Gyorgy Wolf
@wigner.hu
Theoretical Department
Wigner RCP
RESEARCH, TEACHING, or OTHER INTERESTS
Nuclear and High Energy Physics, Astronomy and Astrophysics
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Győző Kovács, Péter Kovács, György Wolf, Pok Man Lo, and Krzysztof Redlich
American Physical Society (APS)
Finite volume effects are studied both with low-momentum cutoff and with momentum discretization in the framework of an (axial)vector meson extended quark-meson model with Polyakov-loop variables. In the momentum cutoff scenario, the CEP moves to lower temperatures and larger quark chemical potentials as the characteristic system size is reduced, however, the treatment of the vacuum term significantly affects its trajectory. The size dependence of the baryon fluctuations is also studied by the kurtosis and the skewness, both of which show moderate dependence on temperature and some dependence on quark chemical potential. The order of the phase transition is also studied near the chiral limit at finite system size and found to be second-order only at vanishing explicit breaking. The implementation of the finite size effect with momentum discretization is more complicated and shows peculiar behavior due to the different modes dropping below the Fermi surface and strong dependence on the type of the boundary condition chosen. We found that both the different boundary conditions and the treatment of the vacuum term cause significant changes in the trajectory of the CEP as the characteristic system size is changed.
János Takátsy, Péter Kovács, György Wolf, and Jürgen Schaffner-Bielich
American Physical Society (APS)
The existence of quark matter inside the heaviest neutron stars has been the topic of numerous recent studies, many of them suggesting that a phase transition to strongly interacting conformal matter inside neutron stars is feasible. Here we examine this hybrid star scenario using a soft and a stiff hadronic model, a constituent quark model with three quark flavours, and applying a smooth crossover transition between the two. Within a Bayesian framework, we study the effect of up-to-date constraints from neutron star observations on the equation-of-state parameters and various neutron star observables. Our results show that a pure quark core is only possible if the maximum mass of neutron stars is below $\\sim2.35~M_\\odot$. However, we also find, consistently with other studies, that a peak in the speed of sound, exceeding $1/3$, is highly favoured by astrophysical measurements, which might indicate the percolation of hadrons at $\\sim3-4n_0$. Even though our prediction for the phase transition parameters varies depending on the specific astrophysical constraints utilized, the position of the speed of sound peak only changes slightly, while the existence of pure quark matter below $\\sim4 n_0$, using our parameterization, is disfavoured. On the other hand, the preferred range for the EoS shows signs of conformality above $\\sim4n_0$. Additionally, we present the difference in the upper bounds of radius estimates using the full probability density data and sharp cut-offs, and stress the necessity of using the former.
Sergei P. Maydanyuk, Gyorgy Wolf, and Kostiantyn A. Shaulsky
MDPI AG
(1) Purpose: Conditions of formation of compound nuclear systems needed for synthesis of heavy nuclei in pycnonuclear reactions in compact stars are studied on a quantum mechanical basis. (2) Methods: The method of multiple internal reflections is applied for pycnonuclear reactions in compact stars with new calculations of quasibound spectra and spectra of zero-point vibrations. (3) Results: Peculiarities of the method are analyzed for reaction with isotopes of Carbon. The developed method takes into account continuity and conservation of quantum flux (describing pycnonuclear reaction) inside the full spacial region of reaction, including the nuclear region. This gives the appearance of new states (called quasibound states) in which compound nuclear systems of Magnesium are formed with the largest probability. These states have not been studied yet in synthesis of elements in stars. Energy spectra of zero-point vibrations and spectra of quasibound states are estimated with high precision for reactions with isotopes of Carbon. For the first time, the influence of plasma screening on quasibound states and states of zero-point vibrations in pycnonuclear reactions has been studied. (4) Conclusions: The probability of formation of a compound nucleus in quasibound states in pycnonuclear reaction is essentially larger than the probability of formation of this system in states of zero-point vibrations studied by Zel’dovich and followers. Therefore, synthesis of Magnesium from isotopes of Carbon is more probable through the quasibound states than through the states of zero-point vibrations in compact stars. Energy spectra of zero-point vibrations are changed essentially after taking plasma screening into account. Analysis shows that from all studied isotopes of Magnesium, only 24Mg is stable after synthesis at an energy of relative motion of 4.881 MeV of the incident nuclei 12C.
