One-gluon exchange corrections to magnetic moments of baryons

One-gluon exchange (OGE) corrections to the magnetic moments of the octet baryons are studied in the bag model. It is clarified that OGE resolves a problem of μ(Λ) and μ(Ξ^?) in previous quark model calculations and also improves an overall agreement between theory and experiment.     

Multiquark picture for Σ (1620)

In this work we report on a new QCD sum rule analysis to predict masses of the excited baryon states (e.g. Σ (1620) and Λ (1405)) by using multiquark interpolating fields ((qˉq)(qqq)). For the Σ (1620) we consider the ˉKN, πΣ, and πΛ (I = 1) multiquark interpolating fields. The calculated mass from those multiquark states is about 1.592 GeV. For the Λ (1405) we first show the result using the π⁺Σ⁻+π⁰Σ⁰+π⁻Σ⁺ (I = 0) multiquark interpolating field, and compare the calculated mass to that of our previous result using the π⁰Σ⁰ multiquark state. We then show that the mass 1.405 GeV is well reproduced when using the ˉKN (I = 0) multiquark state. The uncertainties in our sum rules are also discussed. Received: 7 September 1998 / Revised version: 5 January 2000     

Spectra of charmed and bottom baryons with hyperfine interaction

Up to now,the excited charmed and bottom baryon states have still not been well studied experimentally or theoretically.In this paper,we predict the mass of ?*b,the only L=0 baryon state which has not been observed,to be 6069.2 Me V.The spectra of charmed and bottom baryons with the orbital angular momentum L = 1 are studied in two popular constituent quark models,the Goldstone boson exchange(GBE) model and the one gluon exchange(OGE) hyperfine interaction model.Inserting the latest experimental data from the "Review of Particle Physics",we find that in the GBE model,there exist some multiplets(Σc(b),Ξ c(b)and ?c(b)) in which the total spin of the three quarks in their lowest energy states is 3/2,but in the OGE model there is no such phenomenon.This is the most important difference between the GBE and OGE models.These results can be tested in the near future.We suggest more efforts to study the excited charmed and bottom baryons both theoretically and experimentally,not only for the abundance of baryon spectra,but also for determining which hyperfine interaction model best describes nature.     

Über eine Näherung für Gitterelektronen in äußeren Feldern

The Hamilton operator of an electron in a periodic lattice potential under influence of external electric and magnetic fields with potentialsV(r) andA(r) resp. is often replaced by an approximate operatorW ⁰ (?i?+A(r))+V(r) for one single energy bandW ⁰(k) which means a renormalization of the kinetic energy by the lattice. The validity of this replacement is examined and the magnitude of its error is roughly estimated. Neglecting other bands one obtains an error term proportional to the derivative of the electric field strengthF, if one takes a suitable position of the “raster” of the replacement operator, and to the square of the magnetic field strengthB resp. The decoupling from the other energy bands leads to error terms proportionalF ² andB ² resp. which however in the general case increase rapidly in the vicinity of overlapping energy bands.     

Scalar Charged Particle in Presence of Magnetic and Aharonov–Bohm Fields Plus Scalar–Vector Killingbeck Potentials

The generalized form of Killingbeck potential is an attractive Coulomb term plus a linear term and a harmonic oscillator term, i.e. ?a/r + br + λr ², which has a useful application in quarkonium spectroscopy. The ground state energy with the corresponding wave function are obtained for any arbitrary m-state in two-dimensional Klein–Gordon equation with equal mixture of scalar–vector Killingbeck potentials in the presence of constant magnetic and singular Ahoronov–Bohm flux fields perpendicular to the plane where the interacting charged particle is confined. The analytical exact iteration method is used in our solution. We obtain the energy eigensolutions for particle and antiparticle corresponding to S(r) = V(r) and S(r) = ?V(r) cases, respectively. Some special cases like the Coulomb, harmonic oscillator potentials and the nonrelativistic limits are found in presence and absence of external fields.     

Proton-irradiated Pb(Zr0.52Ti0.48)O3 thick films for flexible non-volatile memory applications

We investigated the ferroelectricity in proton-irradiated flexible Pb(Zr_0.52Ti_0.48)O₃ (PZT) thick films and their non-volatile memory characteristics. The Ni-Cr metal foil substrate allowed high-quality polycrystalline PZT films with flexible functionality to be fabricated using conventional sol-gel and high-temperature annealing methods. The 10-MeV proton-irradiated PZT film exhibited an almost square polarization?electric field hysteresis curve with saturated (P_s) and remnant (P_r) polarizations of 18.9 and 17.0 μC/cm², respectively; which are slightly lower than as-grown PZT with P_s = 28.7 μC/cm² and P_r = 24.3 μC/cm². The P_r did not decrease even after 1000 cycles of continuous bending and unbending at a bending radius of 2.14 mm and decreased slightly to ～80% of its initial value after 10⁵ s. Although the P_r decreased to ～55% after 10¹⁰ cycles, the electric polarization remained switchable under positive and negative electric fields. These characteristics suggest that the flexible PZT films could be utilized in non-volatile memory device applications in environments with high doses of proton irradiation, such as those in aeronautics and nuclear power plants.     

