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21世紀COEセミナー「UA(1) symmetry and nucleon parity doubling」

日時 平成19年(2007年)2月2日(金)16:00〜
場所 核物理研究センター4階 Lecture room
講師 Veljko Dmotrasinovic (Vinca Institute, Serbia)
題目 UA(1) symmetry and nucleon parity doubling
概要 We examine the role of UA(1) symmetry and its breaking in a quartet of the nucleon, Roper and their odd parity resonances. Firstly we show that the UA(1) transformations connect two independent interpolating fields in the form of quark trilinears. They form two irreducible representations of UA(1) symmetry, one “mirror” and another “naive”, the latter with triple axial baryon charge. We also examine their SUL(2)×SUR(2) transformations of these fields and show that for each local nucleon field there is one with a derivative in the “mirror” representation. Thence we construct the most general non-derivative effective intearction consisting of these four nucleon fields in the good UA(1) and SU(2)L×SU(2)R symmetry limit. After spontaneous breaking down to SU(2)V, we show that the mass splittings induced by this effective interaction can reproduce all masses of the four nucleon states, if physical states are suitably identified. We try and use the experimental nucleon resonance decay data to fix other free parameters.

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