A test of the Lorentz structure of semi-hadronic τ decays

A method is proposed for the determination of the Lorentz structure of the electroweak interaction in semi-hadronic τ decays. Spin correlations in the process $$e^ + e^ - \to \tau ^ + \tau ^ - \to \bar v_\tau \pi ^ + \pi ^0 v_\tau \pi ^ - \pi ^0 $$ are exploited for a measurement of the normalized product, γ_AV = 2Re{g_Ag _V ^* }/(|g_V|² + |g_V|²), of the vector (g _V ) and axial vector (g _A ) coupling of the τ lepton. The contribution of scalar (g _S ) or pseudo-scalar (g _P ) couplings is also investigated. Since in the above process the direction of flight of the τ leptons can be reconstructed up to a twofold ambiguity a likelihood method using the whole kinematic information can be employed. The matrix element entering the likelihood function has been evaluated in terms of the momenta and angles of the observed pions. The sensitivity of the derived method in ane ⁺ e ^? energy region around 10 GeV has been investigated for the ARGUS experiment using Monte Carlo simulations.     

Vector boson in the constant electromagnetic field

The propagator and the complete sets of in-and out-solutions of the wave equation, together with the Bogoliubov coefficients relating these solutions are obtained for the vector W-boson (with the gyromagnetic ratio g=2) in a constant electromagnetic field. When only the electric field is present, the Bogoliubov coefficients are independent of the boson polarization and are the same as for the scalar boson. For the collinear electric and magnetic fields, the Bogoliubov coefficients for states with the boson spin perpendicular to the field are again the same as in the scalar case. For the W ^? spin parallel (antiparallel) to the magnetic field, the Bogoliubov coefficients and the one-loop contributions to the imaginary part of the Lagrange function are obtained from the corresponding expressions for the scalar case by the substitution m ² → m ²+2eH (m ² → m ²-2eH). For the gyromagnetic ratio g=2, the vector boson interaction with the constant electromagnetic field is described by the functions that can be expected by comparing the scalar and Dirac particle wave functions in the constant electromagnetic field.     

CVC for gluons and hadroproduction of quark flavours

We investigate the phenomenological implications of the straightforward extension of the conserved vector current hypothesis to gluons. The characteristics of strange, charmed particle and ψ production cross sections in hadron collisions are successfully obtained from experimental data on the production of virtual photons, rescaled by a factor α_g²(M)/α²·α_g(M) is the quark-gluon coupling constant, varying with the gluon mass M in the sense of asymptotic freedom.     

Deep inelastic lepton-hadron scattering in massive vector gauge models

A class of strong interaction models in which the interactions between fractionally charged colored quarks are mediated by massive neutral vector gluons is considered. All the vector gluons acquire masses via the usual Higgs mechanism. The effective coupling constants $\text{g}$ (gauge coupling) and $\text{h}$ (quartic self-coupling) are supposed to approach a limit cycle in the limit of large space-like momenta. The large Q² behavior of the moments of the deep inelastic lepton-hadron structure functions is analysed using this hypothesis. It is shown that Bjorken scaling is violated by power terms of Q² multiplied by an oscillating function of Q².     

Production cross section and electroweak asymmetry of D* and D mesons produced in e+e− annihilations at 29 GeV

The production of D^* and D mesons has been studied in e⁺e⁻ annihilations at √s = 29GeV. The data, corresponding to an integrated luminosity of 300 pb⁻¹, were obtained using the HRS detector at PEP. The cross section is measured to be R (D⁰ + D⁺) = 2.40±0.35 and we determine the electroweak asymmetry to be −9.9 ± 2.7%, which corresponds to an axial vector coupling constant product g^eg^c = 0.26 ± 0.07.     

Half-life andg-factor of the 11/2− isomeric states in115Sb and117Sb

Using the time-differential perturbed angular distribution method (TDPAD) theg-factors of the 11/2^? isomeric states in¹¹⁵Sb and¹⁷Sb have been measured to beg(¹¹⁵Sb, 11/2^?)=0.97 ±0.10 andg(¹¹⁷Sb, 11/2^?)=1.02 ±0.07. The experimental half-lives and theg-factors are compared to the single-particle estimates.     

Solitons in the Nambu-Jona-Lasinio model with vector and axial mesons

We study the effect of vector and axial isovector mesons in the soliton of the SU(2) NJL-model for static hedgehog configurations and on the chiral circle. The Lagrangian reproduces Sakurai's Universality and implements vector dominance through current-field identities. The parameters of the Lagrangian are fixed by means of a heat-kernel expansion up to second order taking theA-π mixing into account. For the corresponding set of parameters we find solitons for constituent quark masses betweenM～265–345 MeV which are much lower than those found without vector mesons. For the valueM=315 MeV which corresponds both to the KSFR relation 2g _ρ ² f _π ² =m _ρ ² and the Weinberg sum rule m _A ² =m _ρ ² the soliton has a clearly negative quark eigenvalue. The soliton mass is about 1100 MeV. For this choise of parameters the radius and axial coupling constant turn out to be too small.     

