21,900 research outputs found

    Structure of heavy baryons in a pion mean-field approach

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    In this talk, we briefly review a series of recent works on singly heavy baryons, based on a pion mean-field approach. In the limit of the infinitely heavy quark mass, heavy baryons are governed mainly by the light degress of freedom. Taking the number of colors to be infinity, a heavy baryon arises as a state consisting of Ncβˆ’1N_c-1 valence quarks bound by the pion mean fields created self-consistently. Within this framework, we present the results of the mass spectra of the charmed and bottom baryons, and their magnetic moments. The behavior of the electromagnetic form factors will be also mentioned.Comment: 4 pages, No figure. Contribution to the proceedings of "8th International Conference on Quarks and Nuclear Physics (QNP2018)", November 13-17, 2018, Tsukuba, Japa

    Remark on the Limit Case of Positive Mass Theorem for Manifolds with Inner Boundary

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    In [5] Herzlich proved a new positive mass theorem for Riemannian 3-manifolds (N,g)(N, g) whose mean curvature of the boundary allows some positivity. In this paper we study what happens to the limit case of the theorem when, at a point of the boundary, the smallest positive eigenvalue of the Dirac operator of the boundary is strictly larger than one-half of the mean curvature (in this case the mass m(g)m(g) must be strictly positive). We prove that the mass is bounded from below by a positive constant c(g),m(g)β‰₯c(g)c(g), m(g) \geq c(g), and the equality m(g)=c(g)m(g) = c(g) holds only if, outside a compact set, (N,g)(N, g) is conformally flat and the scalar curvature vanishes. The constant c(g)c(g) is uniquely determined by the metric gg via a Dirac-harmonic spinor.Comment: 12 pages, latex2

    K0Ξ›K^0\Lambda Photoproduction with Nucleon Resonances

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    We investigate the reaction mechanism of K0Ξ›K^0 \Lambda photoproduction off the neutron target, i.e., Ξ³nβ†’K0Ξ›\gamma n \to K^0 \Lambda, in the range of Wβ‰ˆ1.6βˆ’2.2W\approx 1.6-2.2 GeV. We employ an effective Lagrangian method at the tree-level Born approximation combining with a Regge approach. As a background, the Kβˆ—K^*-Reggeon trajectory is taken into account in the tt channel and Ξ›\Lambda and Ξ£\Sigma hyperons in the uu-channel Feynman diagram. In addition, the role of various nucleon resonances listed in the Particle Data Group (PDG) is carefully scrutinized in the ss channel where the resonance parameters are extracted from the experimental data and constituent quark model. We present our numerical results of the total and differential cross sections and compare them with the recent CLAS data. The effect of the narrow nucleon resonance N(1685,1/2+)N(1685,1/2^+) on cross sections is studied in detail and it turns out that its existence is essential in K0Ξ›K^0 \Lambda photoproduction to reproduce the CLAS data.Comment: 4 pages, 3 figures, Proceedings of "8th International Conference on Quarks and Nuclear Physics (QNP2018)", November 13-17, 2018, Tsukuba, Japa
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