Current Weak Interactions Research Articles

Nuclear Neutrino Spectra in Late Stellar Evolution

Neutrinos are the principle carriers of energy in massive stars, beginning from core carbon burning and continuing through core collapse and after the core bounce. In fact, it may be possible to detect neutrinos from nearby pre-supernova stars. Therefore, it is of great interest to understand the neutrino energy spectra from these stars. Leading up to core collapse, beginning around core silicon burning, nuclei become dominant producers of neutrinos, particularly at high neutrino energy, so a systematic study of nuclear neutrino spectra is desirable. We have done such a study, and we present our sd-shell model calculations of nuclear neutrino energy spectra for nuclei in the mass number range A = 21 – 35. Our study includes neutrinos produced by charged lepton capture, charged lepton emission, and neutral current nuclear deexcitation. Previous authors have tabulated the rates of charged current nuclear weak interactions in astrophysical conditions, but the present work expands on this not only by providing neutrino energy spectra, but also by including the heretofore untabulated neutral current de-excitation neutrino pairs.

Weak currents in nondiagonal leptonic processes

Nondiagonal leptonic processes are studied on the basis of neutral (NC) and charged (CC) weak current interactions. NC and CC descriptions of recoil electron spectra upon the elastic scattering of neutral (anti)leptons, including arbitrary vector and axial-vector current constants that can be real and complex or purely imaginary, are presented. Based on the NC description, the spectrum of muons originating upon the inelastic scattering of a muonic neutrino by a polarized target electron, the total cross section of this process and neutron conversion of an electron–muon pair, as well as the charged and neutral components of the electron spectrum emitted in muon decay are obtained. The possibility of forbidden nondiagonal neutral electron–muon currents emerging in these processes is analyzed.

Firstβ−νcorrelation measurement from the recoil-energy spectrum of Penning trappedAr35ions

We demonstrate a novel method to search for physics beyond the standard model by determining the $\ensuremath{\beta}\ensuremath{-}\ensuremath{\nu}$ angular correlation from the recoil-ion energy distribution after $\ensuremath{\beta}$ decay of ions stored in a Penning trap. This recoil-ion energy distribution is measured with a retardation spectrometer. The unique combination of the spectrometer with a Penning trap provides a number of advantages, e.g., a high recoil-ion count rate and low sensitivity to the initial position and velocity distribution of the ions and completely different sources of systematic errors compared to other state-of-the-art experiments. Results of a first measurement with the isotope $^{35}\mathrm{Ar}$ are presented. Although currently at limited precision, we show that a statistical precision of about 0.5% is achievable with this unique method, thereby opening up the possibility of contributing to state-of-the-art searches for exotic currents in weak interactions.

The Turbulence Characteristics of Radar Backscatter Coefficient Caused by Wave and Weak Current Interaction on Ocean Surface

Based on radar backscattering turbulence model of ocean surface caused by wave-current interaction,For weak ocean current,it simplifies the model and calculates the radar backscattering coefficient's turbulence caused by weak ocean current.It analyzes the relationships between the results and current field,current amplitude,wind speed,wave-current angle,radar wave band and radar incidence angle.Then it gives the turbulence characteristics.Thus this paper will provide valuable help for studying the detecting capability of radar for ocean surface current.

SOLAR NEUTRINOS AND THE JUPITER

Judging from the fact that the planet Jupiter is bigger in size than the Earth by 103 while is smaller than the Sun by 103, the solar neutrinos, when encounter the Jupiter, may have some visible effects. We estimate how much energy/power carried by solar neutrinos get transferred by this unique process. Solar neutrinos, despite of their feeble neutral weak current interactions, might deposit enough energy in the Jupiter.

Axial-vector current in nuclear many-body physics

Weak-interaction currents are studied in a recently proposed effective field theory of the nuclear many-body problem. The Lorentz-invariant effective field theory contains nucleons, pions, isoscalar scalar ($\sigma$) and vector ($\omega$) fields, and isovector vector ($\rho$) fields. The theory exhibits a nonlinear realization of $SU(2)_L \times SU(2)_R$ chiral symmetry and has three desirable features: it uses the same degrees of freedom to describe the axial-vector current and the strong-interaction dynamics, it satisfies the symmetries of the underlying theory of quantum chromodynamics, and its parameters can be calibrated using strong-interaction phenomena, like hadron scattering or the empirical properties of finite nuclei. Moreover, it has recently been verified that for normal nuclear systems, it is possible to systematically expand the effective lagrangian in powers of the meson fields (and their derivatives) and to reliably truncate the expansion after the first few orders. Here it is shown that the expressions for the axial-vector current, evaluated through the first few orders in the field expansion, satisfy both PCAC and the Goldberger--Treiman relation, and it is verified that the corresponding vector and axial-vector charges satisfy the familiar chiral charge algebra. Explicit results are derived for the Lorentz-covariant, axial-vector, two-nucleon amplitudes, from which axial-vector meson-exchange currents can be deduced.

