Yu. V. Gaponov

Neutron beta decay and the right-handed currenr problem

Abstract The renormalization of the axial-vector coupling constant λ = g A / g V , extracted from the neutron lifetime ( λ τ ) and from the neutron beta decay asymmetry ( λ c ) is considered carefully In the standard model of the electroweak interaction λ τ should be equal to λ c . According to recent experimental data on neutron beta decay, λ τ and λ c seem to differ from each other. This fact is explained in the framework of the manifestly left-right symmetric model SU(2) L × SU(2) R × U(1). The possibility of the existence of the right-handed current in the neutron beta decay is pointed out. A joint analysis of neutron beta decay and muon decay is performed, the right-handed current parameters are estimated. The axial-vector constant renormalization ( λ N ) by right-handed currents is evaluated.

Radiative neutron β-decay and its possible experimental realization

Abstract The analysis of the modern status of neutron β-decay experiments demonstrates the necessity to investigate the process of the radiative free neutron β decay. The theoretical description of the process is discussed. An experiment is proposed.

Interaction of electron neutrinos with 56Fe in the LSD for E ⊻ ≤50 MeV

The neutrino pulses detected by the LSD (Liquid Scintillator Detector) on February 23, 1987, are analyzed on the basis of a two-stage model of supernova explosion. The number of events due to the electron-neutrino interaction with 56Fe in the LSD is calculated. The obtained number of signals is in agreement with experimental data.

S WAVE PION NUCLEON INTERACTION AND PCAC IN NUCLEAR MATTER

It is shown that the pion-nucleon σM-term contribution to the S-wave π-N interaction leads to a modification of the PCAC hypothesis in nuclear matter. Some experiments that enable one to obain directly the pion-nucleon σ-term, without any extrapolation to unphysical values of the kinematical variables, are discussed.

Giant Gamow-Teller resonance in neutron-rich nuclei

The giant Gamow-Teller resonance and other branches of collective nuclear excitations are described on the basis of the theory of finite Fermi systems. A connection between the Gamow-Teller resonance and Wigner SU(4) symmetry is proven. The beta-decay strength function and processes accompanying the β− decay of neutron-rich nuclei are described. The effect of the satellites of the Gamow-Teller resonance on the decay properties of neutron-rich nuclei is analyzed.

The radiative beta-decay mode of the free neutron

Abstract This report is dedicated to theoretical investigation of the rare, radiative neutron decay mode, which, unlike that of other elementary particles, has never been investigated experimentally. This new kind of neutron experiment allows us to directly test part of the radiative corrections, whose contribution is presently estimated at 1.5% of the total neutron β-decay probability. A comparison between the description of neutron radiative decay and nuclear radiative β-decay is given. Results of theoretical evaluations of radiative corrections, given in literature, are discussed.

Description of the majorana properties of neutral particles within pauli symmetry

A mathematical model that makes it possible to describe the Majorana properties of a system of free left-and right-handed neutral fermions belonging to the same type is constructed on the basis of transformations that include the chiral U (1) group and the Pauli SU (2) group, which mixes particle and antiparticle states. For massless particles, Pauli symmetry is exact and leads to conserved charges, a chiral and a generalized lepton one; the latter is a vector in Pauli isospace, where various directions are associated with Dirac or generalized Majorana properties. In the case of a nonzero mass, the scheme in question describes the combined Dirac-Majorana properties of particles belonging to A and B (ηP2 = −1) and C and D (ηP2 = 1) inversion classes, the condition ML = −MR being satisfied for their Majorana masses. For particles of C and D classes, the mass term in the Lagrangian and the Pauli charge can be related through the generalized-lepton-charge operator. For particles of A and B classes, these features are complementary, an alternative description of particles in terms of the lepton charge or two independent Majorana fields being possible in the Dirac case. In general, however, only representations of the latter type are realized, in which case the eigenvalues of the operator that determines the structure of the mass term in the Lagrangian serve as basic features.

Majorana properties of free particles in the Pauli symmetry scheme

Analysis of the Majorana properties of neutrino [1] is one of the key problems of the physics of weak processes. Majorana neutrino models have been developed in two variants: (i) in a variant initiated by Pontecorvo [2] with left and right (sterile) neutrinos and (ii) in a variant involving neutrinos of different generations [3, 4]. In the former variant, the neutrino Lagrangian includes Dirac (mD) and Majorana (mL, R) mass terms of the form [5–9]

Phenomenological Study of Solar-Neutrino-Induced ββ Process of 100Mo

The detection of solar-neutrinos of different origin via induced ββ process of 100Mo is investigated. The particular counting rates and energy distributions of emitted electrons are presented. A discussion in respect to the solar-neutrino detector consisting of 10 tones of 100Mo is included. Both the cases of the standard solar model and neutrino oscillation scenarios are analyzed. Moreover, new β-β+ and β-/EC channels of the double-beta process are introduced and possibilities of their experimental observation are addressed.

Precision analysis of experiments studying the beta decay of the free neutron: Standard model and possibilities of its violation

The current status of experimental results on the beta decay of the free neutron is described. An analysis of these data shows that, within the present-day accuracy, the data are fully consistent with the Standard Model of electroweak interaction. At the same time, there exists the possibility of deviations from the Standard Model at a level of 1%. The possible violations due to the contributions of right-handed (WR) bosons, as well as of leptoquark mechanisms introducing anomalous scalar and tensor terms in the effective weak-interaction Hamiltonian, which include the right-handed neutrinos, are estimated. In the last case, the analysis is performed by an analytic method that makes it possible to take into account, for the first time, the possibility of CP violation.