Weak Interactions In Nuclei Research Articles

A formalism for weak interactions in nuclei

The neutrino-nucleus cross-section and the muon capture rate are discussed within a simple formalism which facilitates the nuclear structure calculations. The corresponding formulae only depend on four types of nuclear matrix elements, which are currently used in the nuclear beta decay. We have also considered the non-locality effects arising from the velocity-dependent terms in the hadronic current. We show that for both observables in 12C the higher order relativistic corrections are of the order of ~ 4% only, and therefore do not play a significant role.

Semileptonic weak interactions in nuclei within continuum RPA

Semileptonic weak reactions in nuclei at low and intermediate energies play an important role both in accelerator-based experiments in Neutrino Physics and in Neutrino Astrophysics. Theoretical estimates of such reaction rates are needed either to compare with the data or, in case they have not been measured, as input to astrophysical simulations. We show how weak observables can be calculated within Continuum RPA theory and present the most relevant applications.

Neutrino-astrophysics, nuclear physics, and particle physics at intense, pulsed, stopped-pion sources

Intense pulsed proton beams of ∼ 1 GeV impinging on high-Z targets are intense sources of νμ from the (τ=26 ns) decay of π +, and $$\bar \nu _\mu $$ and ν e from the stopped μ + decays. A pulse structure, narrow in time, allows the separation of reactions due to νμ from those from reactions involving $$\bar \nu _\mu$$ and νe. The energy spectra are in the energy range of interest to nuclear astrophysics. A number of possible experiments relevant to solar neutrinos, supernovae collapse, weak interactions in nuclei, and intrinsic properties of neutrinos are discussed.

Potential new neutrino physics at stopped-pion sources

Intense pulsed proton beams of ∼ 1GeV impinging on high - Z targets are intense sources of νμ from the (τ = 26 ns) decay of π +, and ν e and ν μ and ν e from the stopped ν + decays. A pulse structure, narrow in time, allows the separation of reactions due to ν μ from those from reactions involving ν μ and ν e . The energy spectra are in the energy range of interest to nuclear astrophysics. A number of possible experiments relevant to solar neutrinos, supernovae collapse, weak interactions in nuclei and intrinsic properties of neutrinos are discussed.

Measurement of the parity violating asymmetry Aγ in [formula omitted

The weak interaction between neutrons and protons has never been resolved experimentally. In analogy with the strong NN interaction, the weak NN interaction at low energy can be parametrized in terms of a meson exchange model with parity violating meson–nucleon couplings. Unlike the measured proton–proton weak interaction, the neutron–proton weak interaction is sensitive to the weak pion–nucleon coupling constant H π 1. This coupling, which is responsible for the longest-ranged part of the weak NN interaction and is therefore an essential part of any description of weak interactions in nuclei, remains undetermined despite many years of effort. A measurement of the gamma ray directional asymmetry A γ in the capture of polarized neutrons by parahydrogen has been proposed at Los Alamos National Laboratory. The goal of this experiment is to determine A γ with a relative standard uncertainty of <5×10 −9, which is smaller than all modern predictions for the size of the asymmetry. The design of the experiment is presented, with an emphasis on the techniques used for controlling systematic errors.

Nuclear Spin Responses for Neutrinos in Astroparticle Physics

Nuclear spin responses are of vital importance for studies of neutrinos, weakly interacting particles and of weak interactions in nuclei. The physics objectives are concerned with lepton nuclear physics within and beyond the standard theory. Here nuclei, which consist of elementary particles in good quantum (eigen) states, are used as excellent micro-laboratories for studying fundamental particles and interactions. Subjects discussed include neutrinos(ν) and weak interactions, weakly interacting massive particles as candidates for dark matters (DM), and other related problems. Experimental studies of them are made by investigating ultra rare nuclear processes at low background underground laboratories. Nuclear responses relevant to electroweak processes, neutrinos, and weakly interacting massive particles are discussed. Nuclear spin isospin responses associated with axial charged weak currents are investigated by using charge-exchange spin flip nuclear reactions at the RCNP ring cyclotron laboratory.

Nuclear and hypernuclear particle-hole states in the relativistic sigma - omega mean field theory: Nuclear matter formalism.

Studies of the closed core response to a perturbation in the Dirac Hamiltonian (due to an out-of-core baryon) are extended to particle-hole states in nuclear matter. Both isoscalar nucleon-particle--nucleon-hole states and \ensuremath{\Lambda}-particle--nucleon-hole hypernuclear states are considered. Core-response effects on the nuclear baryon current and the vector and scalar densities are studied, using both a perturbative treatment and linear response theory. While no essentially new physical insight is encountered by considering particle-hole states, there are many new and interesting applications. In particular, we mention applications to hypernuclei, meson-nucleus (especially ${\mathit{K}}^{+}$) interactions, meson photoproduction on nuclei, nuclear reactions, and nuclear transitions in inelastic scattering and weak interactions in nuclei. We point out interest in core-response effects related to nuclear transitions, where new physical insight is expected.

Inelastic neutrino scattering on 12C and 16O above the particle emission threshold

Recently a new formalism has been developed to described nuclear electromagnetic response within the continuum RPA theory. This model is extended in order to calculate cross sections for weak interactions in nuclei, in particular for inelastic neutrino scattering. The results of a numerical analysis are presented for 12C and 16O. We consider neutrino spectra like those generated in muon decay (relevant for terrestrial experiments) or in a supernova explosion. For the latter case we calculate neutral current cross sections for various neutrino-induced particle reactions on 12C and 16O, relevant for the ν-nucleosynthesis.