János Takátsy, Péter Kovács, György Wolf, and Jürgen Schaffner‐Bielich
Wiley
AbstractThe equation of state provided by effective models of strongly interacting matter should comply with the restrictions imposed by current astrophysical observations on compact stars. We explore the possibility, that there is quark matter in the center of neutron stars. For the equation of state of the neutron star matter, we use a relativistic mean field model for the hadronic one and the (axial‐)vector meson extended linear sigma model for the quark phase. We assume that the transition is a cross‐over between these phases. We connect the two branches in this cross‐over regime continuously by a polynomial. This equation of state should comply with the restrictions imposed by current astrophysical observations on compact stars. Our model has four free parameters that should be fitted to experimental data. By using a Bayesian analysis, we found that our model could explain all the experimental constraints; furthermore, we have obtained the most probable parameter set for our model.
Gábor Balassa and György Wolf
Springer Science and Business Media LLC
AbstractIn this paper, the usual momentum- and coordinate-space distance criteria for creating nuclear clusters in transport simulations are readdressed by using a dynamical, covariant description in an off-shell Boltzmann-Uehling-Uhlenbeck transport approach. The free parameter of this clustering scheme is the cluster formation time, which is fitted through the FOPI data of low energy charged cluster multiplicities in Au+Au collisions at 150 A MeV, and 400 A MeV incident energies. The coalescence model is used to estimate the yields of the $$^3$$ 3 H$$_\\Lambda $$ Λ , $$^5$$ 5 H$$_{\\Lambda \\Lambda }$$ Λ Λ , $$^6$$ 6 He$$_{\\Lambda \\Lambda }$$ Λ Λ single and double strange hypernuclei in central Au+Au collisions between 2, and 20 A GeV incident energies, giving comparable results to estimations from other methods.
Péter Kovács, János Takátsy, Jürgen Schaffner-Bielich, and György Wolf
American Physical Society (APS)
The existence of quark matter inside the cores of heavy neutron stars is a possibility which can be probed with modern astrophysical observations. We use an (axial)vector meson extended quarkmeson model to describe quark matter in the core of neutron stars. We discover that an additional parameter constraint is necessary in the quark model to ensure chiral restoration at high densities. By investigating hybrid star sequences with various parameter sets we show that low sigma meson masses are needed to fulfill the upper radius constraints, and that the maximum mass of stable hybrid stars is only slightly dependent on the parameters of the crossover-type phase transition. Using this observation and results from recent astrophysical measurements a constraint of 2.6 < gV < 4.3 is set for the constituent quark – vector meson coupling. The effect of a nonzero bag constant is also investigated and we observe that its effect is small for values adopted in previous works.
Gábor Balassa and György Wolf
Springer Science and Business Media LLC
AbstractInclusive production cross sections of the possible exotic state X(3872) in proton–proton, pion-proton and proton–antiproton collisions are calculated using a statistical based model, which is previously used to describe inclusive charmed and bottomed hadron production cross sections in the low energy region. With the extensions made here the model is capable to include tetraquarks as well, using the diquark picture of tetraquarks. The evaluated cross section ratio of $$\\varPsi (2S)$$ Ψ ( 2 S ) and X(3872) at $$\\sqrt{s}=7$$ s = 7 TeV agrees well with the measured value.
GYORGY WOLF, GABOR BALASSA, and SU HOUNG LEE
WORLD SCIENTIFIC
János Takátsy, Péter Kovács, and György Wolf
Wiley
AbstractThe equation of state provided by effective models of strongly interacting matter should comply with the restrictions imposed by current astrophysical observations on compact stars. Using the equation of state given by the (axial‐)vector meson extended linear sigma model, we determine the mass–radius relation and study whether these restrictions are satisfied under the assumption that most of the star is filled with quark matter. We study the dependence of the mass–radius relation on the parameters of the model.
T. Ablyazimov, R.P. Adak, A. Adler, A. Agarwal, K. Agarwal, Z. Ahammed, A. Ahmad, F. Ahmad, N. Ahmad, A. Akindinov,et al.
Elsevier BV
Gábor Balassa and György Wolf
Springer Science and Business Media LLC
AbstractIn this work, we extended our statistical model with charmed and bottomed hadrons, and fit the quark creational probabilities for the heavy quarks, using low energy inclusive charmonium and bottomonium data. With the finalized fit for all the relevant types of quarks (up, down, strange, charm, bottom) at the energy range from a few GeV up to a few tens of GeV’s, the model is now considered complete. Some examples are also given for proton–proton, pion–proton, and proton–antiproton collisions with charmonium, bottomonium, and open charm hadrons in the final state.
