2nd Class Currents in Neutrino Reactions

The influence of 2nd class currents in neutrino reactions is investigated. We show that WEINBERG'S unified model of electromagnetic and weak interactions implies both neutral and 2nd class currents. Possible experimental effects due to 2nd class neutral weak currents are discussed. Further, we investigate implications of 2nd class charged currents for hadronic neutral weak currents. It is shown that if 2nd class charged currents exist, the isospin I = 1 axial-vector neutral current must be a “new” current, or it must contain a “new” I = 1 part. 2nd class charged currents are excluded if the I = 1 axial-vector neutral current is “old”, i.e., if it is proportional to the third component of the charged current. Then also the proportionality constant is real. CP invariance is assumed throughout the discussion.     

Parity violating flavour changing neutral current and natural conservation of strangeness in vector-like theories

Two vector-like schemes of the weak interactions, based on five and seven quarks, respectively, are studied in which the suppression of |ΔS| = 1 neutral currents is natural and in which the neutral current interaction violates parity. Various aspects (parity violation, flavour changing neutral current, “$\text{ν}$ anomaly”, masses of the W and Z bosons) are investigated.     

Investigating the QED vacuum with ultra-intense laser fields

In view of the increasingly stronger available laser fields it is becoming feasible to employ them to probe the nonlinear dielectric properties of the vacuum as predicted by quantum electrodynamics (QED) and to test QED in the presence of intense laser beams. First, we discuss vacuum-polarization effects that arise in the collision of a high-energy proton beam with a strong laser field. In addition, we investigate the process of light-by-light diffraction mediated by the virtual electron-positrons of the vacuum. A strong laser beam “diffracts” a probe laser field due to vacuum polarization effects, and changes its polarization. This change of the polarization is shown to be in principle measurable. Also, the possibility of generating harmonics by exploiting vacuum-polarization effects in the collision in vacuum of two ultra-strong laser beams is discussed. Moreover, when two strong parallel laser beams collide with a probe electromagnetic field, each photon of the probe may interact through the “polarized” quantum vacuum with the photons of the other two fields. Analogously to “ordinary” double-slit set-ups involving matter, the vacuum-scattered probe photons produce a diffraction pattern, which is the envisaged observable to measure the quantum interaction between the probe and strong field photons. We have shown that the diffraction pattern becomes visible in a few operating hours, if the strong fields have an intensity exceeding 10²⁴W/cm².     

Parton-nucleon reciprocity and the fragmentation of weak currents

We discuss some consequences of the parton-nucleon reciprocity relation for the production of nucleons by fragmentation of weak currents, both neutral and charged.     

Partons and gravitation: Some puzzling questions

The rather general belief in the theory of gravitation according to which neutral massive bodies with zero electric and magnetic moments are surrounded by a null electromagnetic field is analyzed from a critical viewpoint. Beginning the analysis at an atomic level, it is not difficult to see that neutral atoms are surrounded by a nonnull electromagnetic field generated by their peripheral electrons and by their nuclei even though their overall charge is zero. The data emerging from recent deep inelastic e-p scattering experiments clearly indicate that nucleons are composed by a number of charged constituents, often called partons, in a highly dynamical behavior.Consequently, nucleons and nuclei can also be a rather relevant source of electromagnetic field, in view of the presumed large number of partons, which is produced not only by their overall charges, but more properly by the charges of their individual constituents. Summing up the contributions from a large number of atoms, the possibility of a seizable electromagnetic field surrounding any neutral massive body emerges. Three assumptions, termed standard, weak, and strong according to which the energy-momentum tensor of the electromagnetic field generated by the matter constituents does not contribute, or partially contribute, or is entirely responsible of the gravitational field, are introduced. In order to assess the physical relevance of each of the above assumptions, a simple bound state model of the π⁰ particle is introduced in terms of two charged valence partons in a ¹S state. Some models of the electromagnetic field produced by the π⁰ charged constituents are derived as a ground for further extension to the case of nucleons, nuclei, and entire atoms. The gravitational field equations for the π⁰ particle according to the standard assumption are recalled and the ones according to the weak and strong assumptions are introduced. The puzzling implications of our analysis clearly cast shadows on the standard assumption, leaving as possible alternative for an exact formulation a selection between the weak and the strong assumptions. Some implications of the latter assumptions are discussed; the restrictions for the exterior case are derived using the framework of the “already unified theory”; some inconsistency with the gravitational wave theory is briefly discussed; and it is emphasized that the strong assumption implies a fully geometrical unification of gravitational and electromagnetic fields since the gravitational field is identified with a particular form, or “mutation,” of the electromagnetic field originated primarily in the nuclear, but also in the atomic structure. The admissibility of both the weak and the strong assumptions on the basis of our present knowledge is discussed and the feasibility of some experiments aiming at the proper selection as well as the ultimate physical assessment of the new assumptions is briefly analyzed.     