Weak Interactions in Nuclei

Recently a symbiotic relationship between particle and nuclear physics has developed, with techniques and ideas from one field fertilizing developments in the other. This work outlines concepts from modern particle physics important to the current understanding of nuclear physics and reviews experiments involving nuclei which have influenced the present particle physics view of the weak interaction. In his discussion, the author summarizes both past and present activity in the field and identifies areas for future work. Familiarity with quantum mechanics is assumed in the presentation of ideas in this book intended for readers at the graduate level and beyond. A major goal of Weak Interactions in Nuclei is to encourage further activity at the intersection of particle and nuclear physics, two path-breaking areas of study in modern physics. Originally published in 1989. The Princeton Legacy Library uses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These editions preserve the original texts of these important books while presenting them in durable paperback and hardcover editions. The goal of the Princeton Legacy Library is to vastly increase access to the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905.

Beta -decay anisotropies of the mirror nuclei 15O and 17F.

Measurements of the \ensuremath{\beta} anisotropy of the mirror nuclei $^{15}\mathrm{O}$ and $^{17}\mathrm{F}$, using on-line isotope separation and low-temperature nuclear orientation, are reported for the first time. Results of this novel approach are discussed in connection with the study of weak interactions in nuclei.

Lepton-induced weak interactions in nuclei in the 1 to 3 GeV range.

Differential cross sections are obtained for the reactions ${v}_{\ensuremath{\mu}}+^{12}\mathrm{C}\ensuremath{\rightarrow}^{12}\mathrm{N}+{\ensuremath{\mu}}^{\ensuremath{-}}$ and ${e}^{\ensuremath{-}}+^{12}\mathrm{C}\ensuremath{\rightarrow}^{12}\mathrm{B}+{v}_{e}$ for incoming lepton energies of 1 and 3 GeV. The contributions of individual form factors to the differential cross section are also found. A discussion of the utility of these processes for studying the weak nuclear current is given.

Semileptonic weak interactions in nuclei: A relativistic analysis

We use a consistent relativistic formalism, with relativistic Hartree wave functions and a covariant effective current operator with all the properties of the standard model, to study semileptonic weak processes in nuclei. Results are obtained for β-decay, μ- capture, charge-changing v-reactions and neutral v-scattering involving the isodoublet systems 17F 17O and 3H 3He.

Nuclear physics and quark/gluon QCD

In looking toward the future of Nuclear Physics I briefly discuss the questions of quark distributions in nuclei, weak interactions in nuclei, the applicability of QCD, and the question of seeing glue in nuclear matter.

Weak interactions in nuclei

Weak interactions in nuclei

Weak nuclear interactions in a hybrid baryon-quark model:p−pasymmetry

The hybrid multi-baryon-quark shell model of nuclei is developed for the study of weak interactions in nuclei. Application to the parity violating asymmetry in $p\ensuremath{-}p$ elastic scattering is carried out.NUCLEAR REACTIONS Weak asymmetry in elastic $\mathrm{pp}$ scattering. Energies up to 800 MeV. Quark model of weak interactions in nuclei. Quark structure of nuclei.

Pion field and weak interactions in nuclei

The subject of this session concerns the behaviour of the nucleons inside the nucleus; the question could be phrased in this way: to what extent is it useful to think of the nucleus as an assembly of protons and neutrons? Maybe you will be surprised by this question because one is so used to take this picture for granted; after all we can extract nucleons out of nuclei or we can form a nucleus by successive addition of nucleons. But this condition is not enough to justify this view. Let me give you an example: you can form cement by adding water to a powder of silicate. But certainly you will not recognise in a block of cement the water that is inside. The structure of the constituents has been changed to an extent that it makes it difficult to recognise what were the original constituents.

An experiment on isospin-changing parity violation involving hadrons in nuclei

An experiment is reported on the parity-violating reaction d(α, γ)6Li, leading to theJ P =0+,I=1,E x =3.562 MeV state, which, being a ΔI=1 transition, could be strongly enhanced by the presence of neutral currents in hadronic weak interactions in nuclei. The experiment has been carried out by exposing a deuterium target to a beam of α-particles reaching the resonant energy in the region in the middle of the tube containing the gas. Gamma-rays from this region are detected by a 90 cm3 Ge(Li) counter connected to a 4096 channel analyser through an amplifying and analysing chain. The various sources of the background of spurious counting in the Ge(Li) and the procedure adopted to reduce their effect are discussed. We find no evidence for a nonzero parity-violating width of the 3.562 MeV state of6Li and can set an upper limit for this width of 8·10−4 eV, which is an order of magnitude or more lower than that obtained in the previous experiments on this reaction.

Weak interactions in nuclei

We would like to close these brief notes on the role played by symmetries in weak nuclear processes with the following conclusions:

Semi-leptonic weak and electromagnetic interactions in nuclei with application to 16O

Electron scattering is shown to provide a basis for analyzing semi-leptonic weak interactions in nuclei essentially independent of detailed models of nuclear wave functions. Application is made to 16O. One result is the identification of a second-class-current detector.