Parity-nonconservation effects in the photodisintegration of polarized deuterons

P-odd correlations in deuteron photodisintegration are considered. It is shown that, in the case of unpolarized deuterons, π-meson exchanges do not contribute to these correlations. For polarized deuterons, the contribution of π-meson exchanges to the P-odd correlation is about 0.3×10^?8. The contribution to P-odd effects from weak interactions at short distances substantially exceeds the contribution from π-meson exchanges.     

Compton polarimetry detection of small circularly and linearly polarized impurities in Mössbauer 8.4 keV (3/2-1/2) M1 γ-transition of 169Tm

The arrangement of an experiment to detect the P?odd and P, T?odd polarized part of the Mössbauer (⁺3/2– ⁺1/2) gamma transition of a deformed ¹⁶⁹Tm nucleus with an energy of 8.4 keV by Compton polarimetry is discussed. Tm ₂O₃ single crystal with a quadrupolarly split Mössbauer spectrum is proposed as a resonance polarizer. A Be-scatterer-based Compton polarimeter and a synchronously detecting system will be used to measure the P-odd circular polarization P_Cand P, T-odd linear polarization P_L.The expected accuracy of measuring the relative magnitude of the P, T-odd contribution is about 1% of the magnitude of usual weak nucleon–nucleon interaction.     

Search for P-ODD asymmetry in the radiative cross-section of the interaction of neutrons with lead nuclei

The P-odd effect in the radiation cross section of capture of longitudinally polarized neutrons in a sample of natural lead is measured. The experiment was performed at PF1B facility at the Institut Max von Laue-Paul Langevin. The neutron polarization P _n was 92%, the total flux of polarized neutrons was ～3 × 10¹⁰ n/s, and the mean neutron wavelength was λ = 4.7 Å. Taking into account “0-test” we estimated the asymmetry: a _γ(^natPb) = (2.3 ± 3.5) × 10^?7, i.e., α _γ ≤ 8.1 × 10^?7 at 90% confidence level.     

Schiff moment of the mercury nucleus and the proton dipole moment

The Schiff moment of the ¹⁹⁹Hg nucleus is calculated using finite range P-and T-violating weak nucleon-nucleon interaction. Both the contributions of the P-and T-odd interaction and of internal nucleon electric dipole moments to the Schiff moment of ¹⁹⁹Hg are calculated. The contribution of the proton electric dipole moment is obtained via core-polarization effects treated in the framework of RPA with effective residual interactions. We derive a new upper bound |d _p |<5.4×10^?24e cm for the proton electric dipole moment.     

Parity violating effects in dilepton production using polarized targets

Parity violating effects in PP → μ⁺μ^?X and $\text{P}\text{P}\text{→ μ}{}^{\mathrm{+}}\text{μ}{}^{\mathrm{?}}\text{X}$ with the polarized targets have been calculated in the parton picture. The weak neutral currents used are based on an SU(2)_L × SU(2)_R × U(1) model. The result for the Weinbergy-Salam model occurs as a special case.     

Electromagnetic and weak interactions in stochastic space-time: A review

A scheme for a nonlocal theory of quantized fields based on the hypothesis of stochastic space is proposed. Within this scheme the gauge-invariant quantum electrodynamics of particles with spin 0, 1/2, 1 and four-fermion weak interactions are constructed, and nonlocal corrections to the anomalous magnetic moments of leptons and to the Lamb shift are calculated. Some consequences of the neutrino oscillations and the electromagnetic properties of neutrinos are considered in detail. Further the rare decayK _L ⁰ →Μ⁺Μ^? and the mass difference ofK _L ⁰ andK _S ⁰ mesons are investigated in this model. It is shown that the parameter of nonlocality (elementary lengthl) of weak interactions which can characterize a domain of unification of weak and electromagnetic interactions is ～10^?16 cm. The low-energy experiments imply that quantum electrodynamics is valid up to distances of order ～10^?15 cm.     

Discovery of a <Emphasis Type="Italic">P</Emphasis>-odd effect in triton emission from the reaction <Superscript>6</Superscript>Li(<Emphasis Type="Italic">n</Emphasis>, α)<Superscript>3</Superscript>H

The results of measuring the P-odd asymmetry (S_n · P_t) for triton emission from the reaction ⁶Li(n, α)³H are presented. Here, S_n is the neutron spin and P_t is the triton momentum. Three series of measurements were performed, one at the Petersburg Nuclear Physics Institute (Gatchina, Russia) in a vertical neutron beam from the PWR reactor and two in the PF1B beam from the reactor at the Institute Laue-Langevin (Grenoble, France). On the basis of all three experiments, the P-odd asymmetry coefficient was found to be α_PN = ?(8.6 ± 2.0) × 10^?8. The results of zero experiments and calculations give every reason to believe that the above P-odd asymmetry is due to the reaction being studied.     

