arXiv subjects

A. N. Ivanov

Publications and source records attributed to A. N. Ivanov.

At least 37 records · Page 2Linked to original sources

arXiv2018

Neutron Dark Matter Decays

We analyse the discrepancy between the neutron lifetimes measured in the bottle and beam experiments. Following Fornal and Grinstein (Phys. Rev. Lett. 120, 191801 (2018)) we propose an explanation of such a puzzle by the dark matter channels of the neutron decay. However, unlike Fornal and Grinstein in addition to the dark matter decay channel n -> χ+ e^- + e^+, where χis a dark matter Dirac fermion and (e^-e^+) is an electron--positron pair, we assume the existence of the dark matter channel n -> chi + ν_e + \barν_e, where ν_e \barν_e is the electron neutrino-antineutrino pair. This allows to describe the discrepancy between the measurements of the neutron lifetime even in case of an unobservability of the dark matter decay channel n -> χ+ e^- + e^+, which may be below the reaction threshold. The existence of the coupling n -> χ+ e^- + e^+ can be observed experimentally by measuring electron-neutron scattering e^- + n -> χ+ e^- at very low electron energies, induced with the strength as of the decay n -> χ+ ν_e + \barν_e$. We propose a gauge invariant quantum field theory model with SU_L(2)\times U_R(1) \times U_R'(1)\times U''_L(1) symmetry for the UV completion of the effective (nχ\ell \bar{\ell}) interaction, where \ell(\bar{\ell}) is electron (positron) or neutrino(antineutrino).

hep-ph↗

arXiv2018

Infrared Properties of Hadronic Structure of Nucleon in Neutron Beta Decays to Order O(α/π) in Standard V - A Effective Theory with QED and Linear Sigma Model of Strong Low--Energy Interactions

Within the standard V - A theory of weak interactions, Quantum Electrodynamics (QED) and the linear sigma-model (LsM) of strong low-energy hadronic interactions we analyse infrared properties of hadronic structure of the neutron and proton in the neutron beta decays to leading order in the large nucleon mass expansion. We confirm validity and high confidence level of contributions of hadronic structure of the nucleon to the radiative corrections, calculated by Sirlin (Phys. Rev. 164, 1767 (1967)) to leading order in the large nucleon mass expansion. At the level of order 10^{-5} relative to Sirlin's infrared divergent contribution to the neutron radiative beta decay (inner bremsstrahlung) we find an infrared divergent contribution, induced by hadronic structure of the nucleon through the one-pion-pole exchange, to the rate of the neutron lifetime from the neutron radiative beta decay, which should be cancelled by contributions of virtual photon exchanges to the neutron beta decay. Following Ivanov et al. 1805.09702 [hep-ph] we argue that a consistent analysis of such a cancellation may be carried out well in the combined quantum field theory including the Standard Electroweak Model (SEM) and the LsM of strong low-energy interactions, where the effective V - A hadron-lepton current-current vertex is caused by the W^- - electroweak-boson exchange.

hep-ph↗

arXiv2018

Gauge and Infrared Properties of Hadronic Structure of Nucleon in Neutron Beta Decay to Order O(α/π) in Standard V - A Effective Theory with QED and Linear Sigma Model of Strong Low--Energy Interactions

Within the standard V - A theory of weak interactions, Quantum Electrodynamics (QED) and the linear sigma-model (LsM) of strong low-energy hadronic interactions we analyse gauge and infrared properties of hadronic structure of the neutron and proton in the neutron beta decay to leading order in the large nucleon mass expansion. We show that the complete set of Feynman diagrams describing radiative corrections of order O(α/π), induced by hadronic structure of the nucleon, to the rate of the neutron beta decay is gauge non-invariant and unrenormalisable. We show that a gauge non-invariant contribution does not depend on the electron energy in agreement with Sirlin's analysis of contributions of strong low-energy interactions (Phys. Rev. 164, 1767 (1967)). We show that infrared divergent and dependent on the electron energy contributions from the neutron radiative beta decay and neutron beta decay, caused by hadronic structure of the nucleon, are cancelled in the neutron lifetime. Nevertheless, we find that divergent contributions of virtual photon exchanges to the neutron lifetime, induced by hadronic structure of the nucleon, are unrenormalisable even formally. Such an unrenormalizability can be explained by the fact that the effective V - A vertex of hadron-lepton current-current interactions is not a vertex of the combined quantum field theory including QED and LsM, which are renormalizable theories.