Single-pion production and the structure of the weak neutral current

We investigate the restrictions on the structure of the weak neutral current imposed by single pion production cross sections on single nucleons. A general vector (V), axial-vector (A) neutral current with |ΔI|?1 is assumed, where the isovector V,A neutral currents are the neutral members of the isotriplets containing the charged weak currents. From neutrino cross sections alone we derive bounds for the neutral current coupling constants. These bounds supplement the known constraints from inclusive scattering in a very useful way. More specific assumptions about the isoscalar neutral current are also considered. We discuss the resulting bounds using the existing neutrino data. Finally, it is shown that with the advent of antineutrino data for single pion production the neutral current coupling constants will be determined uniquely.     

Self-consistent renormalized phonons in metallic and nonmetallic solids

The interaction of charged particle beam with non-linear “cubic” type media has been studied; the dielectric permeability of such media depends on the square strength of the electric field produced by the beam-excited wave. The processes of the Cherenkov excitation of the medium by a modulated definite current are investigated as well as the polarization of longitudinal oscillations of the medium excited by the current. The equations are obtained to determine the dependence of fields excited by the current on the amplitude of the exciting current. It is found that under certain circumstances (near the radiation cut-off) the conditions of Cherenkov radiation may be violated due to non-linearities of the medium and the particle radiation loss vanish. The amplification of longitudinal waves in an arbitrary isotropic medium with “cubic” non-linearity by a monoenergetic particle beam is studied when the frequencies of amplified oscillations are close to the resonance frequencies of the medium.     

Polarized deuterons and protons at NICA@JINR

The novel scheme of proton and deuteron polarization control in the NICA collider at Dubna is proposed. By means of two Siberian Shakes with solenoid magnetic field the beam spin tune is shifted to the “zero” spin resonance vicinity, whereas manipulation of the polarization is realized by “weak” field solenoids. The scheme makes it possible to obtain any desired direction of the polarization in the both MPD and SPD detectors for any sort of the particles. The possibility of the beam polarization control in the orbit plane at any azimuth of the collider magnetic arcs exists also. The last gives necessary flexibility of optimal matching the beam polarization at injection into collider and at the polarimetery monitor points.     

基于非线性光纤环镜的40Gb/s可重构光逻辑门

提出了一种新型的基于非线性光纤环镜(NOLM)的可重构全光逻辑门实现方案。传统的基于NOLM的全光逻辑利用自相位调制效应或交叉相位调制效应,透射传输函数重构的自由度低,可实现的逻辑门种类较少。该方案在传统的结构基础上,分析了NOLM中探测光的偏振态的演化,以及输入光偏振态和环内偏振控制器对NOLM的传输特性的影响。理论分析和数值仿真结果表明在考虑NOLM中的非线性偏振旋转效应的情况下,可以更加自由地构建不同透射传输函数,从而利用单一NOLM结构,仅通过调节偏振控制器,即能够可重构地实现绝大部分基础组合逻辑。实验中,完成了两路40Gb/s的数据信号之间的"非"、"与"、"或"、"或非"、"同或"、"异或"等各种基础组合逻辑,验证了方案的可行性。     

On some tests of the basic properties of the neutral weak interaction. I. With massless neutrinos

