arXiv subjects

A. S. Sorin

Publications and source records attributed to A. S. Sorin.

At least 37 records · Page 2Linked to original sources

arXiv2013

Systematic properties of the Tsallis Distribution: Energy Dependence of Parameters in High-Energy p-p Collisions

Changes in the transverse momentum distributions with beam energy are studied using the Tsallis distribution as a parameterization. The dependence of the Tsallis parameters q, T and the volume are determined as a function of beam energy. The Tsallis parameter q shows a weak but clear increase with beam energy with the highest value being approximately 1.15. The Tsallis temperature and volume are consistent with being independent of beam energy within experimental uncertainties.

hep-ph↗

arXiv2013

Bruhat Order in Full Symmetric Toda System

In this paper we discuss some geometrical and topological properties of the full symmetric Toda system. We show by a direct inspection that the phase transition diagram for the full symmetric Toda system in dimensions $n=3,4$ coincides with the Hasse diagram of the Bruhat order of symmetric groups $S_3$ and $S_4$. The method we use is based on the existence of a vast collection of invariant subvarieties of the Toda flow in orthogonal groups. We show how one can extend it to the case of general $n$. The resulting theorem identifies the set of singular points of $\mathrm{dim}=n$ Toda flow with the elements of the permutation group $S_n$, so that points will be connected by a trajectory, if and only if the corresponding elements are Bruhat comparable. We also show that the dimension of the submanifolds, spanned by the trajectories connecting two singular points, is equal to the length of the corresponding segment in the Hasse diagramm. This is equivalent to the fact, that the full symmetric Toda system is in fact a Morse-Smale system.

nlin.SI↗

arXiv2012

Adiabatic Chemical Freeze-out and Wide Resonance Modification in a Thermal Medium

Here we develop a model equation of state which successfully parameterizes the thermodynamic functions of hadron resonance gas model at chemical freeze-out and which allows us to naturally explain the adiabatic chemical freeze-out criterion. The present model enables us to clearly demonstrate that at chemical freeze-out the resulting hadronic mass spectrum used in the hadron resonance gas model is not an exponential-like, but a power-like. We argue that such a property of hadronic mass spectrum at chemical freeze-out can be explained by the two new effects found here for wide resonances existing in a thermal environment: the near threshold thermal resonance enhancement and the near threshold resonance sharpening. The effect of resonance sharpening is studied for a sigma meson and our analysis shows that for the temperatures well below 92 MeV the effective width of sigma meson is about 50 to 70 MeV. Thus, the effect of resonance sharpening justifies the usage of the sigma-like field-theoretical models for the strongly interacting matter equation of state at such temperatures. Also we argue that the most optimistic hope to find the quark gluon bags experimentally may be related to their sharpening and enhancement in a thermal medium. In this case the wide quark gluon bags may appear directly or in decays as narrow resonances that are absent in the tables of elementary particles and that have the width about 50-150 MeV and the mass about or above 2.5 GeV.

hep-ph↗

arXiv2012

Critical exponents of the quark-gluon bags model with the critical endpoint

The critical indices α', β, γ' and δof the Quark Gluon Bags with Surface Tension Model that has the critical endpoint are calculated and compared with the exponents of other models. These indices are expressed in terms of the most general parameters of the model. Despite the usual expectations the found critical indices do not depend on the Fisher exponent τand on the parameter \varkappa which relates the mean bag surface to its volume. The scaling relations for the obtained critical exponents are verified and it is demonstrated that for the standard definition of the index α' the Fisher and the Griffiths scaling inequalities are not fulfilled in general case, whereas the Liberman scaling inequality is always obeyed. This is not surprising for the phase diagram with the asymmetric properties of pure phases, but the present model also provides us with the first and explicit example that the specially defined index α'_s does not recover the scaling relations as well. Therefore, here we suggest the physically motivated definition of the index α' = α'_c and demonstrate that such a definition recovers the Fisher scaling inequality, while it is shown that the Griffiths inequality should be generalized for the phase diagram with the asymmetric properties. The critical exponents of several systems that belong to different universality classes are successfully described by the parameters of the present model and hence its equation of state can be used for a variety of practical applications.

nucl-th↗

arXiv2012

Observation of the E(38)-boson

The first results of the search for the E(38)-boson are presented. The search was conducted in the effective mass spectra of photon pairs produced in the d(2.0 GeV/n) + C, d(3.0 GeV/n) + Cu and p(4.6 GeV) + C reactions. The experimental data was obtained at internal beams of the JINR Nuclotron. Due to non ordinariness of the obtained results (standing out of The Standard Model) and at the request of co-authors the first version of the article is withdrawn for further verification and more detailed description of the experiment and data analysis. The second version is being prepared.

