Abstract: We present here a microscopic nuclear-structure calculation of a beta-electron spectrum including all the beta-decay branches of a high Q-value reactor fission product contributing significantly to the reactor antineutrino energy spectrum. We perform large-scale nuclear shell-model calculations of the total electron spectrum for the beta(-) decay of Rb-92 to states in Sr-92 using a computer cluster. We exploit the beta-branching data of a recent total absorption gamma-ray spectroscopy (TAGS) measurement to determine the effective values of the weak axial-vector coupling, g(A), and the weak axial charge, g(A)(gamma(5)). By using the TAGS data we avoid the bias stemming from the pandemonium effect which is a systematic error biasing the usual beta-decay measurements. We take fully into account all the involved allowed and forbidden beta transitions, in particular the first-forbidden nonunique ones which have earlier been shown to be relevant in the context of the reactor-antineutrino flux anomaly and the unexplained spectral shoulder, the “bump,” the former one having been interpreted as one of the strongest evidence for the existence of sterile neutrinos. Here we are able to present quantitative evidence for the relevance of forbidden nonunique beta(-) decays in a total beta spectrum of a fission product, in this case( 92)Rb, which is one of the major contributors to the total reactor antineutrino spectral shape. We demonstrate that taking the forbidden spectral shapes fully into consideration leads for Rb-92 to a 2.6%-4.6% reduction in the expected inverse beta-decay rate at the reactor antineutrino telescopes. We also confirm by our calculation of a total beta-electron spectrum that the forbidden transitions can contribute to the formation of the spectral bump in the reactor-antineutrino flux profile.

Abstract: The total and differential cross sections for associated strangeness production in the pp -> pK(+) K(-)p and pp -> pK(+)pi(0)Sigma(0) reactions have been studied in a unified approach using an effective Lagrangian model. It is assumed that both the K(-)p and pi(0)Sigma(0) final states originate from the decay of the Lambda(1405) that was formed in the production chain pp -> p(N*(1535). K+ Lambda(1405)). The available experimental data are well reproduced, especially the ratio of the two total cross sections, which is much less sensitive to the particular model of the entrance channel. The significant coupling of the N*(1535) to Lambda(1405)K is further evidence for large ss components in the quark wave function of the N*(1535).

Abstract: The cross section of the reaction Au-197(n,gamma) was measured with the time-of-flight technique at the n_TOF (neutron time-of-flight) facility in the unresolved resonance region between 5 and 400 keV using a pair of C6D6 (where D denotes H-2) liquid scintillators for the detection of prompt capture gamma rays. The results with a total uncertainty of 3.9%-6.7% for a resolution of 20 bins per energy decade show fair agreement with the Evaluated Nuclear Data File Version B-VII.0 (ENDF/B-VII.0), which contains the standard evaluation. The Maxwellian-averaged cross section (MACS) at 30 keV is in excellent agreement with the one according to the ENDF/B-VII.0 evaluation and 4.7% higher than the MACS measured independently by activation technique. Structures in the cross section, which had also been reported earlier, have been interpreted as being due to clusters of resonances.