1,722 research outputs found

    Near-threshold production of a0(980) mesons in the reaction pp -> d K^+ \bar{K}^0

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    Using an effective Lagrangian approach as well as the Quark-Gluon Strings Model we analyze near-threshold production of a0(980)-mesons in the reaction NN -> d K \bar{K} as well as the background of non-resonant K\bar{K}-pair production. We argue that the reaction pp -> d K^+ \bar{K}^0 at an energy release Q<=100 MeV is dominated by the intermediate production of the a0(980)-resonance. At larger energies the non-resonant K^+\bar{K}^0-pair production - where the kaons are produced in a relative P-wave - becomes important. Then effects of final-state interactions are evaluated in a unitarized scattering-length approach and found to be in the order of a 20% suppression close to threshold. Thus in present experiments at the Cooler Synchrotron COSY-J\"ulich for Q<=107 MeV the a_0^+ signal can reliably be separated from the non-resonant K^+\bar{K^0} background.Comment: 14 pages, 12 figures, submitted to EPJ

    a0(980)-f0(980) mixing and isospin violation in the reactions pN -> d a0, pd -> 3He/3H a0 and dd -> 4He a0

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    It is demonstrated that f_0-a_0 mixing can lead to a comparatively large isospin violation in the reactions pN -> da_0, pd -> ^3He/^3H a_0 and dd -> ^4He a_0 close to the corresponding production thresholds. The observation of such mixing effects is possible, e.g., by measuring the forward-backward asymmetry in the reaction pn -> d a_0^0 -> d eta pi^0.Comment: 14 pages, 5 figure

    Production of a0a_0-mesons in the reactions πNa0N\pi N \to a_0 N and ppda0+p p \to d a_0^+ at GeV energies

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    We investigate the reactions πNa0N\pi N \to a_0 N and ppda0+p p \to d a_0^+ near threshold and at medium energies. An effective Lagragian approach and the Regge pole model are applied to analyze different contributions to the cross section of the reaction πNa0N\pi N \to a_0 N. These results are used to calculate the differential and total cross sections of the reaction ppda0+p p \to d a_0^+ within the framework of the two-step model in which two nucleons produce an a0a_0-meson via π\pi -meson exchange and fuse to a deuteron. The necessity of new measurements on a0a_0 production and branching fractions (of its decay to the KKˉK\bar K and πη\pi\eta channels) is emphasized for clarifying the a0a_0 structure. Detailed predictions for the reaction ppda0+pp \to d a_0^+ are presented for the energy regime of the proton synchrotron COSY-J\"ulich.Comment: 9 pages, including 6 eps figure

    Medium effects in the production and pi0 gamma decay of omega-mesons in pA collisions in the GeV region

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    The omega-resonance production and its pi0 gamma decay in p-A reactions close to threshold is considered within the Intranuclear Cascade (INC) Model. The pi0 gamma invariant mass distribution shows two components which correspond to the omega decay 'inside' and 'outside' the nucleus, respectively. The 'inside' component is distorted by medium effects, which introduce a mass shift as well as collisional broadening for the omega-meson and its decaying pion. The relative contribution of the 'inside' component is analyzed in detail for different kinematical conditions and nuclear targets. It is demonstrated that a measurement of the correlation in azimuthal angle between the pi0 and gamma momenta allows to separate events related to the 'inside' omega decay from different sources of background when uncorrelated pi0's and gamma's are produced.Comment: 24 pages, 11 figure