hep-ex↗

arXiv2012

Simple Solution to the Strangeness Horn Description Puzzle

We propose to use the thermal model with the multi-component hard-core radii to describe the hadron yield ratios from the low AGS to the highest RHIC energies. It is demonstrated that the variation of the hard-core radii of pions and kaons enable us to drastically improve the fit quality of the measured mid-rapidity data and for the first time to completely describe the Strangeness Horn behavior as the function of the energy of collision without spoiling the fit quality of other ratios. The best global fit is found for the vanishing hard-core radius of pions and for the hard-core radius of kaons being equal to 0.35 fm, whereas the hard-core radius of all other mesons is fixed to 0.3 fm and that one of baryons is fixed to 0.5 fm. It is argued that the multi-component hadron resonance gas model opens us a principal possibility to determine the second virial coefficients of hadron-hadron interaction.

hep-ph↗

arXiv2012

Resonance structure in the γγ and $π^0π^0$ systems in dC interactions

Along with $π^0$ and η mesons, a resonance structure in the invariant mass spectrum of two photons at Mγγ = 360 \pm 7 \pm 9 MeV is observed in the reaction d + C \rightarrow γ + γ + X at momentum 2.75 GeV/c per nucleon. Estimates of its width and production cross section are Γ = 64 \pm 18 MeV and $σ_{γγ}$ = 98 \pm 24 μb, respectively. The collected statistics amount to 2339 \pm 340 events of 1.5 \cdot 10^6 triggered interactions of a total number ~ 10^12 of dC-interactions. The results on observation of the resonance in the invariant mass spectra of two $π^0$ mesons are presented: the data obtained in the d + C \rightarrow γ + γ reaction is confirmed by the d + C \rightarrow $π^0$ + $π^0$ reaction: $M_{π^0π^0}$ = 359.2 \pm 1.9 MeV, Γ = 48.9 \pm 4.9 MeV; the ratio of Br(R\rightarrowγγ) / Br(R\rightarrow$π^0π^0$) = (1.8 ÷ 3.7)\cdot10^-3.

nucl-ex↗

arXiv2011

Physical mechanism of the (tri)critical point generation

We discuss some ideas resulting from a phenomenological relation recently declared between the tension of string connecting the static quark-antiquark pair and surface tension of corresponding cylindrical bag. This relation analysis leads to the temperature of vanishing surface tension coefficient of the QGP bags at zero baryonic charge density as T_σ= 152.9 +- 4.5 MeV. We develop the view point that this temperature value is not a fortuitous coincidence with the temperature of (partial) chiral symmetry restoration as seen in the lattice QCD simulations. Besides, we argue that T_σdefines the QCD (tri)critical endpoint temperature and claim that a negative value of surface tension coefficient recently discovered is not a sole result, but should also exist in ordinary liquids at the supercritical temperatures.

hep-ph↗

arXiv2011

Can We Rigorously Define Phases in a Finite System?

Here we propose the generalized statistical multifragmentation model which includes the liquid phase pressure of the most general form. This allows us to get rid of the absolute incompressibility of the nuclear liquid. Also the present model employes a very general form the surface tension coefficient of nuclear fragments. Such a model is solved analytically for finite volumes by the Laplace-Fourier transform method to isobaric ensemble. A complete analysis of the isobaric partition singularities of this model is also 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 to exactly define the finite volume analogs of gaseous, liquid and mixed phases of the class of similar models from the first principles of statistical mechanics and demonstrate the pitfalls of earlier works. The finite width effects for large nuclear fragments and quark gluon bags are also discussed.

nucl-th↗

arXiv2011

Directed, Elliptic and Triangular Flows in Asymmetric Heavy Ion Collisions

In this paper we propose to thoroughly investigate asymmetric nuclear collisions both in the fixed target mode at the laboratory energy below 5 GeV per nucleon and in the collider mode with a center of mass energy below 11 GeV per nucleon. Using the UrQMD transport model, we demonstrate a strong enhancement of directed and elliptic flow coefficients for the midcentral asymmetric nuclear collisions compared to symmetric collisions. We argue that such an enhancement is due to the disappearance of the nuclear shadowing effect on the side of the smaller projectile nucleus. An analysis of the energy and centrality dependencies of the directed, elliptic and triangular flows at midrapidity shows us their sensitivity to the details of the employed model of hadronic interaction. In general, the flow patters found for asymmetric nuclear collisions have a very rich and complicated structure of energy and centrality dependencies compared to the flows found for symmetric collisions and are worth to be investigated experimentally. The directed, elliptic, and triangular flow coefficients are computed for target nuclei containing high density fluctuations and thoroughly compared with that ones obtained in the absence of such fluctuations.

