Anomalous Magnetic Moment Of Nucleon Research Articles

Effects of center-of-mass correction and nucleon anomalous magnetic moments on nuclear charge radii

Effects of center-of-mass correction and nucleon anomalous magnetic moments on nuclear charge radii

Effect of strong magnetic fields on the crust-core transition and inner crust of neutron stars

The Vlasov equation is used to determine the dispersion relation for the eigenmodes of magnetized nuclear and neutral stellar matter, taking into account the anomalous magnetic moment of nucleons. The formalism is applied to the determination of the dynamical spinodal section, a quantity that gives a good estimation of the crust-core transition in neutron stars. We study the effect of strong magnetic fields, of the order of $10^{15}-10^{17}$ G, on the extension of the crust of magnetized neutron stars. The dynamical instability region of neutron-proton-electron ($npe$) matter at subsaturation densities is determined within a relativistic mean field model. It is shown that a strong magnetic field has a large effect on the instability region, defining the crust-core transition as a succession of stable and unstable regions due to the opening of new Landau levels. The effect of the anomalous magnetic moment is non-negligible for fields larger than 10$^{15}$ G. The complexity of the crust at the transition to the core and the increase of the crust thickness may have direct impact on the properties of neutrons stars related with the crust.

The g – 2 muon anomaly in di-muon production with the torsion in LHC

It was considered within the framework of the conformal gauge gravitational theory CGTG coupling of the standard model fermions to the axial torsion and preliminary discusses the impact of extra dimensions, in particular, in a five-dimensional space-time with Randall–Sundrum metric, where the fifth dimension is compactified on an [Formula: see text] orbifold, which as it turns out is conformally to the fifth dimension flat Euclidean space with permanent trace of torsion, with a compactification radius [Formula: see text] in terms of the radius of a CGTG gravitational screening, through torsion in a process [Formula: see text] and LHC data. In general, have come to the correct set of the conformal calibration curvature the Faddeev–Popov diagram technique type, that follows directly from dynamics. This leads to the effect of restrictions on neutral spin currents of gauge fields by helicity and the Regge’s form theory. The diagrams reveals the fact of opening of the fine spacetime structure in a process [Formula: see text] with a center-of-mass energy of 14[Formula: see text]TeV, indicated by dotted lines and texture columns, as a result of p–p collision on [Formula: see text][Formula: see text]cm scales from geometric shell gauge bosons of the SM continued by the heavy axial torsion resonance, and even by emerging from the inside into the outside of the ultra-light (freely-frozen in muon’s spin) axial torsion. We then evaluate the contribution of the torsion to the muon anomaly to derive new constraints on the torsion parameters. It was obtained that on the [Formula: see text] scattering through the exchange of axial torsion accounting, the nucleon anomalous magnetic moment in the eikonal phase leads to additive additives which is responsible for the spin-flip in the scattering process, the scattering amplitude is classical and characterized by a strong the torsion coupling [Formula: see text]. So the scattering of particles, occurs as on the Coulomb center with the charge [Formula: see text] This is the base model which is the g[Formula: see text]2 muon anomaly. The muon anomaly contribution due to the heavy axial vector torsion arises from coupling the muon with torsion as external field. This leads to negative energy additive to mass of muons which makes the missing part of the g[Formula: see text]2 muon anomaly. It takes place at reasonable values of the transverse front size of the exact solution CGTG equations types of torsion waves with the spin-flip close to the size of the Compton length muon.

Saturation properties of nuclear matter in the presence of strong magnetic field

Different saturation properties of cold symmetric nuclear matter in the strong magnetic field have been considered. We have seen that for magnetic fields about $B> 3 \times 10 ^ {17}\ G$, {for both cases with and without nucleon anomalous magnetic moments}, the saturation density and saturation energy grow by increasing the magnetic field. It is indicated that the magnetic susceptibility of symmetric nuclear matter becomes negative showing the diamagnetic response especially at $B< 3 \times 10 ^ {17}\ G$. We have found that for the nuclear matter, the magnitude of orbital magnetization reaches the higher values comparing to the spin magnetization. Our results for the incompressibility show that at high enough magnetic fields, i.e. $B> 3 \times 10 ^ {17}\ G$, {the softening of equation of state caused by Landau quantization is overwhelmed by stiffening due to the magnetization of nuclear matter.} We have shown that the effects of strong magnetic field on nuclear matter may affect the constraints on the equation of state of symmetric nuclear matter obtained applying the experimental observable.

