Neutrino self-energy operator and neutrino magnetic moment

A simple method for calculating the magnetic moment of a massive neutrino on the basis of its self-energy operator is presented. An expression for the magnetic moment of a massive neutrino in an external electromagnetic field is obtained in the R _ξ gauge for the case of an arbitrary ratio of the lepton and W-boson masses.     

Mesonic degrees of freedom in nuclei and the definition of meson-exchange currents

We describe the nucleus by a meson-nucleon system. Starting from a covariant field theoretical Hamiltonian we derive an effective Schrödinger equation for the nucleonic components. The meson-exchange currents are then defined unarbitrarily by an effective operator (current) in the space of the nucleonic components. The advantage over theS-matrix method [1] is discussed. In the nonrelativistic limit the meson-current as well as the seagull (pair) current agrees with theS-matrix result. Recoil and wavefunction orthogonalization cancels completely in this limit.     

Mesonic degrees of freedom in nuclei and retardation effects in meson-exchange currents

In the present paper we give a brief review of a consistent calculation of meson-exchange effects. For the charge density these currents are calculated up to the order of $\text{O(}\text{1}\text{M}{}^3\text{)}$ for π, ρ- and ω-exchange. The retardation currents arising from the recoil and wave function reorthonormalization currents are derived. A quantitative discussion of the retardation currents is done for the example of the deuteron form factors. As for the quadrupole form factor the retardation contribution is shown to be important. In the case of the charge form factor these effects are unimportant for our choice of deuteron wave functions.     

Low energy orbital magnetic dipole excitations of heavy nonspherical nuclei

To clarify the physical nature of the orbital magnetic dipole excitations discussed widely in the past few years, a semiclassical model is presented and the nuclei¹⁵⁶Gd and¹⁶⁴Dy are investigated microscopically. The semi-classical model involves a consistent treatment of vibrational and rotational degrees of freedom; the microscopic results are obtained in quasiparticle-random-phase approximation (QRPA) with a realistic effective interaction. The results disagree with the picture of scissors modes or rotational vibrations.Dedicated to Prof. Dr. H.J. Mang on the occasion of his 60th birthday     

The magnetic moment of the proton

In this paper the author calculates the magnetic moment of a bare proton in a non-relativistic approximation on the condition that the proton is a particle which is capable of existing not only in a state with spin 1/2but also in a state with spin 3/2.     

The magnetic moment of103Ru

The nuclear magnetic moment of¹⁰³Ru has been determined using the technique of low-temperature nuclear orientation on¹⁰³Ru as a dilute impurity in Fe. The Fe lattice was cooled to 1.7 mK using a PrNi₅ enhanced nuclear demagnetisation stage precooled with a³He–⁴He dilution refrigerator. The¹⁰³RuFe system was observed to have a long nuclear spin-lattice relaxation time, but analysis of the relaxation indicates that the¹⁰³Ru nuclei are close to thermal equilibrium with the Fe lattice at times>200 min after demagnetising. From the near thermal equilibrium anisotropy of the 497 keV -ray in¹⁰³Rh we have deduced the nuclear magnetic moment as |(¹⁰³Ru)|=0.18(2)_N. This value is almost independent of the choice of spinI=3/2 or 5/2 for the nucleus, but is only consistent with systematics ifI(¹⁰³Ru)=3/2 and <0. UsingI=3/2 we obtain the E2/M1 mixing ratio of the 497 keV -ray as =–0.42(4). The sign of the anisotropy of the 610 keV -ray from the 650 keV level in¹⁰³Rh is only consistent with an allowed -decay to the state ifI(650 keV,¹⁰³Rh)=5/2. The E2/M1 mixing ratio of the 610 keV -ray is then =+0.15(3) or +60( _–40 ⁺ ), <–80. From the initial rise in -ray anisotropy following demagnetisation we determine the Korringa constant for¹⁰³RuFe to beC=5.7(5) K·s.     

The magnetic moment of the antiproton

A scheme is proposed with which it may be possible to utilize extremely cold antiprotons in a Penning trap to measure the magnetic moment of an antiproton.     

