S = −1 dibaryon formation in the ∑−D atom

An estimate of the formation rate of the strangeness S = −1 dibaryons D_s and D_t via “∑⁻-capture” in a ∑⁻d atom is presented. Reasonable branching ratios are expected for formation from the atomic P orbitals. The ∑⁻d atom experiment is found to be sensitive to the formation of D_s dibaryons in a mass range of only 10 MeV starting at the ∑⁻p mass, while for the D_t dibaryons in a range of 30 MeV is expected.     

Investigation of the diffractive reaction p + N → [∑+ K 0] + N at the proton energy of E p =70 GeV and observation of the decay process X(2000) → ∑+ K 0

The diffractive reaction p + N → [∑⁺ K ⁰] + N induced by 70-GeV protons is investigated at the SPHINX facility. The measured mass spectrum of the ∑⁺ K ⁰ system originating from this reaction shows a resonance structure with a mass of M=1995±18 MeV and a width of Γ=90±32 MeV. The cross section for the formation of this structure is found to be σ=182±38 nb per target nucleon. These data comply well with the results that we obtained previously in studying the reaction p + N → [∑⁰ K ⁺] + N, where we observed the formation of the X(2000) → ∑⁰ K ⁺ state, a candidate for an exotic baryon with hidden strangeness. The measured ratio R of the two branching fractions, R = Br[X(2000) → ∑⁺ K ⁰]/Br[X(2000) → ∑⁰ K ⁺] = 1.91 ± 0.38, is consistent with the value of R=2 expected for an isospin-1/2 baryon.     

Measurement of isotope shifts,fine and hyperfine structure splittings of the lithium D lines

The lithium D lines were studied using a diode laser that was frequency modulated by an electro-optic modulator, to excite an atomic beam. The transmission of part of the laser beam through an etalon was monitored to correct for the nonlinearity of the laser scan. The results for the ^6,7Li 2 S _1/2 and 2 P _1/2 hyperfine splittings agree very well with the best existing data while those for the D1 isotope shift and ^6,7Li fine structure splittings disagree significantly from data obtained by a previous laser atomic beam experiment. Our result for the D1 isotope shift is very close to the latest value computed using Hylleraas variational theory. Received 8 April 2002 / Received in final form 26 June 2002 Published online 21 January 2003 RID="a" ID="a"e-mail: wvw@yorku.ca     

Mass splitting in supersymmetric theories from an effective lagrangian point of view

Gauge and global internal symmetries, even when spontaneously broken, restrict the possible mass splittings within supermultiplets. A systematic method of analysis is presented which is applicable both for 〈F〉- and 〈D〉-type supersymmetry breaking, with emphasis on avoiding unacceptable splittings within the quark and lepton supermultiplets. Expressions for gluino and photino masses are also obtained.     

Strong and electromagnetic mass splittings in heavy mesons

The contributions to heavy meson mass differences by the strong hyperfine interaction, the light quark masses and the electromagnetic interaction are obtained from the empirical values of the D  , D^∗$D^{\ast }$, B   and B^∗$B^{\ast }$ masses by means of a mass formula based on the heavy quark mass expansion. The three different types of contributions are determined with significant accuracy to next to leading order in that expansion.     

Electromagnetic corrections to masses and widths in the baryon decuplet,and to π± d cross section at the Δ resonance

The electromagnetic mass splittings of theΔ andγ members of the decuplet are estimated and the resulting decay widths are calculated, assumingSU(2)-invariance of the coupling constants for “unmixed” states. Three additional Coulomb corrections occur when deuterons are used as neutron targets. The combined effects onπ ^± d total cross sections are given.     

Electromagnetic mass splittings of heavier hadrons in quantum chromodynamics

The electromagnetic mass splittings of heavier hadrons are estimated in the framework of gauge theory model where ligher quarks are taken to behave relativistically and the spatial wave functions are described by the spin-spin interaction affected relative distances between quarks. The predictions for (Ξ⁻-Ξ⁰), (Σ*⁰−Σ*⁺), (Ξ^*−-Ξ^*0), (D _c ⁺−D _c ⁰) and (D _c ^*+ −D _c ^*0 ) are in fair agreement with the experimental data available whereas those for (D _b ⁻ −D _b ⁰ ) and (D _b ^*− −D _b ^*0 ) are in qualitative agreement with other theoretical estimates.     

