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Gy. Wolf

Publications and source records attributed to Gy. Wolf.

At least 19 recordsLinked to original sources
arXiv2019

Charmonium Excitation functions in $\bar p$A Collisions

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.

hep-ph↗
arXiv2017

Mass shift of charmonium states in $\bar p A$ collision

The masses of the low lying charmonium states, namely, the $J/\Psi$, $\Psi(3686)$, and $\Psi(3770)$ are shifted downwards due to the second order Stark effect. In $\bar p + \text{Au}$ collisions at $6-10$ GeV we study their in\,-\,medium propagation. The time evolution of the spectral functions of these charmonium states is studied with a Boltzmann\,-\,Uehling\,-\,Uhlenbeck (BUU) type transport model. We show that their in\,-\,medium mass shift can be observed in the dilepton spectrum. Therefore, by observing the dileptonic decay channel of these low lying charmonium states, especially for $\Psi(3686)$, we can gain information about the magnitude of the gluon condensate in nuclear matter. This measurement could be performed at the upcoming PANDA experiment at FAIR.

hep-ph↗
arXiv2017

The phase diagram in the vector meson extended linear sigma model

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.

hep-ph↗
arXiv2017

Charmonium spectral functions in $\bar p A$ collision

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.

nucl-th↗
arXiv2014

Chiral phase transition in an extended linear sigma model: initial results

We investigate the scalar meson mass dependence on the chiral phase transition in the framework of an SU(3), (axial)vector meson extended linear sigma model with additional constituent quarks and Polyakov loops. We determine the parameters of the Lagrangian at zero temperature in a hybrid approach, where we treat the mesons at tree-level, while the constituent quarks at 1-loop level. We assume two nonzero scalar condensates and together with the Polyakov-loop variables we determine their temperature dependence according to the 1-loop level field equations.

hep-ph↗
arXiv2012

Phenomenology of light mesons within a chiral approach

The so-called extended linear sigma model is a chiral model with (pseudo)scalar and (axial-)vector mesons. It is based on the requirements of (global) chiral symmetry and dilatation invariance. The purpose of this model is the description of the hadron phenomenology up to 1.7 GeV. We present the latest theoretical results, which show a good agreement with the experiment.

hep-ph↗
arXiv2012

Scalar mesons in a linear sigma model with (axial-)vector mesons

The structure of the scalar mesons has been a subject of debate for many decades. In this work we look for $\bar{q}q$ states among the physical resonances using an extended Linear Sigma Model that contains scalar, pseudoscalar, vector, and axial-vector mesons both in the non-strange and strange sectors. We perform global fits of meson masses, decay widths and amplitudes in order to ascertain whether the scalar $\bar{q}q$ states are below or above 1 GeV. We find the scalar states above 1 GeV to be preferred as $\bar{q}q$ states.

hep-ph↗
arXiv2010

Chiral symmetry, di-electrons and charm

We survey some prospects of identifying further in-medium modifications of hadrons in a strongly interacting medium with respect to ongoing experiment series of the HADES Collaboration and planned experiments of the CBM Collaboration at FAIR. Di-electrons, strange and charm mesons are considered and their potential for signaling imprints of chiral restoration is highlighted.

nucl-th↗
arXiv2009

Role of phi decays for K- yields in relativistic heavy-ion collisions

The production of strange mesons in collisions of Ar+KCl at a kinetic beam energy of 1.756 AGeV is studied within a transport model of Boltzmann-Ühling-Uhlenbeck (BUU) type. In particular, $ϕ, K^+$ and $K^-$ yields and spectra are compared to the data mesured recently by the HADES collaboration and the $ϕ$ yield measured previously by the FOPI collaboration. Our results are in agreement with these data thus presenting an interpretation of the subleading role of $ϕ$ decays into $K^-$'s and confirming the importance of the strangeness-exchange channels for $K^-$ production.

nucl-th↗
arXiv2009

Propagation of vector-meson spectral-functions in a BUU type transport model: Application to di-electron production

The time evolution of vector-meson spectral-functions is studied within a kinetic theory approach. We implement this formalism in a BUU type transport model. Applications focus on rho and omega mesons being important pieces for the interpretation of the di-electron invariant mass spectrum measured by the HADES collaboration for the reaction C + C at 2 AGeV bombarding energy. Since the evolution of the spectral functions is driven by the local density, the in-medium modifications are tiny for small collision systems within this approach.