A modified born term model for π± Δ electroproduction

An electric Born type model is used to describeπ ^± Δ electroproduction at high energies. The electric pion form factor is taken from VDM; the contact term form factor and theΔ form factor are set equal to the proton form factor (or equal to zero) which is left as an arbitrary parameter, and is determined by a fit of the model to the recentπ ⁺ δ ⁰ andπ ^? Δ ⁺⁺ electroproduction data.     

Long Range Potential Component in the NN Force

The Fourier transform of the Born term of the AGS equation in the NNπ-system generates an energy-dependent Yukawa-type local NN-quasi-potential. An appropriate average with respect to energy suggests a variety of local NN-potentials with different ranges: 1/r(r + a) ^m?1 (for 2 ≤ m) where in the long range region it becomes 1/r ^m , while in the short range region the Yukawa-type potential e ^?(m?1)r/a /r results. Therefore, one finds that the Yukawa potential is automatically accompanied by an additional longer range interaction 1/r ^m . For m = 2, the potential 1/r ² produces Efimov-like bound states in the deuteron spectra. The m = 6, 7 cases lead to the Van der Waals potential.     

Long-range potentials and the electromagnetic polarizabilities

The long-range spin and velocity independent forces of electromagnetic origin which act between any two systems are studied for those cases in which no forces of this type exist to order e². It is shown that they are uniquely determined by the charge, magnetic moment, and polarizabilities of both systems, not only to the dominant order r^?n, but also to the next one r^?(n+1). These potentials provide the link between Compton scattering polarizabilities (response to real photons) and classically defined polarizabilities (response to static electromagnetic field). The two definitions are shown to be equivalent for neutral spinless systems; the problems arising for a neutral particle with magnetic moment are studied in detail. The r^?(n+1) terms have no classical counterpart, since they are due to the relativistic quantum propagation of the system which carries charge or magnetic moment. The results are of general validity with analyticity, crossing, unitarity, and gauge invariance as only inputs. The most general conclusion is that the polarizabilities represent electromagnetic properties of a system at order e², as the charge and magnetic moment do at order e. Thus they give the strength of the response to electric and magnetic fields, independently of the specific characteristics of the electromagnetic agent.     

Gaussian approximations for the nuclear Coulomb interaction

The kernel 1/¦r-r′¦=1/y in the direct term of the average Coulomb potential of the nuclear Hartree-Fock model is approximated by a sum of gaussians iny. For 0.5≦y≦30 Fm, a sixteen term expression is found such the direct Coulomb energy is obtained to one part in 10³. The exchange Coulomb potential is estimated in the statistical model. Applications of these accurate and practical approximations to fission calculations are discussed.     

Isotope shifts and hyperfine splitting in HfI changes in nuclear charge radii of stable isotopes and182Hf

Isotope shifts and hyperfine structures in three optical transitions of HfI are investigated. Magnetic dipole coupling constant A and electric quadrupole coupling constant B of four atomic levels for both stable odd-even isotopes¹⁷⁷Hf and¹⁷⁹Hf are determined. Nuclear charge radii changesδ〈r ²〉 of the stable Hf isotopes and¹⁸² Hf (T _1/2=9×10⁶ y) are extracted using the standard semiempirical procedure. Strong deviation from muonic atom data onδ〈r ²〉 is observed. The course of theδ〈r ²〉 dependence on mass number indicates changes in nuclear deformation at A=174 and influence of higher order deformations on nuclear shape in this region.     

Electric field properties at cationic sites in normal, incommensurate and commensurate K2ZnCl4 crystals

The local electric properties at K and Zn sites in the normal, incommensurate and commensurate phases of K₂ZnCl₄, as derived from a numerical computation of the lattice contributions to the electric potential V(r), electric field intensityE(r) and electric field gradient tensorV _αβ(r) are reported. The numerical data obtained at each cationic position were correlated with the experimental³⁹K NMR, Cu²⁺ and Mn²⁺ EPR and⁵⁷Fe Mössbauer results in pure and doped K₂ZnCl₄. A proportionality between crystal field and zero-field splitting was taken into account for Mn²⁺, whereas for K⁺, Cu²⁺ and Fe³⁺ ions the electric field gradient is directly related to the crystal field parameter. By this comparison, on computations done in the ionic fractional charge and relaxed lattice approximations, the insertion of probe-species of iron, copper and manganese ions on off-center Zn sites is proposed. The³⁹K electric field gradient tensor calculations in the incommensurate phase fit well with the NMR data reported recently.     