Background field approach to electromagnetic properties of baryons

We investigate the self-energies of particles in an external magnetic field $B$. The dependence is generally of the type $\sqrt{P(B)}$ with $P$ a polynomial in $B$ and the participating masses. The non-analytic point depends on the mass and charge constellations, is unproblematic for stable particles but constrains the linear energy shift approximation for resonances. We calculate the $B$ dependent self-energies of the nucleon and $\Delta(1232)$-isobar in the SU(2) covariant chiral perturbation theory and outline a way to obtain finite volume corrections to the nucleon anomalous magnetic moment without using the three point function method. We show that finite volume corrections might explain present discrepancies of lattice QCD and chiral perturbation theory results in the small pion mass region.

Imaging the Transverse (Spin) Structure of Hadrons

Parton distributions in impact parameter space, which are obtained by Fourier transforming GPDs, exhibit a significant deviation from axial symmetry when the target and/or quark are transversely polarized. Connections between this deformation and transverse single-spin asymmetries as well as with quark-gluon correlations are discussed. The sign of transverse deformation of impact parameter dependent parton distribu- tions in a transversely polarized target can be related to the sign of the contribution from that quarkflavor to the nucleon anomalous magnetic moment. Therefore, the signs of the Sivers function for u and d quarks, as well as the signs of quark-gluon correlations embodied in the polarized structure function g2 can be understood in terms of the proton and neutron anomalous magnetic moments.

Transverse (spin) structure of hadrons

Parton distributions in impact parameter space, which are obtained by Fourier transforming GPDs, exhibit a significant deviation from axial symmetry when the target and/or quark are transversely polarized. Connections between this deformation and transverse single-spin asymmetries as well as with quark–gluon correlations are discussed. The sign of transverse deformation of impact parameter dependent parton distributions in a transversely polarized target can be related to the sign of the contribution from that quark flavor to the nucleon anomalous magnetic moment. Therefore, the signs of the Sivers function for u and d quarks, as well as the signs of quark–gluon correlations embodied in the polarized structure function g2 can be understood in terms of the proton and neutron anomalous magnetic moments.

Transverse (Spin) Structure of Hadrons

Parton distributions in impact parameter space, which are obtained by Fourier transforming GPDs, exhibit a significant deviation from axial symmetry when the target and/or quark are transversely polarized. Connections between this deformation and transverse single-spin asymmetries as well as with quark-gluon correlations are discussed. The sign of transverse deformation of impact parameter dependent parton distributions in a transversely polarized target can be related to the sign of the contribution from that quark flavor to the nucleon anomalous magnetic moment. Therefore, the signs of the Sivers function for $u$ and $d$ quarks, as well as the signs of quark-gluon correlations embodied in the polarized structure function $g_2$ can be understood in terms of the proton and neutron anomalous magnetic moments.

Medium effects of magnetic moments of baryons on neutron stars under strong magnetic fields

We investigate medium effects due to density-dependent magnetic moments of baryons on neutron stars under strong magnetic fields. If we allow the variation of anomalous magnetic moments (AMMs) of baryons in dense matter under strong magnetic fields, AMMs of nucleons are enhanced to be larger than those of hyperons. The enhancement naturally affects the chemical potentials of baryons to be large and leads to the increase of a proton fraction. Consequently, it causes the suppression of hyperons, resulting in the stiffness of the equation of state. Under the presumed strong magnetic fields, we evaluate relevant particles' population, the equation of state and the maximum masses of neutron stars by including density-dependent AMMs and compare them with those obtained from AMMs in free space.

