Miklós Zétényi

Three-flavor chiral effective model with four baryonic multiplets within the mirror assignment

We study three-flavor octet baryons by using the so-called extended Linear Sigma Model (eLSM). Within a quark-diquark picture, the requirement of a mirror assignment naturally leads to the consideration of four spin- ½ baryon multiplets. A reduction of the Lagrangian to the two-flavor case leaves four doublets of nucleonic states which mix to form the experimentally observed states N(939), N(1440), N(1535) and N(1650). We determine the parameters of the nucleonic part of the Lagrangian from a fit to masses and decay properties of the aforementioned states. By tracing their masses when chiral symmetry is restored, we conclude that the pairs N(939), N(1535) and N(1440), N(1650) form chiral partners.

Dilepton production in pion-nucleon collisions in an effective field theory approach

We present a model of electron-positron pair production in pion-nucleon collisions in the exclusive reaction \pi N -> Ne^+e^-. The model is based on an effective field theory approach, incorporating 16 baryon resonances below 2 GeV. Parameters of the model are fitted to pion photoproduction data. We present the resulting dilepton invariant mass spectra for \pi^- p collisions up to sqrt(s)=1.9 GeV center-of-mass collision energy. These results are meant to give predictions for the planned experiments at the HADES spectrometer in GSI, Darmstadt.

Mass shift of charmonium states in p¯A collision

Abstract The masses of the low lying charmonium states, namely, the J / Ψ , Ψ ( 3686 ) , and Ψ ( 3770 ) are shifted downwards due to the second order Stark effect. In p ¯ + 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 Ψ ( 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.

Baryonic channels of dilepton production

A calculation of the Dalitz-decay width of baryon resonances is presented and applied to dilepton production in proton-proton collisions in the BEVALAC/SIS energy range. The results indicate, that for these energies the contribution of Dalitz decay of higher baryon resonances (i.e. other that the δ(1232)) are negligible.

Influence of anisotropic Λ/Σ creation on the Ξ− multiplicity in subthreshold proton–nucleus collisions

Abstract We present an analysis of Ξ − baryon production in subthreshold proton–nucleus ( p + A ) collisions in the framework of a BUU type transport model. We propose a new mechanism for Ξ production in the collision of a secondary Λ or Σ hyperon and a nucleon from the target nucleus. We find that the Ξ − multiplicity in p + A collisions is sensitive to the angular distribution of hyperon production in the primary N + N collision. Using reasonable assumptions on the unknown elementary cross sections we are able to reproduce the Ξ − multiplicity and the Ξ − / ( Λ + Σ 0 ) ratio obtained in the HADES experiment in p+Nb collisions at s N N = 3.2 GeV energy.

Dilepton and

Abstract.We argue that the NICA fixed-target experiment will be able to provide very important new experimental data on dilepton and

\phi

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meson production in elementary and nuclear collisions at the NICA fixed-target experiment

meson production in the basically undiscovered energy domain between the SIS and SPS energies. Experimental information about elementary cross sections in this energy region is an essential ingredient of models of nuclear collisions in the same energy range.

Baryon octet and decuplet phenomenology in a three-flavor extended linear sigma model

We present an effective model, which is an extension of the usual linear sigma model, that contains a low energy multiplet for every hadronic particle type. These multiplets are a scalar nonet, a pseudoscalar nonet, a vector nonet, an axialvector nonet, a baryon octet and a baryon decuplet. Tree level baryon masses and possible two body decuplet decays are calculated. The baryon masses are generated through spontaneous symmetry breaking. The calculated quantities are used to determine the model parameters through a multiparametric minimalization process, which compares the calculated physical quantities with their experimental values. We found that the calculated quantities are in good agreement with the experimental data.