A Quark Model for Baryon Production at Low Transverse Momentum

A quark model for baryon production at low p_T is obtained as generalization of the quark-antiquark fusion model. The quark transverse momenta are taken into account using an average transverse mass of the quarks. This leads to the incorporation of both quark fusion and quark recombination into one model. The model is able to describe qualitative features of the reactions pp → (Δ, ¯Δ, ∑⁺, ∑^?) + X at 12 and 24 GeV/c.     

Crystal field and exchange interactions in the SmFe3(BO3)4 multiferroic

The optical spectra of oriented SmFe₃(BO₃)₄ single crystals are studied in the region of the f-f transitions in the Sm³⁺ ion by Fourier spectroscopy. The energies, the symmetry properties, and the exchange splittings of the Stark sublevels of the ground and 17 excited multiplets of the Sm³⁺ ion in a crystal field of symmetry D ₃ are determined from the measured temperature dependences of polarized-radiation absorption spectra. The parameters of the crystal field acting on samarium ions and the parameters of the exchange interaction between Sm³⁺ and Fe³⁺ ions are found. The anisotropy of the effective exchange interaction is shown to be substantially stronger than the magnetic anisotropy, due to a strong crystal-field-induced mixing of the ground and excited multiplets.     

ESR study of Fe3+ and Mn2+ ions on trigonal sites in ilmenite structure MgTiO3

Electron spin resonance has been observed for Fe³⁺ and Mn²⁺ ions occupying sites with trigonal symmetry in undoped and doped Verneuil-grown crystals of the ilmenite type compound MgTiO₃. At 300 K, the fine structure parameters in the spin Hamiltonian are (in 10^?4cm^?1) D = +844 (± 1), (a? F) = +118 (± 1), a = 69 (± 7) for Fe³⁺ and D = +164 (± 1), (a ? F) = +10.2 (± l), a = 7.0 (± 1) for Mn²⁺. These values are compared with literature data for Fe³⁺ and Mn²⁺ in other oxides, especially Al₂o₃, with particular reference to the recent “superposition” theory of the effect of a trigonal distortion. From the orientation of the axes of cubic pseudosymmetry of the spin Hamiltonian, and with the assumption that a has the same sign for both ions, it is proposed that Fe³⁺ and Mn²⁺ occupy the same octahedral site, namely the Mg²⁺ site. Anomalous line splittings observed for one sample were attributed to twinning on (0001) or {1120} planes.     

Photon-echo detected nuclear quadrupole resonance spectroscopy

Rare-earth-ion-doped crystals (REICs) have played an important role in quantum information processing due to their excellent coherent properties. In order to obtain the information regarding the hyperfine structures of the rare-earth ions in REICs, optically detected nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) techniques based on RF resonance and various optical detection methods are widely employed in previous works. Here we demonstrate a new method of NQR spectroscopy based on the photon-echo detection. The hyperfine spectra of the ground state (⁷F₀) and the optically-excited state (⁵D₀) of ¹⁵¹Eu³⁺ in Y₂SiO₅ at zero field are obtained. This method can determine the hyperfine splittings within the ground state and the optically-excited state and is shown to be robust against electrical noise. Our results provide an alternative way for optical detection of NMR and NQR with high signal-to-noise ratio.     

Spin-orbit coupling in oxygen near the dissociation limit

By using the method of configuration interactions in the valence basis with triple exponentials, the spectrum of the oxygen molecule is calculated in a range of internuclear distances from 1.2 to 2.45 Å, with the matrix of configuration interactions being diagonalized with regard to the spin-orbit coupling. The matrix elements of the spin-orbit coupling are presented, along with the spin splittings of triplet and quintet states. Particular attention is given to the intermediate range for the breaking of the O=O bond (1.8–2.45 Å), where the strong mixing of multiplets and rearrangement of the valence bonding to the atomic limit O(³ P)+O(³ P) occur. Other dissociation limits up to O(¹ D)+O(¹ D) are also taken into account. The results obtained are discussed in the context of the theory of the chemical bond, catalysis, radiation collisions, and the theory of spectral bands for high vibrational quantum numbers.     

Baryon mass splitting by the strong hyperfine interaction and SU(3) breaking

We calculate mass splittings of strange and non-strange baryons in the [56, 0⁺] and the [70, 1^?]. As the most important spin-dependent force we only analyse the hyperfine interaction. The exact treatment of the quark mass breaking shows contributions which have not been considered in similar investigations up to now. Taking $\text{mλ}\text{m}{}_{\mathrm{<mtext>p</mtext>}}\text{? 2}$ and popular values for the slope of the linear potential a, the strong coupling constant α_s and the p-quark mass, we get excellent results for the four mass splittings 〈Σ-Λ〉, $\text{〈Σ}{}^1\text{? Σ〉}$, 〈Δ-N〉 and $\text{〈Ξ}{}^1\text{? Ξ〉}$ in the [56, 0⁺]. The structure of mass spectrum in the [70, 1^?] is well described, too; the strong SU(3) mixing of Σ and Λ states is seen to be due to the quark mass breaking. Predictions for missing Σ states in the [70, 1^?] as as for splittings between charmed baryons can be made.     