We consider the Born approximation scattering, by electrons, of neutrinos (and antineutrinos) of the muon and of the electron types; the general Lagrangian respecting lepton locality is used. Throughout, we study only differential cross sections as the experimental observables. Some tests previously proposed for “neutrino identity” or Lorentz structure of the neutral weak interaction are reexamined. We find that, in general, these relations cannot uniquely answer the question of Lorentz structure. Similarly, in general, one cannot estblish whether the final neutral lepton is completely identical with, or “partly identical” with, or completely different from, the initial neutrino; identity allows a difference in helicity. In several experimental situations, one can exclude the possibility of a complete non-identity. In one experimental situation, assuming μe universality, one can establish that the final and the initial neutrinos are completely identical, even in their helicity. “Does an interference between neutral currents and the (V ? A) charged current exist in

e^- scattering?” Certain tests can answer this question completely if μe universality is assumed. Without μe universality, the answer is “destructive interference” if an observable (A_e) turns out to be less than 4; A_e = 4 would exclude a constructive interference. Assuming neutrino identity, time-reversal invariance for the helicity flipping types (S,P,T), and μe universality, certain simple combinations of observables were previously noted to determine the (V,A) neutral interaction couplings of the neutrino to the electron. With our general formalism, that determination is seen not to require the first two assumptions. Also, the couplings concerned are seen to be only the “diagonal” ones—which refer to that part of the final state in which the final neutrino is identical with the iniitial one. Keeping in view a recent experimental situation, the following question is answered: “When will the lack of enough events for $\text{ν}\text{e}{}^{\mathrm{?}}$ scattering (or, similarly, νe^? scattering) become a threat to lepton locality?” Some additional consequences of μe universality are noted.     

Possibility of distinguishing the effect of neutral weak currents in e+e− → μ−μ+ experiments with longitudinally polarized clashing beams

The process e⁺e^{– – +} for the case of longitudinal polarization of the initial and final particles is studied on the basis of several models: the Weinberg-Salam model, the Lee-Prentki-Zumino model, the vector model, the X model, and under the assumption of a V-A structure of the neutral weak currents. Polarization effects tn the differential and total cross sections for this process are analyzed in detail, and various possibilities for distinguishing the contribution of neutral weak currents are found. Calculations show that neutral weak currents lead to appreciable polarization effects at attainable energies and that these effects are very sensitive to the model. It is important to note that an experimental study of these effects can yield valuable information on not only the structure of the neutral weak currents but also the sign of the weak-interaction constant.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 31–36, April, 1978.The authors thank A. A. Sokolov for a useful discussion and for interest in this work.     

A U(3) nonet scheme for leptons

Introducing six new heavy leptons, we construct a U(3) scheme for leptons. The leptonic U(3) is exactly parallel to the hadronic U(3). One may also introduce quark-like leptonic triplets. A “natural” value of 60° emerges for the mixing angle with m_w = 53 GeV in a theory of weak and electromagnetic interaction based on this U(3) symmetry. There are no neutral ΔS_l = 0 neutrino currents.     

Electron-beam-induced polarization of lithium- and manganese-modified lead ferroniobate ceramics and its respective emission phenomena

A polarization state is formed with an electron beam in ceramic samples of pure lead ferroniobate (PFN) and PFN modified to a superstoichiometric composition at the stage of synthesis by adding 1 wt % lithium carbonate (PFNL) and 1 wt % of magnesia (PFNM). It is shown that in the case of PFNL, polarization by an electron beam is more efficient than the conventional method of “hot” polarization. Reasons for the observed effects, including enhanced electron emission from local irradiated areas on the surface of the ceramics, are discussed.     

Stokes parameters of γ-quanta in the e+ + e− → Z + γ reaction

A general analysis is made of the polarization properties of γ-quanta in the e⁺ + e^? → Z + γ reaction. Besides the standard mechanism of this reaction; which is determined by the eeZ interaction (neutral weak currents), the possible anomalous magnetic moment χ of the Z boson is also taken into account. A linear contribution in χ. to the differential cross section of the e⁺ + e^? → Z + γ process (with unpolarized particles in the initial and final states) leads to CP-odd asymmetry of the angular distribution of γ-quanta relative to the substitution cos Θ→?cos Θ, where Θ is the angle of emission of the γ-quantum relative to the electron. Measurement of this asymmetry with an accuracy of the order of 1% makes it possible to get a “sense” of the contribution of the magnetic moment of a Z boson of the order of 10^?3 GeV^?1.     

