M. Zétényi

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. Explicit algebraic expressions are cited for spin ≤5/2 resonances. The results can be used in models of dielectron production in elementary reactions and heavy ion collisions.

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.

Propagation of spectral functions and dilepton production at SIS energies

The time evolution of vector meson spectral functions is studied within a BUU-type transport model. Applications focus on ρ and ω mesons being important pieces for the interpretation of the dielectron invariant mass spectrum. Since the evolution of the spectral functions is driven by the local density, the inmedium modifications turn out to compete, in this approach, with the known vacuum contributions.

Calculations of K± and ϕ production in near-threshold proton-nucleus collisions

K± and ϕ meson 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 target mass dependence of ϕ production is predicted to give important information on the in-medium properties of all three mesons.

Off-shell transport of broad resonances and dilepton production at SIS energies

The time evolution of vector meson spectral functions is studied within a Boltzmann-Uehling-Uhlenbeck (BUU) type transport model. Applications focus on ρ and ω mesons being important pieces for the interpretation of the dielectron invariant mass spectrum. Since the evolution of the spectral functions is driven by the local density, the in-medium modifications turn out to compete, in this approach, with the known vacuum contributions.

Subthreshold ϕ meson production in 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 → Φ + N, π + N((1520) → Φ + N and πρ → Φ. In spite of a substantial increase of the Φ multiplicities by these channels, our results stay significantly below the preliminary experimental data.Within a BUU type transport model we study

Production of phi mesons in subthreshold heavy-ion collisions

\phi

Subthreshold φ meson production in heavy-ion collisions

meson production in subthreshold Ni+Ni and Ru+Ru reactions. For the first time we included in our model the elementary reaction channels

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

\rho+N,\Delta \to \phi+N

Charmonium Excitation Functions in

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