Determination of odd-symmetry crystal-field parameters from optical spectra

We have obtained analytical expressions for effective parameters of the crystal field that acts on spin-orbit multiplets of 4f ^N configurations taking into account admixture to them of 4f ^N?15d excited states and ligand-to-metal charge-transfer states. As an example, we analyze splittings of the ground and excited multiplets of Pr³⁺ and Tm²⁺ ions in some crystals without an inversion center. The effect of mixing of states of different configurations is most strongly pronounced for the ¹ G ₄ and ¹ D ₂ excited multiplets. The interconfigurational contribution to splittings is different for different multiplets. This circumstance makes it possible to estimate the values of the parameters of the odd-symmetry crystal field, which causes mixing of the 4f ^N and 4f ^N?15d states, and the covalence parameters of rare-earth ion-ligand bonds.     

Next-nearest neighbour effects in the Mössbauer spectra of Cr-spinels: An application of partial quadrupole splittings

Mössbauer spectra of Fe(Cr, Al)₂O₄ spinels are reported and interpreted using partial quadrupole splitting theory. Fe²⁺T site quadrupole splittings are calculated for different next-nearest neighbour configurations. Assuming random distribution of the Cr³⁺ and Al³⁺ in the octahedral M sites, good semiquantitative agreement between calculated and observed quadrupole splittings and absorption intensities is obtained.     

Are spin-dependent forces in charmonium generated through scalar-vector admixture?

I show that if the spin-dependent confining forces are generated through scalar-vector admixture then the ³p_J splittings restrict the vector to scalar ratio to be less than half. Further it is shown that an accurate measurement of the ¹p₁ mass can clearly distinguish this model from vector and scalar exchange models.     

Electronic structure and spectrum of Cr3+ in LiCaAlF6

The electronic structure and spectrum of Cr³⁺ in LiCaAlF₆ are investigated by using the discrete variatitional-local density functional (DV-LDF) method with embedded cluster model. The clusters (CrF₆)^3– withC ₃,D _3d andO _h point group symmetries embedded in the crystal are treated. The one-electron energy levels, densities of states, orbital populations, spin polarization splittings and energies of some terms are calculated. The results show that the relaxation of F^– ions around the Cr³⁺ impurity is inevitable, and that theD _3d andO _h (CrF₆)^3– clusters, with an extended bond-lengthR(Cr–F) chosen to be equal to 1.88 Å can represent this relaxation in a much better way. All the ligand-field transition energies, which are obtained from the transition-state energy and the Griffith parameters, as yielded by a restricted one-electron DV-LDF calculation, compare well with the experimental ones.     

Isotope effects in the EPR spectrum of a tin-vacancy pair in silicon

The S = 1 EPR spectrum for a tin-vacancy pair in silicon reveals easily detected isotope shifts in the fine structure splitting D for the various nuclear isotopes of tin (σD/D = + 1.0 × 10^?4 per unit mass) as well as well as those for the six near neighbor silicon atoms (σD/D = ?0.67 × 10^?4 per unit mass). These are attributed to the different vibrational amplitudes vs isotopic mass.     

Riccion from higher-dimensional space-time with D-dimensional sphere as a compact manifold and one-loop renormalization

Lagrangian density of riccions is obtained with the quartic self-interacting potential using higher-derivative gravitational action in (4 +D)-dimensional space-time withS ^D as a compact manifold. It is found that the resulting four-dimensional theory for riccions is one-loop multiplicatively renormalizable. Renormalization group equations are solved and its solutions yield many interesting results such as (i) dependence of extra dimensions on the enegy mass scale showing that these dimensions increase with the increasing mass scale up toD = 6, (ii) phase transition at 3.05 × 10¹⁶ GeV and (iii) dependence of gravitational and other coupling constants on energy scale. Results also suggest that space-time above 3.05 × 10¹⁶ GeV should be fractal. Moreover, dimension of the compact manifold decreases with the decreasing energy mass scale such thatD = 1 at the scale of the phase transition. Results imply invisiblity of S¹ at this scale (which is 3.05 × 10¹⁶ GeV).