Symmetry behavior in gauge theories

A theory of phase transition with symmetry restoration in gauge theories at high temperature is investigated. The phase transition may be of the first or of the second order depending on relations between coupling constants. It is noted that the possible existense of a limiting temperature cannot prevent the high-temperature symmetry restoration. In the theories without neutral currents, symmetry also can be affected by a magnetic field. However in most of the models with neutral currents symmetry restoration takes place not due to a magnetic field but due to massive vector fields, created simultaneously by the magnetic field sources. It is pointed out that in most of the theories with neutral currents an increase of external currents lead to symmetry restoration, while an increase of density results in a further increase of symmetry breaking. In some cases critical values of temperature and external fields and currents appear to be extremely small. At certain relations between coupling constants radiative corrections lead to the absence of symmetry breaking in gauge theories even at zero temperature and in the absence of any other external factors. Strong constraints on masses and coupling constants for the symmetry in the Higgs model to be broken are obtained. It is shown that energy of substance is nonconserved due to energy “pumping” from the non-observable Bose-condensate in the processes under consideration.     

Measurements of neutron interference and polarization effects caused by nuclear and magnetic interaction

The effects of simultaneous phase shift and spin rotation on neutron waves were measured with the perfect crystal neutron interferometer. Using an unpolarized beam of slow neutrons characteristic “beat” effects of the interference pattern and a polarization of the neutrons behind the interferometer could be observed.     

Pion production by fragmentation of weak currents in Weinberg theory

The Feynman quark parton model is used to study inclusive single-pion production by the fragmentation of the neutral and charged weak currents of Weinberg theory. The structure functions for the neutral current-induced reactions are related to those for the electromagnetic and charged weak current processes. Analogues of inclusive deep-inelastic sum rules are derived. The ratios of neutral current to charged current cross sections for semi-inclusive pion production are studied. In the approximation of neglect of “core” partons, these ratios are given in terms of average pion multiplicities in the charged current-induced reaction. We finally specialise to the quark parton distributions of McElhaney and Tuan to calculate these ratios as functions of the Weinberg angle.     

Interaction of a modulated electron beam with a magnetoactive plasma

Experimental results concerning the interaction of a modulated electron beam with a magnetoactive plasma in the whistler frequency range are reported. It was shown experimentally that when a beam is injected into the plasma, waves can be generated by two possible mechanisms: Cherenkov emission of whistlers by the modulated beam, and transition radiation from the beam injection point. In the case of weak beam currents (N _b/N ₀)≪⁻⁴) the Cherenkov resonance radiation is more than an order of magnitude stronger than the transition radiation; the Cherenkov emission efficiency decreases at high beam currents. The transformation of the distribution function of the beam is investigated for the case of weak beam currents. It is shown that in the case of the Cherenkov interaction with whistlers the beam is retarded and the beam distribution function becomes wider and acquires a plateau region. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 6, 378–382 (25 March 1998)     

Stationary state currents in nuclear reactions: Rotational coupling in alpha-particle scattering

The graphical presentation of stationary-state probability currents occuring in nuclear reactions is described, and some results are presented for an alpha-scattering example involving channel coupling. We find that a natural way of expressing channel coupling effects is through the introduction of non-spherical potentials (“ψ-potentials”) which precisely reproduce the elastic-scattering channel wavefunction. The relationship to more conventional coupling-induced polarization potentials is discussed and arguments presented for an “anti-Perey” effect related to channel coupling non-locality.     

Semi-leptonic weak and electromagnetic interactions in nuclei:: Parity violations in electron scattering and weak neutral currents

A general result for the difference in differential cross sections for electron scattering between any two nuclear levels with incident longitudinally polarized right- and left-handed electrons is derived. This difference must involve the parity-violating weak interaction at least linearly and can be used to study weak neutral currents as pointed out by Feinberg. A V — A structure for the weak neutral currents is assumed with a semi-leptonic current-current interaction, and the electromagnetic interaction is treated in the one-photon-exchange approximation. The result is expressed in terms of the same set of reduced matrix elements of the multipoles of the nuclear currents which govern all electromagnetic and weak transitions between these levels. A previously developed unified analysis of semi-leptonic weak and electromagnetic interactions in nuclei which determines one-body transition densities, including their spin and spatial dependences, through electron scattering provides nuclear transitions to serve as known analyzers in testing the structure of this part of the weak interaction. Examples are given using Weinberg's model of the weak neutral currents. Feinberg's result for elastic scattering from spin-0 nuclei is rederived and two new examples using previously determined one-body densities are discussed : the 1⁺0 → 0⁺1 (3.56 MeV) transition in ⁶Li and the 0⁺0 → 1⁺ 1(15.1 MeV) transition in ¹²C.