On the theory of the resonant interaction of electrons with a high-frequency electric field in one-dimensional two-barrier nanostructures with symmetric barriers of finite height and width

The theory of the interaction of electrons with a high-frequency electric field in one-dimensional two-barrier nanostructures with symmetric barriers of finite height and widths was developed. An exact solution to the Schrödinger equation was found for electrons in this nanostructure in the absence of high-frequency electric field. An analytical expression for the direct current I ₀ induced in this structure by an incident electron flux with energy ε differing slightly from the resonant level energy ε _r (|ε ? ε _r | << ε _r ) was derived. In the small-signal approximation, the active (field-phased) component I _c of the alternating electric current was calculated. At ε > ε _r , the current I _c is negative in the entire frequency range, which suggests the possibility of ac electric field amplification and generation in the two-barrier resonant-tunneling structure with the barriers of finite height and width. Within the applicability of the theory (?ω << ε _r ), the frequency at which amplification and generation of the ac electric field are possible reaches ω ? 10¹³ s ^?1; the power transferred by electrons to the field is ～1 W/cm².     

Lattice energy of alkali halide crystals

A new repulsive term in the ionic interaction potential ψ(r) = Ar^?ne^?r/gl, is suggested and the three unknown parameters A, λ and n are evaluated. Lattice energies of alkali halide crystals are calculated using this form. The results agree fairly well with the experimental values.     

Granular electrostatics: Progress and outstanding questions

Every physicist studies electrostatics in the first year of graduate study, and learns that the electric field is a linear superposition of contributions from charges, each of which obeys a 1/r ² law. Every physicist also studies classical mechanics, and learns that the problem of three or more bodies in a 1/r ² field is intrinsically nonlinear. The contradiction between these two teachings is seldom commented upon. In this paper, I overview what is known, what is believed, and what remains entirely unknown about the behaviors of multiple electrically polarized or charged particles. I show that the nonlinearity recognized in classical mechanics leads to highly complex dynamics when particles are permitted to act in the presence of electric fields. I describe several simple problems that lead to effects that are not understood in any way, and I conclude with the proposition that what we know and believe are insignificant compared with the effects that we know to exist but cannot explain.     

Universility of hadron jets in soft and hard particle interactions at high energies

Hadron jet production is studied in softπ ^? p and cumulativeπ ^? C interactions at a 40 GeV/c momentum. The collective characteristics of jets and the form of the quark and diquark fragmentation into charted poins and neutral strange particles are analyzed. The results obtained are compared to analogous data fore ⁺ e ^? andv(≈v)p interactions. The hadron jet properties are also studied by means of relativistic invariant variables—the squared relative 4-velocities \(b_{ik} = - \left( {\frac{{P_i }}{{m_i }} - \frac{{P_k }}{{m_k }}} \right)^2 \) . The results obtained show that quark (diquark) fragmentation proceeds in a similar manner in soft hadron-hadron collisions, cumulative interactions on light nuclei,e ⁺ e ^? annihilation and deep inelasticv(≈v)p scattering. In the relativistically invariant variables the fragmentation function is similar for the hadronization of quarks and diquarks and it does not matter whether they are knocked out of usual hadrons or multiquark systems.     

Λ(1405) as a multiquark state

In the QCD sum rule approach we predict the Λ (1405) mass by choosing the π⁰Σ⁰ multiquark interpolating field. It is found that the mass is about 1.419 GeV from Π₁ (q ²) sum rule which is more reliable than Π_q (q ²) sum rule, where Π_q (q ²) and Π₁ (q ²) are two invariant functions of the correlator Π (q ²). We also present the sum rules for the K ⁺ p and the π⁺Σ⁺ multiquark states, and compare to those for the π⁰Σ⁰ multiquark state. The mass of the Λ (1600) can be also reproduced in our approach. Received: 11 November 1997 / Revised version: 28 April 1998     

A theorem on electromagnetic properties of leptons

The following theorem is proven: Every lepton with the mass m, electric charge q and spin J belonging to any representation of a non-abelian gauge group must have the magnetic moment μ = qJm^?1, electric mean squared radius r² = qJ(J + 1)m^?2 and electric quadrupole moment Q = qJ(2J ? 1)m^?2 in the first order of the electromagnetic effects in an arbitrary renormalizable theory with the non-abelian gauge group symmetry which permits the validity of the Gerasimow-Drell-Hearn and Cabibbo-Radicati sum rules. The formula for the magnetic moment applies also for an abelian symmetry and remains valid even if the gauge symmetry is spontaneously broken.     

Searching for Exotic States with b and c Quarks in D0 Experiment

The latest results of searching for exotic multiquark states with heavy quarks obtained in the D0 experiment (Fermi National Accelerator Laboratory, USA) are presented. In particular, the evidence of existence of a possible four-quark state X(5568) → B _s ⁰ π^±in the cases with hadronic and semileptonic decay channels of B _s ⁰ meson is considered, as well as the results of searching for the five-quark states in the J/ψΛ system.