Chirality and the weak current interactions in molecular spectroscopy: a symmetry analysis

The influence of the parity violating weak current interactions between nucleons and electrons is discussed with reference to molecular spectroscopy and the enantiomeric energy inequivalence. Several novel effects are suggested, based on simple symmetry arguments applied to isolated molecules and ensembles. By measuring these effects spectroscopically, in the laboratory and in the spectra of distant galactic matter receding near the velocity of light, avenues may be found which lead to a new appreciation of the role of the W boson mediator in molecular spectroscopy and dynamics.

Sub-leading logarithmic mass-dependence in heavy-meson form-factors

We calculate the two-loop anomalous dimension and the first-order coefficient function of weak-interaction currents in the heavy-quark effective field theory. Together with the two-loop QCD β-function, these quantities form the complete sub-leading logarithmic corrections to the mass-factorization of weak form factors.

On the observability of parity and time reversal violating interactions by trapped ion spectroscopy

The feasibility to measure neutral weak current interactions by spectroscopy on trapped ions is investigated. The sensitivity of the proposed experiment is compared to the sensitivity of similar experiments using atomic gases or beams. It is shown that there is no advantage as far as that part of the interaction is concerned which is a vector in the nucleon current and an axial vector in the electron current. This is mainly due to the relatively low ion density. The circular polarization however depending upon the nuclear spin orientation appears to be proportional to the coherence time, which is three orders of magnitude longer than in ordinary atomic beam resonance experiments. It is pointed out that the same method can be used to measure possible nuclear electric dipole moments.

Beta-ray branching in the decay ofF20

Measurements on the $\ensuremath{\gamma}$-ray spectrum from 11-sec $^{20}\mathrm{F}$ resulted in an energy of 3332.51(19) keV for the cascade $\ensuremath{\gamma}$ ray from the $^{20}\mathrm{Ne}$ 4.97-MeV state and a $\ensuremath{\beta}$-branching intensity to this level of 0.90(4) \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}4}$ per decay. The corresponding $log{f}_{0}t$ value is 7.16(2), and the excitation energy of the $^{20}\mathrm{Ne}$ state is 4966.51(20) keV.[RADIOACTIVITY $^{20}\mathrm{F}$; measured ${E}_{\ensuremath{\gamma}}$, ${I}_{\ensuremath{\gamma}}$; Ge(Li) detector; deduced ${E}_{x}$, $\ensuremath{\beta}$ branching, and $log{f}_{0}t$ value.]

Second-Class Currents in Weak Interactions

Second-Class Currents in Weak Interactions

Second-Class Currents in Weak Interactions

Second-Class Currents in Weak Interactions

Social currents in weak interactions

At the end of his concluding remarks, summarizing the reports at the 1962 International Conference on High Energy Physics at CERN, Victor Weisskopf referred to the excitement caused by experimental claims that the selection rule known as the ΔS = ΔQ rule did not hold and showed the New Yorker cartoon reprinted opposite.

Flavor-changing neutral-current processes in gauge models and strong interactions

The effect of strong interactions on flavor-changing neutral-current (FCNC) processes is discussed. In order that the FCNC semileptonic process I ..-->.. F + ..nu.. + nu-bar does not take place to order G/sub F/ nor to order G/sub F/..cap alpha.., the hadronic matrix elements of weak-interaction currents must satisfy (A) approx.O (k/sup -2/) O/sup F I//sub munu/as k = (k/sup 2/ + (ik/sub 0/)/sup 2/)/sup 1/2/ ..-->.. infinity, where I and F are hadronic states of different flavors and J/sup 0//sub ..mu../and J/sup + -/..mu.. are neutral and charged weak-interaction currents, respectively, while O/sup F I//sub munu/stands for the matrix elements of finite operators. By examining conditions (A) and (B), we show that if the FCNC quark process q/sup I/ ..-->.. q/sup F/ + ..nu.. + nu-bar is suppressed to order G/sub F/ and to order G/sub F/..cap alpha.., the semileptonic process I ..-->.. F + ..nu.. + nu-bar is also suppressed to the same order, where the q/sup I//sup( F)/ quark carries the same flavor as the hadronic state I (F).

Weak interactions in deuterons: Exchange currents and nucleon-nucleon interaction

While the meson-exchange electromagnetic current has been tested with an impressive success in the two-nucleon system, nothing much is known about the reliability of the exchange currents in weak interactions. We study this question using muon absorption in the deuteron, μ − + d → n + n + ν. The meson-exchange current, previously derived in parallel to those of the electromagnetic interaction, is checked for consistency against the p-wave piece of the p + p → d + π + process near threshold and then tested with the total capture rate for which some (though not so accurate) data are available. We then use the same Hamiltonian to calculate the matrix elements for the solar neutrino processes p + p → d + e + ν and p + p + e − → d + ν in the hope that they would be measured and help resolve the solar neutrino puzzle. Finally we make a detailed analysis of the differential capture rate d Γ/d E n, E n being the kinetic energy in the c.m. of the two neutrons, in the expectation that it will be used to pin down the ever elusive n-n scattering length.