The evolution of the magnetic moment in a corrugated magnetic field

In the first part, the equations of motion in a weakly corrugated, periodic magnetic field are linearized and solved by using paraxial approximation, to describe the model and the associated resonance condition. In the second part, the nonlinear evolution of the magnetic moment of resonant particles, in connection with their axial displacement is investigated analytically by using the multiple scale method. It is seen that the linear evolution is converted into a slow and periodic oscillation around the unperturbed value, with a considerable amplitude. The analytic expressions for the period and amplitude of the oscillations are derived and compared with the numerical simulations, which are also presented. Finally, the limitations of the paraxial approximation are concluded by investigating the numerical simulations, with actual field expressions. (c) 1997 American Institute of Physics.     

Alpha-clustering effects in heavy nuclei

The study of cluster structures in light nuclei is extending to the heavy nuclei in these years. As for the stable N = Z nuclei, from the lighter ⁸Be, ¹²C nuclei to the heavier ²⁰Ne and even the ⁴⁰Ca and ⁴⁴Ti medium nuclei, the α cluster structures have been well studied and confirmed. In heavy nuclei, due to the dominated mean field, the existence of α cluster structure is not clear as light nuclei but some clues were found for indicating the core+α cluster structure in some nuclei, in particular, the ²⁰⁸Pb+α structure in ²¹²Po. We review some recent progress about the theoretical and experimental explorations of the α-clustering effects in heavy nuclei. We also discuss the possible α cluster structure of heavy nuclei from the view of α decay.     

The Galilean and translationally invariant operator algebra describing nuclei

The Galilean and translationally invariant field operator formalism developed in the parts I and II is applied to the shell model with harmonic potential. In spite of the complicate structure of the commutation relations some essential analogies to the non-invariant calculus can be verified. The unperturbed ground state can be described as quasi-vacuum. Further the one-particle density is diagonal in the energy representation. This fact admits the invariant use of the concepts of “occupied” and “unoccupied” states, in a somewhat modified, but well-defined sense.     

The Galilean and translationally invariant operator algebra describing nuclei

The deviation of the commutation relations of the Galilean and translationally invariant field operators (given in part I) from the exact Fermi commutation relations is investigated. For this purpose the invariant field operators are integrated with one-particle functions describing a compactn-particle system of nucleons and its low excitations. With this assumption an approximate expression for the (subtractive) deviation of both commutation rules from one another is given. It is carefully estimated that the exact deviation, taken in the operator norm, is of ordern ^?2/3. It is shown that the degree of compactness of nuclear matter in the phase space plays an essential role in the determination of this estimate.     

Isomeric states in heavy nuclei

The one- and two-quasiparticle states in heavy nuclei are treated. The change of one-quasiparticle states in isotone chain seems to be rather smooth. Two-quasiparticle states in nuclei of alpha-decay chain of ²⁷⁰Ds are discussed.     

The anomalous magnetic moment of the electron

The value of the electron's magnetic moment is a fundamental quantity in physics. Its deviation from the value expected from Dirac theory has given enormous impetus to the field of quantum theory and especially to quantum electrodynamics (QED) as the relativistic quantum field theory of electrodynamics. In fact, the measured values both for free and for bound electrons are explained by corresponding QED calculations on the part per trillion and part per billion level of accuracy, respectively. This agreement is amongst the best known in physics today. In turn, it allows highly precise determinations of related fundamental constants like the fine structure constant α or the electron mass. The present article discusses the application of the continuous Stern–Gerlach effect to the precise measurement of magnetic moments, especially of the electron bound in highly charged ions and possible tests of calculations in the framework of QED of bound states. Also, a test of QED in a more general approach by the comparison of values for the fine structure constant derived from different measurements, will be discussed.     

The electron magnetic moment at high temperature

The one-loop QED correction to the electron magnetic moment is computed at high temperature. We find that the correction reduces the magnetic moment.     

The muon magnetic moment and new physics

The impact of the muon magnetic moment measurement on physics beyond the Standard Model is briefly reviewed. Particular emphasis is given on the case of supersymmetry. The sensitivity of g ? 2 to supersymmetry parameters and the potential for model discrimination and parameter measurements is described. The interplay between LHC data on the Higgs boson, limits on new particles, and g ? 2 is discussed.