We present high resolution UV-photoelectron spectra of cold mass selected Cun-, Agn-, and Aun- with n=53-58. The observed electron density of states is not the expected simple electron shell structure, but is strongly influenced by electron-lattice interactions. Only Cu55- and Ag55- exhibit highly degenerate states. This is a direct consequence of their icosahedral symmetry, as is confirmed by density functional theory calculations. Neighboring sizes exhibit perturbed electronic structures, as they are formed by removal or addition of atoms to the icosahedron and therefore have lower symmetries. Gold clusters in the same size range show completely different spectra with almost no degeneracy, which indicates that they have structures of much lower symmetry. This behavior is related to strong relativistic bonding effects in gold, as demonstrated by ab initio calculations for Au55-.

We report on a new measurement of neutron beta-decay asymmetry. From the result A(0) = -0.1189(7), we derive the ratio of the axial vector to the vector coupling constant lambda = g(A)/g(V) = -1.2739(19). When included in the world average for the neutron lifetime tau = 885.7(7) s, this gives the first element of the Cabibbo-Kobayashi-Maskawa (CKM) matrix V(ud). With this value and the Particle Data Group values for V(us) and V(ub), we find a deviation from the unitarity condition for the first row of the CKM matrix of Delta = 0.0083(28), which is 3.0 times the stated error.

A dynamical model for S-and P-wave correlated 2π (and KK) exchange between a kaon and a nucleon is presented, starting from corresponding NN → KK amplitudes in the pseudophysical region, which have been constructed from nucleon, ∆-isobar and hyperon (Λ, Σ) exchange Born terms and a realistic meson exchange model of the ππ → KK and KK → KK amplitude. The contribution in the s-channel is then obtained by performing a dispersion relation over the unitarity cut. In the ρ-channel, considerable ambiguities exist, depending on how the dispersion integral is performed. Our model, supplemented by short range interaction terms, is able to describe empirical K + N data below pion production threshold in a satisfactory way.

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