New results on deep inelastic processes from generalized vector dominance

A formulation of generalized vector dominance (GVD), consistent with the parton model (PM) for deep inelastic electroproduction, is presented. The parton distributions at small x are correctly predicted in terms of the photoabsorption parameters. It is found that no charmed partons exist in the sea of the nucleon. The pomeron ??_c coupling and the ?_c ? photoproduction cross section are negligible. The ratio σ_L/σ_T for deep inelatic and diffractive electroproduction is found to be small. This is related to the prediction that the highest Regge singularity coupled to longitudinal vector mesons is a cut with intercept minus one. In the time-like region it implies that the angular distribution in e⁺e^?→ π + X is ～ (3?cos²Θ), in consistence with experiment and disagreement with PM. Finally the large value of σ(e⁺e^? → hadrons) is attributed to a series of ?_c's.     

Search for <Emphasis Type="Italic">P</Emphasis>-odd asymmetry of prompt neutron emission in <Superscript>235</Superscript>U fission induced by cold polarized neutrons

The preliminary result of the P-odd asymmetry of prompt neutron emission in ²³⁵U fission induced by polarized cold neutrons is a=(2.7±0.8)×10^?5. Only scission neutrons can show such asymmetry, whereas neutrons emitted by excited fragments are the unavoidable background, which suppress the sought asymmetry. The P-odd asymmetry of light fragment emission for ²³⁵U is equal to (8.4±0.6)×10^?5. Assuming that the last figure defines the parity mixture of the fissile nucleus, then the suppression factor is equal approximately to 3.     

Parity nonconservation in the circular polarization of primary photons of the radiation accompanying electron conversion in the 5/2− → 5/2+ nuclear transition in the 229Pa91 nucleus

The ground state of ²²⁹Pa₉₁ is a 5/2^± doublet, with the splitting energy being 220+-50 eV. A direct observation of P-odd effects in this system is of great interest, since this may furnish information about the parity-nonconserving effective one-nucleon potential. Since a transition between two oppositeparity doublet states is accompanied by a strong conversion, it is possible to study P-odd mixing by exploring the conversion-electron helicity and the circular polarization P _γ of the lines of atomic radiation that arises upon the filling of a hole in the 6s _1/2, 6p _1/2, and 6p _3/2 shells of the ²²⁹Pa₉₁ atom. Since P _γ is about 3–5% for individual atomic transitions, experiments aimed at observing parity-nonconservation effects on this basis are feasible.     

CP violation andZ boson decays

We present a general discussion ofCP-violating effects in the following two and three body decays of theZ boson:Z→l ⁺ l ^?,Z→l ⁺ l ^?γ, wherel=e, μ, τ andZ→2 jets,Z→ 2 jets+γ, andZ→ 3 jets. Experimental observables sensitive toCP violation in these decays are discussed systematically for the case that polarizations of final state particles are not observed. It is shown that the standard model predicts only extremely smallCP-violating effects for the above decays. PossibleCP-violating interactions beyond the standard model are parametrized in terms of aCP-odd effective Lagrangian containing coupling constants proportional to Λ _P ^-1 and Λ _P ^-2 . Here Λ _CP is the mass scale associated with the assumed new interactions. We give estimates of the bounds obtainable for Λ _CP in experiments at LEP1.     

Triple correlation in the 10B(n, αγ)7Li reaction

The formally T-odd triple correlation between the directions of the momenta of α particle and γ quantum and the polarization pseudovector of a thermal neutron was examined for the ¹⁰B+n=⁷Li+⁴He+γ reaction. Such T-odd correlations can be directly used for checking time reversal invariance in the elastic scattering of particles. In more complex reactions, this correlation can occur as a result of particle interactions in the entrance and exit channels of the reaction and, being a background effect, requires correct theoretical or direct experimental estimation. Our experiments gave an upper limit of 3.2×10^?4 (90% confidence level) for the possible T-odd asymmetry parameter in the reaction under study.     

P-odd one-meson exchanges revisited: a non-linear chiral model approach

Coupling constants of theP-odd interaction of nucleon with the π-, ρ-, ω-mesons are calculated in the non-linear chiral model. The hierarchy of these constants governed by small parameters sin² θ _w and 1/N _c is established. According to this hierarchy the ratio of the weak πNN and ρNN coupling constants is small, being ?sin² θ _w /N _c . The absolute values of all considered constants prove to be essentially larger than those in theSU(6) _W model, thus pointing that theP-odd effects due to the overlap of the nucleons' wave functions are of importance.     

Simple tests of quark-nucleon reciprocity

The inclusive cross-section for the production of a single hadron in deep inelastic electroproduction is studied in a dual resonance model. The Bjorken scaling behaviour in the virtual photon fragmentation region for finite x (≡ 2p_L^c.m./√s) is (1/σ^{T,L))d3σT,L/E?}d³p ～ (1/q²) F(x,p_⊥²/q²) and thus the transverse momentum grows like q², whereas in the parton model (1/σ^T,L)d³σ^T,L/E^?1d³p ～ F(x,p_⊥²). A related effect is the absence of two-jet structure in e⁺e^? annihilation. We believe that dual model results may give a more reliable indication of the deep inelastic behaviour for composite hadrons than the parton model.     

