arXiv subjects

Gy. Wolf

Publications and source records attributed to Gy. Wolf.

25 records · Page 2Linked to original sources

arXiv2002

From meson- and photon-nucleon scattering to vector mesons in nuclear matter

We present a relativistic and unitary approach to pion- and photon-nucleon scattering taking into account the $πN$, $ρN$, $ωN$, $ηN$, $πΔ$, $K Λ$ and $K Σ$ channels. Our scheme dynamically generates the s- and d-wave nucleon resonances N(1535), N(1650), N(1520) and N(1700) and isobar resonances $Δ(1620)$ and $Δ(1700)$ in terms of quasi-local two-body interaction terms. We obtain a fair description of the experimental data relevant for slow vector-meson propagation in nuclear matter. The s-wave $ρ$- and $ω$-meson nucleon scattering amplitudes, which define the leading density modification of the $ρ$- and $ω$-meson spectral functions in nuclear matter, are predicted.

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arXiv2002

Production of phi mesons in subthreshold heavy-ion collisions

Within a BUU type transport model we study $ϕ$ meson production in subthreshold Ni+Ni and Ru+Ru reactions. For the first time we included in our model the elementary reaction channels $ρ+N,Δ\to ϕ+N$, $π+N(1520) \to ϕ+N$ and $πρ$ $\to$ $ϕ$. In spite of a substantial increase of the $ϕ$ multiplicities by these channels our results stay significantly below the preliminary experimental data.

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arXiv2002

Dilepton decays of baryon resonances

Dalitz decay of baryon resonances is studied and expressions for the decay width are derived for resonances with arbitrary spin and parity. Contributions of the various terms in the transition matrix element are compared and relevance of spin-parity and the resonance mass is discussed. Explicite algebraic expressions are cited for spin$\le$5/2 resonances. The results can be used in models of dielectron production in elementary reactions and heavy ion collisions.

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arXiv2002

Subthreshold phi-meson production in heavy-ion collisions

Within a transport code of BUU type the production of phi-mesons in the reactions Ni+Ni at 1.93 AGeV and Ru+Ru at 1.69 AGeV is studied. New elementary reaction channels rho+N(Delta) to phi+N and pi+N(1520) to phi+N are included. In spite of a substantial increase of the ϕmultiplicities by these channels the results stay below the tentative numbers extracted from experimental data.

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arXiv1997

Probing nuclear expansion dynamics with $π^-/π^+$-spectra

We study the dynamics of charged pions in the nuclear medium via the ratio of differential $π^-$- and $π^+$-spectra in a coupled-channel BUU (CBUU) approach. The relative energy shift of the charged pions is found to correlate with the pion freeze-out time in nucleus-nucleus collisions as well as with the impact parameter of the heavy-ion reaction. Furthermore, the long-range Coulomb force provides a 'clock' for the expansion of the hot nuclear system. Detailed comparisons with experimental data for $Au + Au$ at 1 GeV/A and $Ni + Ni$ at 2.0 GeV/A are presented.

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arXiv1996

Pion-Production in Heavy-Ion Collisions at SIS energies

We investigate the production of pions in heavy-ion collisions in the energy range of $1$ - $2$ GeV/A. The dynamics of the nucleus-nucleus collisions is described by a set of coupled transport equations of the Boltzmann-Uehling-Uhlenbeck type for baryons and mesons. Besides the $N(938)$ and the $Δ(1232)$ we also take into account nucleon resonances up to masses of $1.9 GeV/c^2$ as well as $π$-, $η$- and $ρ$-mesons. We study in detail the influence of the higher baryonic resonances and the $2π$-production channels ($NN\to NN ππ$) on the pion spectra in comparison to $π^-$ data from $Ar + KCl$ collisions at $1.8$ GeV/A and $π^0$-data for $Au+Au$ at 1.0 GeV/A. We, furthermore, present a detailed comparison of differential pion angular distributions with the BEVALAC data for Ar + KCl at 1.8 GeV/A. The general agreement obtained indicates that the overall reactions dynamics is well described by our novel transport approach.

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arXiv1993

Pion-nucleus reactions in a microscopic transport model

We analyse pion-nucleus reactions in a microscopic transport model of the BUU type, which propagates nucleons, pions, deltas and N(1440)-resonances explicitly in space and time. In particular we examine pion absorption and inelastic scattering cross sections for pion kinetic energies T(pi) =85-315MeV and various target masses. In general, the mass-dependence of the experimental data is well described for energies up to the delta-resonance (\approx 160 MeV) while the absorption cross sections are somewhat overestimated for the higher energies. In addition we study the possible dynamical effects of delta- and pion-potentials in the medium on various observables as well as alternative models for the in-medium delta-width.

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