https://authors.library.caltech.edu/39827/7/1303.2371v1.pdf

Electric Dipole Moments of Nucleons, Nuclei, and Atoms: The Standard Model and Beyond

Precision Tau Physics

The last decades brought impressive progress in synthesizing and studying properties of nuclides located very far from the beta stability line. Among the most fundamental properties of such exotic nuclides, the ones usually established first are the half-life, possible radioactive decay modes, and their relative probabilities. When approaching limits of nuclear stability, new decay modes set in. First, beta decays are accompanied by emission of nucleons from highly excited states of daughter nuclei. Second, when the nucleon separation energy becomes negative, nucleons start being emitted from the ground state. A review of the decay modes occurring close to the limits of stability is presented. The experimental methods used to produce, identify, and detect new species and their radiation are discussed. The current theoretical understanding of these decay processes is reviewed. The theoretical description of the most recently discovered and most complex radioactive process---the two-proton radioactivity---is discussed in more detail.

Radioactive decays at limits of nuclear stability

Hidden pseudospin and spin symmetries and their origins in atomic nuclei

Experiments with cold and ultracold neutrons have reached a level of precision such that problems far beyond the scale of the present standard model of particle physics become accessible to experimental investigation. Because of the close links between particle physics and cosmology, these studies also permit a deep look into the very first instances of our Universe. First addressed in this article, in both theory and experiment, is the problem of baryogenesis, the mechanism behind the evident dominance of matter over antimatter in the Universe. The question of how baryogenesis could have happened is open to experimental tests, and it turns out that this problem can be curbed by the very stringent limits on an electric dipole moment of the neutron, a quantity that also has deep implications for particle physics. Then the recent spectacular observation of neutron quantization in the Earth's gravitational field and of resonance transitions between such gravitational energy states is discussed. These measurements, together with new evaluations of neutron scattering data, set new constraints on deviations from Newton's gravitational law at the picometer scale. Such deviations are predicted in modern theories with extra dimensions that propose unification of the Planck scale with the scale of themore » standard model. These experiments start closing the remaining ''axion window'' on new spin-dependent forces in the submillimeter range. Another main topic is the weak-interaction parameters in various fields of physics and astrophysics that must all be derived from measured neutron-decay data. Up until now, about 10 different neutron-decay observables have been measured, much more than needed in the electroweak standard model. This allows various precise tests for new physics beyond the standard model, competing with or surpassing similar tests at high energy. The review ends with a discussion of neutron and nuclear data required in the synthesis of the elements during the ''first three minutes'' and later on in stellar nucleosynthesis.« less

The neutron and its role in cosmology and particle physics

The determination of the Cabibbo–Kobayashi–Maskawa (CKM) matrix element Vud is reviewed. Data from 0+ → 0+ superallowed beta decay in nuclei, neutron decay, beta decay of odd-mass mirror nuclei and pion beta decay are considered. Theoretical radiative and isospin-symmetry breaking corrections are applied. The most precise result comes from the nuclear 0+ → 0+ decays, which yield a recommended value of |Vud| = 0.974 25(22). We further summarize the data leading to the CKM matrix element Vus: Kl3 decays, Kl2 decays, hyperon decays and hadronic tau decay. Again SU(3)-symmetry breaking corrections (from lattice QCD) and radiative corrections are applied. We adopt values from Kl3 decay of |Vus| = 0.2246(12) and from Kl2 decay of |Vus/Vud| = 0.2319(14). From the three data just cited, a least squares fit determines two CKM matrix elements: |Vud| = 0.974 25(22) and |Vus| = 0.225 21(94). Data leading to the third member of the top row of the CKM matrix, Vub, are summarized as well but, being of order 10−3, that matrix element contributes negligibly to the unitarity sum, |Vud|2 + |Vus|2 + |Vub|2. We find this sum to be 0.999 90(60) showing unitarity to be satisfied to a precision of 0.06%. We discuss the constraints this result places on selected extensions to the standard model.

J C Hardy

Papers

The evaluation of V(ud) and its impact on the unitarity of the Cabibbo-Kobayashi-Maskawa quark-mixing matrix