hep-ph↗

arXiv2018

Gauge Properties of Hadronic Structure of Nucleon in Neutron Radiative Beta Decay to Order O(alpha/pi) in Standard V - A Effective Theory with QED and Linear Sigma Model of Strong Low--Energy Interactions

Within the standard V - A theory of weak interactions, Quantum Electrodynamics (QED) and the linear sigma-model (LsM) of strong low-energy hadronic interactions we analyse gauge properties of hadronic structure of the neutron and proton in the neutron radiative beta-decay. We show that the Feynman diagrams, describing contributions of hadronic structure to the amplitude of the neutron radiative beta-decay in the tree-approximation for strong low-energy interactions in the LsM, are gauge invariant. In turn, the complete set of Feynman diagrams, describing the contributions of hadron-photon interactions in the one-hadron-loop approximation, is not gauge invariant. In the infinite limit of the scalar sigma-meson, reproducing the current algebra results (Weinberg, Phys. Rev. Lett. 18, 188 (1967)), and to leading order in the large nucleon mass expansion the Feynman diagrams, violating gauge invariance, do not contribute to the amplitude of the neutron radiative beta-decay in agreement with Sirlin's analysis of strong low-energy interactions in neutron beta decays. We assert that the problem of appearance of gauge non-invariant Feynman diagrams of hadronic structure of the neutron and proton is related to the following. The vertex of the effective V-A weak interactions does not belong to the combined quantum field theory including the LsM and QED. We argue that gauge invariant set of Feynman diagrams of hadrons, coupled to real and virtual photons in neutron beta decays, can be obtained within the combined quantum field theory including the Standard Electroweak Model (SEM) and the LsM, where the effective V-A vertex of weak interactions is a result of the W^- - electroweak boson exchange.

hep-ph↗

arXiv2017

Lorentz Structure of Vector Part of Matrix Elements of Transitions n <-> p, Caused by Strong Low-Energy Interactions and Hypothesis of Conservation of Charged Vector Current

We analyse the Lorentz structure of the matrix elements of the transitions "neutron <-->proton", induced by the charged hadronic vector current. We show that the term maintaining conservation of the charged hadronic vector current even for different masses of the neutron and proton (see T. Leitner et al., Phys. Rev. C 73, 065502 (2006) and A. M. Ankowski, arXiv:1601.06169 [hep-ph]) has a dynamical origin, related to the G-even first class current contribution. We show that because of invariance of strong low-energy interactions under the G-parity transformations, the G-odd contribution with the Lorentz structure $q_μ$, where $q_μ$ is a momentum transferred, does not appear in the matrix elements of the ``neutron <-> proton' transitions.

hep-ph↗

arXiv2017

Precision Theoretical Analysis of Neutron Radiative Beta Decay to Order "O(α^2/π^2)"

In the Standard Model (SM) we calculate the decay rate of the neutron radiative beta decay to order "O(α^2/π^2 ~ 10^{-5})", where "α$"is the fine--structure constant, and radiative corrections to order "O(α/π~ 10^{-3})". The obtained results together with the recent analysis of the neutron radiative beta decay to next-to-leading order in the large proton-mass expansion, performed by Ivanov et al. Phys. Rev. D95, 033007 (2017), describe recent experimental data by the RDK II Collaboration (Bales et al., Phys. Rev. Lett. 116, 242501 (2016)) within 1.5 standard deviations. We argue a substantial influence of strong low-energy interactions of hadrons coupled to photons on the properties of the amplitude of the neutron radiative beta decay under gauge transformations of real and virtual photons.