Neutral currents in weak interactions and molecular asymmetry.

Weak interactions are parity violating forces, i.e. they differentiate between mirror images. Therefore it is a very attractive hypothesis to invoke weak interactions in explaining the origin of molecular asymmetry. It is, however, not clear whether weak interactions may operate between electrons and/or between electrons and protons? For these types of interactions so called neutral currents are needed. Recent experiments with muon neutrinos at CERN gave some evidence for the existence of neutral currents. Thus we may suppose that parity violating forces are active in molecules. In the first part of this paper a very elementary theory of weak interactions is outlined with special reference to the discovery of neutral currents. In the second part we show how weak interactions may differentiate between mirror image molecules. The asymmetrically distributed static charges in chiral molecules represent a helical potential field. This potential field may exert an effect on the orbital electrons and therefore coupling of spins and momenta occurs. Thus the enantiomers are parity transformed images not only as geometrical bodies, but their orbital electrons are parity transformed too as "a helical electron gas". Weak interactions will differentiate between L and D forms because their orbital electrons have a nonzero spin polarization with respect to their velocity.

Muonless neutrino-interaction events and the weak currents

The baryon-current model of Sakurai for understanding neutral currents in weak interactions is extended to include $\ensuremath{\Delta}I=1$ contribution and/or axial-vector terms in $V\ensuremath{-}A$ form with the experimental implications spelled out.

Comments on Parity Violating Neutral Currents in Weak Interactions

The possibility of detecting weak neutral currents and the parity violating effect in e/sup +/e/sup -/ yields mu /sup +/ mu /sup -/, e/sup +/e/ sup -/ yields SIGMA SIGMA ( LAMBDA LAMBDA ) e/sup +/e/sup -/ yields pi / sup +/ pi /sup -/, and e/sup +/e/sup -/ yields pX ( LAMBDA X, SIGMA /sup +/X) colliding-beam interactions is discu ssed. It is concluded that, at prcscnt, the practical possibility is limited to the pure leptonic processes. ( Ll3S)

Mirror asymmetry, meson exchanges and second class currents

We explore the consequences on nuclear beta decay of the possible existence of second-class axial currents in weak interaction. It is found that due to off-mass- shell and meson-exchange complications, the beta-decay rates - for instance, the mirror asymmetries - cannot yield unambiguous information on the second- class coupling, unless one has some knowledge of the divergence of the current. If we assume that the divergence vanishes, then the off-shell ambiguity can be eliminated through a low-energy theorem and the meson-exchange corrections uniquely determined so that the mirror asymmetries can yield direct information on the fundamental second-class coupling. As a result of the divergence-equals- zero hypothesis, the meson-exchange effect which is essential for the elimination of the ambiguity turns out to have the same energy dependence as the impulse contribution. We also obtain an interesting relation connecting the coupling constant for the semi-leptonic decay of ω into a soft pion to the pion exchange contribution to the mirror asymmetry. Finally we review a few experiments which have a direct bearing on the existence or non-existence of the second-class axial coupling free of the off-shell and meson-exchange complications, and which can eventually support or rule out our hypothesis.

Photon Low-Energy Theorem and the Radiative Decays of theΩ−Particle

The photon low-energy theorem due to Low, and to Adler and Dothan is applied to the two-body radiative decays of the ${\ensuremath{\Omega}}^{\ensuremath{-}}$ particle. The decay amplitudes are evaluated in the resulting pole model. With the usual assumptions of octet dominance and $\mathrm{CP}$ invariance for the weak Hamiltonian, it is shown that the parity-violating amplitude for ${\ensuremath{\Omega}}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\Xi}}^{*\ensuremath{-}}\ensuremath{\gamma}$ should be zero for a current $\ifmmode\times\else\texttimes\fi{}$ current weak interaction. The weak vertex parameters obtained from a fit to the experimental data on the nonleptonic decays of the hyperons are used to estimate the decay amplitudes and the decay rates. The implications of the results obtained earlier by Raszillier and Burlacu on the three-body radiative decays ${\ensuremath{\Omega}}^{\ensuremath{-}}\ensuremath{\rightarrow}{B}_{8}+P+\ensuremath{\gamma}$ are discussed. Theoretical estimates for the decay rates of weak decay modes of the ${\ensuremath{\Omega}}^{\ensuremath{-}}$ particle have been compiled.