Latest documents http://publikationen.ub.uni-frankfurt.de/index/index/ Fri, 14 Jul 2006 10:15:10 +0200 Fri, 14 Jul 2006 10:15:10 +0200 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2382 An investigation of the transition to delta matter is performed based on a relativistic mean field formulation of the nonlinear sigma and omega model. We demonstrate that in addition to the Delta-meson coupling, the occurrence of the baryon resonance isomer also depends on the nucleon-meson coupling. Our results show that for the favored phenomenological value of m* and K, the Delta isomer exists at baryon density ~ 2–3 p0 if beta=1.31 is adopted. For universal coupling of the nucleon and Delta, the Delta density at baryon density ~ 2–3 p0 and temperature ~ 0.4–0.5 fm-1 is about normal nuclear matter density, which is in accord with a recent experimental finding. Zhuxia Li; Guangjun Mao; Yizhong Zhuo; Walter Greiner article http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/2382 Fri, 14 Jul 2006 10:15:10 +0200 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/3048 A self-consistent relativistic integral-di erential equation of the Boltzmann- Uehling-Uhlenbeck-type for the N*(1440) resonance is developed based on an effective Lagrangian of baryons interacting through mesons. The closed time-path Green s function technique and semi-classical, quasi-particle and Born approxima- tions are employed in the derivation. The non-equilibrium RBUU-type equation for the N*(1440) is consistent with that of nucleon s and delta s which we derived before. Thus, we obtain a set of coupled equations for the N,Delta and N*(1440) distribution functions. All the N (1440)-relevant in-medium two-body scattering cross sections within the N,Delta and N*(1440) system are derived from the same effective Lagrangian in addition to the mean field and presented analytically, which can be directly used in the study of relativistic heavy-ion collisions. The theoreticalprediction of the free pp - pp* (1440) cross section is in good agreement with the experimental data. We calculate the in-medium N+N - N+N* , N* +N - N+N and N*+N - N* +N cross sections in cold nuclear matter up to twice the nuclear matter density. The influence of different choices of the N* N* coupling strengths, which can not be obtained through fitting certain experimental data, are discussed. The results show that the density dependence of predicted in-medium cross sections are sensitive to the N* N* coupling strengths used. An evident density dependence will appear when a large scalar coupling strength of g^(sigma) N*N* is assumed. PACS number(s): 24.10.Cn; 25.70.-z; 21.65.+f Guangjun Mao; Ludwig Neise; Horst Stöcker; Walter Greiner; Zhuxia Li preprint http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/3048 Wed, 21 Dec 2005 11:00:59 +0100