Gábor Balassa and György Wolf
Springer Science and Business Media LLC
AbstractHadronic cross sections are important ingredients in many of the ongoing research methods in high energy nuclear physics, and it is always important to measure and/or calculate the probabilities of different types of reactions. In heavy-ion transport simulations at a few GeV energies, these hadronic cross sections are essential and so far mostly the exclusive processes are used, however, if one interested in total production rates the inclusive cross sections are also necessary to know. In this paper, we introduce a statistical-based method, which is able to give good estimates to exclusive and inclusive cross sections as well in the energy range of a few GeV. The method and its estimates for not well-known cross sections, will be used in a Boltzmann-Uehling-Uhlenbeck (BUU) type off-shell transport code to explain charmonium and bottomonium mass shifts in heavy-ion collisions.
János Takátsy, Péter Kovács, Zsolt Szép, and György Wolf
MDPI AG
The equation of state provided by effective models of strongly interacting matter should comply with the restrictions imposed by current astrophysical observations of compact stars. Using the equation of state given by the (axial-)vector meson extended linear sigma model, we determine the mass–radius relation and study whether these restrictions are satisfied under the assumption that most of the star is filled with quark matter. We also compare the mass–radius sequence with those given by the equations of state of somewhat simpler models.
Miklós Zétényi and György Wolf
Elsevier BV
László B. Szabados and György Wolf
Springer Science and Business Media LLC
György Wolf, Gábor Balassa, Péter Kovács, Miklós Zétényi, and Su Houng Lee
Elsevier BV
Miklós Zétényi and György Wolf
EDP Sciences
We study the production of the doubly strange Ξ baryon in subthreshold p + A collisions using a BUU type transport model. We propose a new mechanism for Ξ creation in a two-step process via hyperon-nucleon collisions. We study the influence of the anisotropy of hyperon production in N + N collisions on the Ξ multiplicity. Applying reasonable assumptions on the unknown elementary cross sections, we are able to reconstruct the Ξ yield observed by the HADES collaboration (GSI, Darmstadt) in subthreshold p+Nb collisions.
Gábor Balassa, Péter Kovács, and György Wolf
Springer Science and Business Media LLC
Gy. Wolf, G. Balassa, P. Kovács, M. Zétényi, and S.H. Lee
Jagiellonian University
We study the excitation function of the low-lying charmonium state: $\\Psi$(3686) in $\\bar p$ Au collisions taking into account their in-medium propagation. The time evolution of the spectral functions of the charmonium state is studied with a BUU type transport model. We calculated the excitation function of $\\Psi$(3686) production and show that it is strongly effected by the medium. The energy regime will be available for the PANDA experiment.
T. Ablyazimov, A. Abuhoza, R. P. Adak, M. Adamczyk, K. Agarwal, M. M. Aggarwal, Z. Ahammed, F. Ahmad, N. Ahmad, S. Ahmad,et al.
Springer Science and Business Media LLC
Gy. Wolf, G. Balassa, P. Kovács, M. Zétényi, and S.H. Lee
Jagiellonian University
We study the in-medium propagation of low-lying charmonium states: $J/\\Psi$, $\\Psi$(3686), and $\\Psi$(3770) in a $\\bar p$ Au $10$ GeV collision. This energy regime will be available for the PANDA experiment. The time evolution of the spectral functions of the charmonium states is studied with a BUU type transport model. We observe a substantial effect of the medium in the dilepton spectrum.
P. Kovács and Gy. Wolf
Jagiellonian University
In the framework of the $N_f = 2+1$ flavor (axial)vector meson extended Polyakov quark meson model we investigate the QCD phase diagram at finite temperature and density. We use a $\\chi^2$ minimization procedure to parameterize the model based on tree\\,-\\,level decay widths and vacuum scalar and pseudoscalar curvature masses which incorporate the contribution of the constituent quarks. Using a hybrid approximation (mesons at tree level, fermions at one\\,-\\,loop level) for the grand potential we determine the phase boundary both on the $\\mu_B-T$ and $\\rho-T$ planes. We also determine the location of the critical end point of the phase diagram. Moreover by calculating the pressure and other thermodynamical quantities derived from it, we determine a set of isentropic curves in the crossover region. We show that the curves behave very similarly as their counterparts obtained from the lattice in the crossover regime.
Gy. Wolf and P. Kovács
Jagiellonian University
We investigate the chiral phase transition of the strongly interacting matter at nonzero temperature and baryon chemical potential $\\mu_B$ within an extended (2+1) flavor Polyakov constituent quark-meson model which incorporates the effect of the vector and axial vector mesons. The parameters of the model are determined by comparing masses and tree-level decay widths with experimental values. We examine the restoration of the chiral symmetry by monitoring the temperature evolution of condensates. We study the $T-\\rho_B$ phase diagram of the model and find that a critical end point exists, although at very low density.
György Wolf and Miklós Zétényi
Springer Science and Business Media LLC