nucl-th↗

arXiv2011

Dynamical and thermal descriptions in parton distribution functions

We suggest a duality between the standard (dynamical) and statistical distributions of partons in the nucleons. The temperature parameter entering into the statistical form for the quark distributions is estimated. It is found that this effective temperature is practically the same for the dependence on longitudinal and transverse momenta and, in turn, it is close to the freeze-out temperature in high energy heavy-ion collisions.

hep-ph↗

arXiv2011

Brane solutions and integrability: a status report

We review the status of the integrability and solvability of the geodesics equations of motion on symmetric coset spaces that appear as sigma models of supergravity theories when reduced over respectively the timelike and spacelike direction. Such geodesic curves describe respectively timelike and spacelike brane solutions. We emphasize the applications to black holes.

hep-th↗

arXiv2010

Asymptotic Regge Trajectories of Non-strange Mesons

We analyze the asymptotic behavior of Regge trajectories of non-strange mesons. In contrast to an existing belief, it is demonstrated that for the asymptotically linear Regge trajectories the width of heavy hadrons cannot linearly depend on their mass. Using the data on masses and widths of rho_J, omega_J, a_J and f_J mesons for the spin values J \leq 6, we extract the parameters of the asymptotically linear Regge trajectory predicted by the finite width model of quark gluon bags. As it is shown the obtained parameters for the data set B correspond to the cross-over temperature lying in the interval 170.9-175.3 MeV which is consistent with the kinetic freeze-out temperature of early hadronizing particles found in relativistic heavy ion collisions at and above the highest SPS energy.

hep-ph↗

arXiv2010

Black holes in supergravity and integrability

Stationary black holes of massless supergravity theories are described by certain geodesic curves on the target space that is obtained after dimensional reduction over time. When the target space is a symmetric coset space we make use of the group-theoretical structure to prove that the second order geodesic equations are integrable in the sense of Liouville, by explicitly constructing the correct amount of Hamiltonians in involution. This implies that the Hamilton-Jacobi formalism can be applied, which proves that all such black hole solutions, including non-extremal solutions, possess a description in terms of a (fake) superpotential. Furthermore, we improve the existing integration method by the construction of a Lax integration algorithm that integrates the second order equations in one step instead of the usual two step procedure. We illustrate this technology with a specific example.

hep-th↗

arXiv2010

Duality of thermal and dynamical descriptions in particle interactions

We suggest a duality between the statistical and standard (dynamical) distributions of partons in the nucleons. The temperature parameter entering into the statistical form for the quark distributions is estimated. It is found that this effective temperature is practically the same for the dependence on logitudinal and transverse momenta and, it is close to the freeze-out temperature in high energy heavy-ion collisions.

hep-ph↗

arXiv2009

Resonance Structure in the $γγ$ Invariant Mass Spectrum in $p$C- and $d$C-Interactions

Along with $π^0$ and $η$ mesons, a resonance structure in the invariant mass spectrum of two photons at $M_{γγ}= 360 \pm 7 \pm 9$ MeV is observed in the reaction $d C\toγ+ γ+X$ at momentum 2.75 GeV/c per nucleon. Estimates of its width and production cross section are $Γ= 63.7 \pm 17.8$ MeV and $σ_{γγ}=98\pm24^{+93}_{-67} {\rm μb}$, respectively. The collected statistics amount to $2339 \pm 340$ events of $1.5\cdot 10^6$ triggered interactions of a total number $\sim 10^{12}$ of $d$C-interactions. This resonance structure is not observed in $p$C collisions at the beam momentum 5.5 GeV/c. Possible mechanisms of this ABC-like effect are discussed.

nucl-ex↗

arXiv2009

Thermal Effects for Quark and Gluon Distributions in Heavy-Ion Collisions

In-medium effects for distributions of quarks and gluons in central A+A collisions are considered. We suggest a duality principle, which means similarity of thermal spectra of hadrons produced in heavy-ion collisions and inclusive spectra which can be obtained within the dynamic quantum scattering theory. Within the suggested approach we show that the mean square of the transverse momentum for these partons grows and then saturates when the initial energy increases. It leads to the energy dependence of hadron transverse mass spectra which is similar to that observed in heavy ion collisions.

nucl-th↗

arXiv2008

Transverse momentum spectra of hadrons produced in central heavy-ion collisions

In-medium effects of transverse-mass distributions of quarks and gluons are considered assuming a possible local equilibrium for colorless quark objects like mesons and baryons created in central A+A collisions. It is shown that the average square of the transverse momentum for these partons grows and then saturates when the initial energy increases. Within the quark-gluon string model it leads to the energy dependence of hadron transverse mass spectra which is similar to that observed in heavy ion collisions. Comparison with other scenarios is given.

nucl-th↗