hep-ph↗

arXiv2017

Comment on "On the implementation of CVC in weak charged-current proton-neutron transitions" by C. Giunti, arXiv: 1602.00215 [hep-ph]

We show that the term maintaining conservation of the charged vector current for the transitions "neutron <-> proton" even for different masses of the neutron and proton (see T. Leitner et al., Phys. Rev. C {\bf 73}, 065502 (2006) and A. M. Ankowski, arXiv:1601.06169 [hep-ph]) is related to the first class current contribution but not to the second class one as has been pointed out by C. Giunti, arXiv: 1602.00215 [hep-ph].

hep-ph↗

arXiv2017

Precision Theoretical Analysis of Neutron Radiative Beta Decay

In the Standard Model of electroweak interactions and in the tree--approximation we calculate the rate and branching ratio of the neutron radiative beta decay with one-real photon emission by taking into account the contributions of the weak magnetism and proton recoil to order 1/m_p of the large proton mass m_p expansion. We find that the obtained contributions of the weak magnetism and proton recoil increase the rate and branching ratio of the neutron radiative beta decay by about 0.70%. This is large compared with the contribution of the weak magnetism and proton recoil of about 0.16% to the rate of the neutron beta decay, calculated in Phys. Rev. D88, 073002 (2013).

hep-ph↗

arXiv2016

Parity-Even and Time-Reversal-Odd Neutron Optical Potential in Spinning Matter Induced by Gravitational Torsion

Recent theoretical work has shown that spin $1/2$ particles moving through unpolarized matter which sources torsion fields experience a new type of parity-even and time-reversal-odd optical potential if the matter is spinning in the lab frame. This new type of optical potential can be sought experimentally using the helicity dependence of the total cross sections for longitudinally polarized neutrons moving through a rotating cylindrical target. In combination with recent experimental constraints on short-range P--odd, T--even torsion interactions derived from polarized neutron spin rotation in matter one can derive separate constraints on the time components of scalar and pseudoscalar torsion fields in matter. We estimate the sensitivity achievable in such an experiment and briefly outline some of the potential sources of systematic error to be considered in any future experimental search for this effect.

nucl-ex↗

arXiv2016

Einstein-Cartan Gravity with Torsion Field Serving as Origin for Cosmological Constant or Dark Energy Density

We analyse the Einstein-Cartan gravity in its standard form cal-R = R + cal-K^2, where cal-R and R are the Ricci scalar curvatures in the Einstein-Cartan and Einstein gravity, respectively, and cal-K^2 is the quadratic contribution of torsion in terms of the contorsion tensor cal-K. We treat torsion as an external (or a background) field and show that the contribution of torsion to the Einstein equations can be interpreted in terms of the torsion energy-momentum tensor, local conservation of which in a curved spacetime with an arbitrary metric or an arbitrary gravitational field demands a proportionality of the torsion energy--momentum tensor to a metric tensor, a covariant derivative of which vanishes because of the metricity condition. This allows to claim that torsion can serve as origin for vacuum energy density, given by cosmological constant or dark energy density in the Universe. This is a model-independent result may explain a small value of cosmological constant, which is a long--standing problem of cosmology. We show that the obtained result is valid also in the Poincare' gauge gravitational theory by Kibble (T. W. B. Kibble, J. Math. Phys. 2, 212 (1961)), where the Einstein-Hilbert action can be represented in the same form cal-R = R + cal-K^2.

gr-qc↗

arXiv2016

Exact Solution for Chameleon Field, Self-Coupled Through the Ratra-Peebles Potential with n = 1 and Confined Between Two Parallel Plates