nucl-th↗
arXiv2005

Transport Theories for Heavy Ion Collisions in the 1 AGeV Regime

We compare multiplicities as well as rapidity and transverse momentum distributions of protons, pions and kaons calculated within presently available transport approaches for heavy ion collisions around 1 AGeV. For this purpose, three reactions have been selected: Au+Au at 1 and 1.48 AGeV and Ni+Ni at 1.93 AGeV.

nucl-th↗
arXiv2004

Calculations of K+, K- and phi Production in Near-Threshold Proton-Nucleus Collisions

K+, K- and ϕmeson production in proton-nucleus (pA) collisions has been calculated within a BUU transport model. It is shown that the nucleon-hyperon strangeness transfer channel is essential. The role of three-body reactions has been investigated within the medium. The targetmass dependence of $ϕ$ production is predicted to give important information on the in-medium properties of all three mesons.

nucl-th↗
arXiv2003

Probing in-medium vector meson decays by double-differential di-electron spectra in heavy-ion collisions at SIS energies

Within a transport code simulation for heavy-ion collisions at bombarding energies around 1 AGeV, we demonstrate that double-differential di-electron spectra with suitable kinematical cuts are useful to isolate (i) the $ρ$ meson peak even in case of strong broadening, and (ii) the in-medium $ω$ decay contribution. The expected in-medium modifications of the vector meson spectral densities can thus be probed in this energy range via the di-electron channel.

nucl-th↗
arXiv2003

Baryonic contributions to the dilepton spectrum of nucleon-nucleon collisions

We study the production of dileptons in relativistic nucleon-nucleon collisions. Additionally to the traditional dilepton production channels (vector meson decays, meson and Delta(1232) Dalitz decays) we included in our model as new dilepton sources the Dalitz decay of higher unflavored baryon resonances with spin<=5/2 and mass<=2.25 GeV/c^2. The contributions of these new channels are estimated using experimental information about the Ngamma decays of the resonances and have large uncertainties. The obtained dilepton spectra are compared to the experimental data by the DLS collaboration. Predictions for the HADES detector (SIS, GSI) are also discussed. In spite of the large uncertainties of the higher resonance Dalitz decay contributions we are able to draw the conclusion that these contributions are negligible compared to the other dilepton sources and do not influence the detectability of the phi and omega vector meson peaks.

nucl-th↗
arXiv2002

Scattering of vector mesons off nucleons

We construct a relativistic and unitary approach to 'high' energy pion- and photon-nucleon reactions taking the $πN, πΔ$, $ρN$, $ωN$, $ηN, K Λ, K Σ$ final states into account. Our scheme dynamically generates the s- and d-wave nucleon resonances N(1535), N(1650) and N(1520) and isobar resonances $Δ(1620)$ and $Δ(1700)$ in terms of quasi-local interaction vertices. The description of photon-induced processes is based on a generalized vector-meson dominance assumption which directly relates the electromagnetic quasi-local 4-point interaction vertices to the corresponding vertices involving the $ρ$ and $ω$ fields. We obtain a satisfactory description of the elastic and inelastic pion- and photon-nucleon scattering data in the channels considered. The resulting s-wave $ρ$- and $ω$-nucleon scattering amplitudes are presented. Using these amplitudes we compute the leading density modification of the $ρ$ and $ω$ energy distributions in nuclear matter. We find a repulsive energy shift for the $ω$ meson at small nuclear density but predict considerable strength in resonance-hole like $ω$-meson modes. Compared to previous calculations our result for the $ρ$-meson spectral function shows a significantly smaller in-medium effect. This reflects a fairly small coupling strength of the N(1520) resonance to the $ρN$ channel.

nucl-th↗
arXiv2002

Evaluation of QCD sum rules for HADES

QCD sum rules are evaluated at finite nucleon densities and temperatures to determine the change of pole mass parameters for the lightest vector mesons $ρ$, $ω$ and $ϕ$ in a strongly interacting medium at conditions relevant for the starting experiments at HADES. The role of the four-quark condensate is highlighted. A few estimates (within a fire ball model and BUU calculations) of dilepton spectra in heavy-ion collisions at 1 AGeV are presented.

nucl-th↗
arXiv2002

Neutron star properties with in-medium vector mesons

We explore the impact of in-medium modification of the properties of vector mesons on the nuclear equation of state and neutron star properties. It is found that in-medium modifications stiffen the nuclear equation of state considerably. If this feature has its correspondence in the full treatment of dense hadronic matter, then very little room is left for the existence of exotic phases like quark matter or boson condensates in the centers of neutron stars of canonical mass.

nucl-th↗