of solid state. To show this we establish new relations which allow us to identically represent the pressure of Fermi-Dirac particles in terms of pressures of Bose-Einstein particles of two sorts.

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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.

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arXiv2010

Equation of State and Phase Transitions in the Nuclear and Hadronic Systems

An investigation of strongly interacting matter equation of state remains one of the major tasks of modern high energy nuclear physics for almost a quarter of century. The present work is my doctor of science thesis which contains my contribution (42 works) to this field made between 1993 and 2008. Inhere I mainly discuss the common physical and mathematical features of several exactly solvable statistical models which describe the nuclear liquid-gas phase transition and the deconfinement phase transition. Luckily, in some cases it was possible to rigorously extend the solutions found in thermodynamic limit to finite volumes and to formulate the finite volume analogs of phases directly from the grand canonical partition. It turns out that finite volume (surface) of a system generates also the temporal constraints, i.e. the finite formation/decay time of possible states in this finite system. Among other results I would like to mention the calculation of upper and lower bounds for the surface entropy of physical clusters within the Hills and Dales model; evaluation of the second virial coefficient which accounts for the Lorentz contraction of the hard core repulsing potential between hadrons; inclusion of large width of heavy quark-gluon bags into statistical description. I believe that the suggested mathematical solution of the freeze-out problem in relativistic hydrodynamic model and in hydro-cascade model has not only an academic interest, but also has some practical value. In addition I hope that the experience gained in working out some partly successful signals of deconfinement transition can be useful for other researchers to go further in this direction.

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arXiv2009

Testing the Influence of Surface Tension and Finite Width of QGP Bags on the QCD Matter EOS Properties at NICA Energies

Here I give some strong arguments that the central issues for theoretical studies of the (tri)critical endpoint of the QCD phase diagram are the surface tension of large/heavy QGP bags and their medium dependent width. Then I discuss three major directions to further develop the realistic exactly solvable statistical models which simultaneously are able to describe the 1-st order deconfinement phase transition, the 2-nd order one and the cross-over. Also I analyze the most necessary projects that have to be studied in order to formulate the reliable and convincing signals of the mixed phase formation at NICA energies.

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arXiv2008

The Van-der-Waals Gas EOS for the Lorentz Contracted Spheres

The relativistic equation of state (EOS) of the Van-der-Waals gas is suggested and analyzed. In contrast to the usual case, the Lorentz contraction of the sphere's volume is taken into account. It is proven that the suggested EOS obeys the causality in the limit of high densities, i.e., the value of sound velocity of such a media is subluminar. The pressure obtained for the high values of chemical potential has an interesting kinetic interpretation. The suggested EOS shows that for high densities the most probable configuration corresponds to the smallest value of the relativistic excluded volume. In other words, for high densities the configurations with the collinear velocities of the neighboring hard core particles are the most probable ones. This, perhaps, may shed light on the coalescence process of any relativistic hard core constituents.

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arXiv2007

Exactly Solvable Model for the QCD Tricritcal Endpoint

An inclusion of temperature and chemical potential dependent surface tension into the gas of quark-gluon bags model resolves a long standing problem of a unified description of the first and second order phase transition with the cross-over. The suggested model has an exact analytical solution and allows one to rigorously study the vicinity of the critical endpoint of the deconfinement phase transition. It is found that at the curve of a zero surface tension coefficient there must exist the surface induced phase tranition of the 2-nd or higher order. The present model predicts that the critical endpoint (CEP) of quantum chromodynamics is the tricritical endpoint.

hep-ph↗
arXiv2006

Yield scalings of clusters with fewer than 100 nucleons

This document gives a historical review of the scaling of particles yields emitted from excited nuclei. The focus will be on what scaling is, what can be learned from scaling, the underlying theory of why one might expect particle yields to scale, how experimental particle yields have been observed to scale, model systems where particle (cluster) yields do scale and finally scaling observed in the particle yields of various low and medium energy nuclear reaction experiments. The document begins with a basic introduction to scaling in the study of critical phenomena and then reviews Fisher's theory which has all the aspects of scaling and can be directly applied to the counting of clusters, the most reliable measurement accessible to the experimental study of nuclear reactions. Also this document gives a history of the various scalings observed in nuclear reaction experiments and culminates with an estimate of the nuclear liquid-vapor phase boundary based upon measured particle yields.

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arXiv2005

Exact Analytical Solution of the Constrained Statistical Multifragmentation Model and Phase Transitions in Finite Systems

We discuss an exact analytical solution of a simplified version of the statistical multifragmentation model with the restriction that the largest fragment size cannot exceed the finite volume of the system. A complete analysis of the isobaric partition singularities of this model is done for finite volumes. It is shown that the real part of any simple pole of the isobaric partition defines the free energy of the corresponding state, whereas its imaginary part, depending on the sign, defines the inverse decay/formation time of this state. The developed formalism allows us, for the first time, to exactly define the finite volume analogs of gaseous, liquid and mixed phases of this model from the first principles of statistical mechanics and demonstrate the pitfalls of earlier works. The finite size effects for large fragments and the role of metastable (unstable) states are discussed.

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arXiv2004

Exact Analytical Solution of the Constrained Statistical Multifragmentation Model

A novel powerful mathematical method is presented, which allows us to find an analytical solution of a simplified version of the statistical multifragmentation model with the restriction that the largest fragment size cannot exceed the finite volume of the system. A complete analysis of the isobaric partition singularities is done for finite system volumes. The finite size effects for large fragments and the role of metastable (unstable) states are discussed.

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arXiv2003

Hadronic correlations above the chiral/deconfinement transition

The statistical bootstrap model is critically revised in order to include a medium-dependent resonance width in it. We show that a thermodynamic model with a vanishing width below the Hagedorn temperature T_H and a Hagedorn spectrum-like width above T_H may not only eliminate the divergence of the thermodynamic functions above T_H, but also gives a satisfactory description the lattice quantum chromodynamics (QCD) data on the energy density above the chiral/deconfinement transition as the main result of this contribution. This model allows to explain the absence of heavy resonance contributions in the fit of the experimentally measured particle ratios at SPS and RHIC energies.

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arXiv2002

Transverse Momentum Spectra of $J/ψ$ and $ψ^{\prime}$ Mesons from Quark Gluon Plasma Hadronization at CERN SPS

A popular derivation of the apparent temperature of the particle transverse momentum spectra and its inconsistency are considered. An improved formula for the apparent temperature is discussed. It is shown that recent results on transverse mass spectra of $J/ψ$ and $ψ^{\prime}$ mesons support a hypothesis of statistical production of charmonia at hadronization and suggest the early thermal freeze-out of these mesons. Using the apparent temperature formula the collective transverse velocity of the hadronizing quark gluon plasma is extracted to be $ \approx 0.2$. Predictions for transverse mass spectra of hidden and open charm mesons along with bottomonium at SPS and RHIC energies are discussed.

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arXiv1999

Shock-like Freeze-out in Relativistic Hydrodynamics

We have formulated a self-consistent model of freeze-out on an arbitrary hypersurface. It conserves energy and momentum across the discontinuity between ideal fluid and the gas of free particles. Energy and momentum of those free particles have non-equilibrium values that could be a signal for the formation of hot and dense matter in heavy ion collisions.

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