We calculate the chameleon field profile, confined between two parallel plates, filled with air at pressure $P = 10^{-4}\,{\rm mbar}$ and room temperature and separated by the distance $L$, in the chameleon field theory with Ratra--Peebles self--interaction potential with index $n = 1$. We give the exact analytical solution in terms of Jacobian elliptic functions, depending on the mass density of the ambient matter. The obtained analytical solution can be used in qBounce experiments, measuring transition frequencies between quantum gravitational states of ultracold neutrons and also for the calculation of the chameleon field induced Casimir force for the CANNEX experiment. We show that the chameleon--matter interactions with coupling constants $β\le 10^4$ can be probed by qBounce experiments with sensitivities $ΔE \le 10^{-18}\,{\rm eV}$. At $L = 30.1\,{\rm μm}$ we reproduce the result $β< 5.8\times 10^8$, obtained by Jenke {\it et al.} Phys. Rev. Lett. {\bf 112}, 151105 (2014)) at sensitivity $ΔE \sim 10^{-14}\,{\rm eV}$. In the vicinity of one of the plates our solution coincides with the solution, obtained by Brax and Pignol (Phys. Rev. Lett. {\bf 107}, 111301 (2011)) (see also Ivanov {\it et al.} Phys. Rev. D {\bf 87}, 105013 (2013)) above a plate at zero density of the ambient matter.

gr-qc↗

arXiv2016

Spin Precession of Slow Neutrons in Einstein-Cartan Gravity with Torsion, Chameleon and Magnetic Field

We analyse a spin precession of slow neutrons in the Einstein-Cartan gravity with torsion, chameleon and magnetic field. For the derivation of the Heisenberg equation of motion of the neutron spin we use the effective low-energy potential, derived by Ivanov and Wellenzohn (Phys. Rev. D92, 125004 (2015)) for slow neutrons, coupled to gravitational, chameleon and torsion fields to order 1/m, where m is the neutron mass. In addition to this low-energy interactions we switch on the interaction of slow neutrons with a magnetic field. We show that to linear order approximation with respect to gravitational, chameleon and torsion fields the Dirac Hamilton operator for fermions (neutrons), moving in spacetimes created by rotating coordinate systems, contains the anti-Hermitian operators of torsion-fermion (neutron) interactions, caused by torsion scalar and tensor degrees of freedom. Such anti-Hermitian operators violate CP and T invariance. One may assume that in the rotating Universe and galaxies the obtained anti-Hermitian torsion-fermion interactions might be an origin of i) violation of CP and T invariance in the Universe and ii) of baryon asymmetry.

gr-qc↗

arXiv2015

Effective Low-Energy Gravitational Potential for Slow Fermions Coupled to Linearised Massive Gravity

We analyse the Dirac equation for slow fermions coupled to linearised massive gravity above the Minkowski background and derive the effective low-energy gravitational potential. The obtained results can be used in terrestrial laboratories for the detection of gravitational waves and fluxes of massive gravitons emitted by cosmological objects. We also calculate the neutron spin precession within linearised massive gravity, which in principle can be measured by neutron interferometers.

gr-qc↗

arXiv2015

Effective Low-Energy Potential for Slow Dirac Fermions in Einstein-Cartan Gravity with Torsion and Chameleon

We derive the most general effective low-energy potential to order O(1/m) for slow Dirac fermions with mass m, coupled to gravitational, chameleon and torsion fields in the Einstein-Cartan gravity. The obtained results can be applied to the experimental analysis of gravitational, chameleon and torsion interactions in terrestrial laboratories. We discuss the use of rotating coordinate systems, caused by rotations of devices, for measurements of the torsion vector and tensor components, caused by minimal torsion--fermion couplings (Ivanov and Wellenzohn, Phys. Rev. D92, 065006 (2015)). Using the most general form of a metric tensor of curved spacetimes in rotating coordinate systems, proposed by Obukhov, Silenko, and Teryaev (Phys. Rev. D84, 024025 (2011)), we extend this metric by the inclusion of the chameleon field and calculate the set of vierbein fields, in terms of which Dirac fermions couple to torsion vector and tensor components through minimal torsion-fermion couplings. For such a set of vierbein fields we discuss a part of the effective low-energy potential for slow Dirac fermions, coupled to gravitational, chameleon and torsion fields to order O(1) in the large fermion mass expansion.