NEUTRON SPIN POLARIZATION IN STRONG MAGNETIC FIELDS

The effects of strong magnetic fields on the inner crust of neutron stars are investigated after taking into account the anomalous magnetic moments of nucleons. The energy spectra and wave functions for protons and neutrons in a uniform magnetic field are provided. The particle spin polarizations and the yields of protons and neutrons are calculated in a free Fermi gas model. Obvious spin polarizations occur when B≥1014 G for protons and B≥1017 G for neutrons, respectively. It is shown that the neutron spin polarization depends solely on the magnetic field strength.

Electroweak Nucleon Decays in a Superstrong Magnetic Field

We study the influence of a magnetic field on the electroweak processes of nucleon decay in a degenerate ideal gas of neutrons, protons, and electrons situated in an external superstrong constant and homogeneous magnetic field with effects due to the interaction of nucleon anomalous magnetic moments with the magnetic field taken into account. For different values of the chemical potentials of degenerate fermions, we obtain expressions for probabilities of electroweak processes, which are assumed to be responsible for the chemical equilibrium in the central domain of a neutron star with a frozen superstrong magnetic field. We show that the difference between the neutron decay probabilities in the presence of a magnetic field B ≪ 1017 G and without this field is completely determined by changing the phase volume of electron states. We discuss the process of proton decay into a neutron, positron, and neutrino. This process is energetically allowed only when the interaction of nucleon anomalous magnetic moments with a superstrong magnetic field is taken into account.

Nucleon Instability in a Degenerate Magnetized Nucleon–Electron Gas

In the framework of the model of a degenerate relativistic ideal neutron–proton–electron gas (np+e− gas) in an external superstrong constant and homogeneous magnetic field, we study the effect of the magnetic field on the state of chemical equilibrium of the np+e− gas and on the processes of electronic (β−) and positronic (β+) nucleon decay taking the effects due to the interaction between the nucleon anomalous magnetic moments and the magnetic field into account. For sufficiently large values of the magnetic induction, the proton density in chemical equilibrium must exceed the neutron density. Including the interaction between the nucleon anomalous magnetic moments Mn,p and the magnetic field results in an insignificant reduction of the proton density, but, as in the case Mn,p = 0, the proton density in chemical equilibrium in the presence of the superstrong magnetic field exceeds the neutron density. We show that if the interaction between the nucleon anomalous magnetic moments and the superstrong magnetic field is taken into account, then the positronic decay of a free proton (i.e., a proton not entering the composition of an atomic nucleus) into a neutron, a positron, and a neutrino can become energetically allowed. We discuss the necessary conditions for realizing the phase transition from the nucleon phase to the quark phase of the substance in the central region of a strongly magnetized neutron star.

Axial vector form factor of nucleons in a light-cone diquark model

The nucleon axial vector form factor is investigated in a light-cone quark spectator diquark model, in which Melosh rotations are applied to both the quark and vector diquark. It is found that this model gives a very good description of available experimental data and the results have very little dependence on the parameters of the model. The relation between the nucleon axial constant and the anomalous magnetic moment of nucleons is also discussed.

NUCLEAR MATTER IN INTENSE MAGNETIC FIELD AND WEAK PROCESSES

We study the effect of magnetic field on the dominant neutrino emission processes in neutron stars. The processes are first calculated for the case when the magnetic field does not exceed the critical value to confine electrons to the lowest Landau state. We consider here magnetic fields up to ~1019 Gauss. We find that fields of strength 1015-1016 Gauss have significant effect on the neutronization process, for the direct URCA process the effect of the magnetic field becomes significant only at ~1019 Gauss. In order to estimate the effect we derive the composition of cold nuclear matter at high densities and in beta equilibrium, a situation appropriate for neutron stars. The hadronic interactions are incorporated through the exchange of scalar and vector mesons in the framework of relativistic mean field theory. In addition the effects of anomalous magnetic moments of nucleons are also considered.