Parity nonconserving nucleon-nucleon scattering (one-boson-exchange) in the weinberg-salam model

In the present paper we discuss the implications of the Weinberg-Salam model of weak interactions for parity non-conserving nucleon-nucleon scattering. The one-boson-exchange nucleon-nucleon potentials are determined by the use of the factorization method and current algebra. The effect of the neutral hadronic currents is to enhance both the pion contribution $\text{(Δ}\text{I}\text{?}\text{=1)}$ and the vector meson contribution (ΔI=0, (2))). The Weinberg-Salam model is consistent with the recent experiment on ¹⁹F and leads to a sizable measurable polarization effect in the transition 0^-, 0(1.08 MeV) to the ground state of ¹⁸F, namely, P ～ 5 × 10^?3.     

Pion distributions in inelastic neutrino interactions

Using data on semi-inclusive pion electroproduction as input we calculate in the framework of the quark parton model the distribution of pions in the current fragmentation region for inelastic neutrino interactions. Results for the π⁺/π^? asymmetry are presented for both charged and neutral currents. These provide stringent tests of the parton fragmentation hypothesis and the Weinberg-Salam gauge model.     

Parity-nonconservation effect in the helicities of conversion electrons accompanying the (5/2)− → (5/2)+ nuclear transition in the 229Pa nucleus

The ground state of the ²²⁹Pa nucleus is a 5/2^± doublet with a splitting energy of 220±50 eV. Such levels are peculiar to nuclei in the mass region around A=225 that are characterized by octupole deformations. A direct observation of P-odd effects in this system is of great interest because this can furnish information about the parity-nonconserving nucleon-nucleon potential. The transition between the two doublet states of opposite parities proceeds predominantly through internal conversion; therefore, P-odd mixing can be explored by studying the helicities of the conversion electron. It is shown that the helicities of the 6s _1/2, 6p _1/2, and 6p _3/2 conversion electrons are about 1%, which makes it possible to perform experiments aimed at determining the parameters of the effective parity-nonconserving nuclear potential.     

Measuring the P-odd asymmetry in electroproduction of the δ(32, 32 resonance at low energies

We show that measurements of the P-odd asymmetry in the reaction $\text{e}{}^{\mathrm{?}}\text{+}\text{N}\text{→}\text{e}{}^{\mathrm{?}}\text{+δ(}\text{2}\text{2}\text{,}\text{3}\text{2}$ at low energies might determine the combination $\text{α}\text{～}\text{+(1.0–1.2γ}\text{β}\text{～}$ of the isovector phenomenological couplings, characterizing the parity nonconserving electron-quark neutral current interaction at presently accessible energies. They may provide also a very accurate determination of the parameter sin²θ_W of the standard electroweak gauge theory.     

Current and constituent quarks: Their implications for resonance excitations polarized and unpolarized inelastic structure functions

The transformation between constituent and current quarks is discussed and applied to the calculation of matrix elements for nucleon to resonance transitions induced by arbitrary currents belonging to an octet. In particular, previous results on πN and γN transitions are subsumed while weak interactions (ΔQ = 0 or 1) and longitudinal photon induced transitions are discussed for the first time. The implications of a non-trivial Melosh transformation upon previous calculations in quark parton models of the non-diffractive component of the deep inelastic structure functions are discussed. The magnitudes of the unpolarized structure functions are found to be unchanged but for the polarized structure functions significant corrections to previous calculations are discovered. In particular it is found that it is not necessary that the polarization asymmetry A^γP be positive in the deep inelastic region. Our approach is valid for all Q², even for photoproduction, and is not restricted to deep inelastic scattering in contrast to earlier parton model calculations. The saturation of various current algebra sum rules is discussed.     

Linear and nonlinear optical spectroscopy of gadolinium iron borate GdFe<Subscript>3</Subscript>(BO<Subscript>3</Subscript>)<Subscript>4</Subscript>

The optical spectra and the second-harmonic generation (SHG) are studied in a noncentrosymmetric GdFe₃(BO₃)₄ magnet. In the region of weak absorption (α～20–400 cm^?1) below ～3 eV, three absorption bands are distinguished, which can be unambiguously assigned to forbidden electronic transitions from the ground ⁶A₁ state of the Fe³⁺ ion to its excited states ⁴T₁(～1.4 eV), ⁴T₂(～2 eV), and ⁴A₁, ⁴E(～2.8 eV). Intense absorption begins in the region above 3 eV (α～2–4×10⁵ cm^?1), where two bands at ～4.0 and 4.8 eV are observed, which are caused by allowed electric dipole charge-transfer transitions. The spectral features of SHG in the 1.2–3.0-eV region are explained by a change in the SHG efficiency caused by a change in the phase mismatch. It is shown that in the weak absorption region, phase matching can be achieved for SHG.