gr-qc↗

arXiv2015

Non-Relativistic Approximation of Dirac Equation for Slow Fermions Coupled to the Chameleon and Torsion Fields in the Gravitational Field of the Earth

We analyse a non-relativistic approximation of the Dirac equation for slow fermions, coupled to the chameleon field and torsion in the spacetime with the Schwarzschild metric, taken in the weak gravitational field of the Earth approximation. We follow the analysis of the Dirac equation in the curved spacetime with torsion, proposed by Kostelecky (Phys. Rev. D69, 105009 (2004)), and apply the Foldy--Wouthuysen transformations. We derive the effective low-energy gravitational potentials for slow fermions, coupled to the gravitational field of the Earth, the chameleon field and to torsion with minimal and non-minimal couplings.

gr-qc↗

arXiv2015

Standard Electroweak Interactions in Gravitational Theory with Chameleon Field and Torsion

We propose a version of a gravitational theory with the torsion field, induced by the chameleon field. Following Hojman et al. Phys. Rev. D17, 3141 (1976) the results, obtained in Phys. Rev. D90, 045040 (2014), are generalised by extending the Einstein gravity to the Einstein-Cartan gravity with the torsion field as a gradient of the chameleon field through a modification of local gauge invariance of minimal coupling in the Weinberg-Salam electroweak model. The contributions of the chameleon (torsion) field to the observables of electromagnetic and weak processes are calculated. Since in our approach the chameleon-photon coupling constant beta_(gamma) is equal to the chameleon-matter coupling constant beta, i.e. beta_(gamma) = beta, the experimental constraints on beta, obtained in terrestrial laboratories by T. Jenke et al. (Phys. Rev. Lett. 112, 115105 (2014)) and by H. Lemmel et al. (Phys. Lett. B743, 310 (2015)), can be used for the analysis of astrophysical sources of chameleons, proposed by C. Burrage et al. (Phys. Rev. D79, 044028 (2009)), A.-Ch. Davis et al. (Phys. Rev. D80, 064016 (2009), and in references therein, where chameleons induce photons because of direct chameleon-photon transitions in the magnetic fields.

gr-qc↗

arXiv2015

Neutron Interferometry constrains dark energy chameleon fields

We present phase shift measurements for neutron matter waves in vacuum and in low pressure Helium using a method originally developed for neutron scattering length measurements in neutron interferometry. We search for phase shifts associated with a coupling to scalar fields. We set stringent limits for a scalar chameleon field, a prominent quintessence dark energy candidate. We find that the coupling constant $β$ is less than 1.9 $\times10^7$~for $n=1$ at 95\% confidence level, where $n$ is an input parameter of the self--interaction of the chameleon field $φ$ inversely proportional to $φ^n$.

hep-ph↗

arXiv2014

GSI Oscillations as Laboratory for Testing of New Physics

We analyse recent experimental data on the GSI oscillations of the hydrogen-like heavy {^{142}}{\rm Pm}^{60+} ions that is a time modulation of the K-shell electron capture (EC) decay rate. We follow the mechanism of the GSI oscillations, caused by an interference of the neutrino flavour mass-eigenstates in a content of the electron neutrino. We give arguments that these experimental data show i) an existence of sterile neutrinos that is necessary for an explanation of a phase-shift, ii) an observation of CP violation, related to a phase-shift, and iii) an influence of the Quantum Zeno Effect, explaining different values of the amplitude and phase-shift for two runs of measurements with different time resolutions and different numbers of consecutive measurements.

hep-ph↗