The Equation of State of Neutron Star Matter in Strong Magnetic Fields

We study the effects of very strong magnetic fields on the equation of state (EOS) in multicomponent, interacting matter by developing a covariant description for the inclusion of the anomalous magnetic moments of nucleons. For the description of neutron star matter, we employ a field-theoretical approach, which permits the study of several models that differ in their behavior at high density. Effects of Landau quantization in ultrastrong magnetic fields (B > 1014 G) lead to a reduction in the electron chemical potential and a substantial increase in the proton fraction. We find the generic result for B > 1018 G that the softening of the EOS caused by Landau quantization is overwhelmed by stiffening due to the incorporation of the anomalous magnetic moments of the nucleons. In addition, the neutrons become completely spin polarized. The inclusion of ultrastrong magnetic fields leads to a dramatic increase in the proton fraction, with consequences for the direct Urca process and neutron star cooling. The magnetization of the matter never appears to become very large, as the value of |H/B| never deviates from unity by more than a few percent. Our findings have implications for the structure of neutron stars in the presence of large frozen-in magnetic fields.

Aspects of chiral pion-nucleon physics

The next-to-leading order chiral pion-nucleon Lagrangian contains seven finite low-energy constants. Two can be fixed from the nucleon anomalous magnetic moments and another one from the quark mass contribution to the neutron-proton mass splitting. We find a set of nine observables, which to one-loop order only depend on the remaining four dimension-two couplings. These are then determined from a best fit. We also show that their values can be understood in terms of resonance exchange related to Δ excitation as well as vector and scalar meson exchange. In particular, we discuss the role of the fictitious scalar-isoscalar meson. We also investigate the chiral expansion of the two P-wave scattering volumes P 1 − and P 2 + as well as the isovector S-wave effective range parameter b −. The one-loop calculation is in good agreement with the data. The difference P 1 − − P 2 + signals chiral loop effects in the πN P-waves. The calculated D- and F-wave threshold parameters compare well with the empirical values.

Prediction of the anomalous magnetic moment of the nucleon from the nucleon anomaly

We construct the effective anomaly lagrangian involving nucleons and photons by using the current-current coupling method. The contribution of this lagrangian to the anomalous magnetic moment of nucleon is purely isovector. The anomalous magnetic moment of the proton, κ P , can be calculated from this lagrangian and it is found to be κ P Theor. = 1.77, which is in excellent agreement with the experimental value κ P Exp. = 1.79. While for the neutron, κ N Theor. = −2.58 as compared to κ N Exp. = −1.91, is less satisfactory, but the sign is correct.

Perturbative QCD analysis of exclusive pair production of higher-generation nucleons.

Results are presented of a perturbative QCD analysis of heavy-baryon form factors to leading order in ${\ensuremath{\alpha}}_{s}$ including all higher-twist quark-mass effects. A dip in the total cross section for the ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$ pair production of some higher-generation nucleons is predicted. The results are consistent with the definition of charge form factors at zero momentum transfer and reproduce the well-known anomalous magnetic moments of nucleons. These considerations resolve a sign ambiguity in previous leading-twist analyses of the hard-scattering contribution to the proton magnetic form factor.

The nucleon anomalous magnetic moment and meson exchange current operators

Abstract The anomalous magnetic moment term in the nucleon electromagnetic current operator leads to an important correction to the pion and ϱ -meson exchange current operators. The additional term is essential for quantitative predictions of the backward deuteron electrodisintegration cross section and the magnetic form factors of the trinucleons.

Strong-coupling expansion with fermions: The formalism and an application

We review and discuss some properties of the strong-coupling expansion for a single scalar field with a quartic self-interaction. We generalize the method to the case of fermions and mesons, called, maybe unduly, nucleons and pions, interacting through a Yukawa coupling, and propose a renormalization program. We apply the ideas and the techniques to a leading-order calculation of the nucleon anomalous magnetic moments, with the result ${\ensuremath{\mu}}_{p}=\ensuremath{-}{\ensuremath{\mu}}_{n}=2.33$.