Absorption spectrum of VO2+ in zinc cesium sulphate hexahydrate

Results of optical absorption spectra of VO²⁺ ion doped in zinc cesium sulphate hexahydrate are reported. The observed bands have been assigned transitions from the ground ²B_2g state to the excited ²E_g, ²B_ig and ²A_1g states. From the nature and position of the bands a successful interpretation of all observed bands could be made. The crystal field and molecular orbital coefficients are reported.     

CW Optical-Optical Double Resonance studies of the 23Πg, 33Πg, 43Πg+, and 13Δg Rydberg states of Na2

The 2³Π_g, 3³Π_g, 4³Σ_g⁺, and 1³Δ_g states of the Na₂ molecule are observed by sub-Doppler Perturbation Facilitated Optical-Optical Double Resonance (PFOODR) spectroscopy. Absolute vibrational assignments and molecular constants are obtained for two of these states (3³Π_g, v = 0–25 observed, and 4³Σ_g⁺, v = 3–5, 13, 14 observed). Tentative vibrational assignments and provisional molecular constants are obtained for the 2³Π_g (v = 43–89 observed) and 1³Δ_g (v = 31–35, 40, 46–51 observed) states. Spin-orbit, spin-spin, and hyperfine splittings are observed. The direct ³Λ_g⁺ → a³Σ_u, 2³Π_g ∼ 3³Π_g perturbation-induced, and collision-induced contributions of these four ³Λ_g states to the ubiquitous Na-vapor violet and ultraviolet emission bands are discussed.     

Messung der magnetischen Momente der tiefsten 2+-Zustände für einige Dy-, Er- und Yb-Isotope

With the Mössbauer technique, the hyperfine splittings of the lowest 2⁺-states of some Dy-, Er-, and Yb-isotopes were observed at 4.2 °K in the paramagnetic compounds Dy-Al-garnet, ErCl₃·6H₂O, and YbCl₃·6H₂O. Most of the sources were produced by photonuclear reactions. Ratios ofg-factors for neighbouring isotopes could be determined with small systematic errors. The results are:g ¹⁶⁴/g ¹⁶⁶=1.103 (15),g ¹⁶⁶/g ¹⁶⁸=0.960 (13) for Er, andg ¹⁷⁰/g ¹⁷²=1.009 (15),g ¹⁷⁰/g ¹⁷⁴=0.994 (13) for Yb. Using known values for the effective magnetic fields at the nuclei, the followingg-factors were obtained:¹⁶⁴Dy 0.336 (14),¹⁶⁴Er 0.353 (10),¹⁶⁶Er 0.320 (8),¹⁶⁸Er 0.333 (8),¹⁷⁰Yb 0.335 (6),¹⁷²Yb 0.332 (8),¹⁷⁴Yb 0.337 (8).     

The anomalous quasi isotropic [g] tensor found for CdBr2:Ag2+ and AgBr0.15Cl0.85:Ag2+: An explanation through strong covalency

The “anomalous” quasi-isotropic [g] tensor observed in systems containing the elongated AgBr⁴⁻₆ unit (g_∥ = 2.078 ± 0.003; g⊥ = 2.065 ± 0.003) is reasonably explained, within a rigorous Molecular Orbital framework, in terms of a very high covalency, consistent with the optical electronegativity of Ag²⁺ and previous results on other Cu²⁺ and Ag²⁺ complexes. For the antibonding level 3b_1g(x² − y²) about 90% of the electronic charges should be on bromine ions. The present analysis reveals that g_∥ − g₀ is dominated by charge-transfer excitations while g_⊥− g₀ is dominated by crystal-field excitations.     

Electron paramagnetic resonance and photoluminescence properties of α-Al2O3:Cr3+ phosphors

The red emitting Cr³⁺ activated α-Al₂O₃ powder phosphor has been prepared by easy combustion reactions from mixed metal nitrate reactants and urea with ignition temperatures of 500 °C. The as-synthesized powder was characterized by X-ray diffraction, scanning electron microscopy, and Fourier-transform infrared techniques. The X-ray diffraction pattern reveals that the phosphor crystallized in the hexagonal α-Al₂O₃ phase directly from the combustion reaction. The EPR spectrum exhibits an intense resonance signal with effective g value at g=3.33 along with a few weak resonance signals with effective g values at g=13.7, 2.34, 1.95, 1.49, and 1.26. The spin concentration (N) and its paramagnetic susceptibility (χ) have been evaluated. The excitation spectrum consists of two broad intense bands at 415 nm and 555 nm and are assigned to ⁴A_2g (F)→⁴T_1g (F) and ⁴A_2g (F)→⁴T_2g (F) transitions, respectively. The intense fluorescence peak around 691 nm is attributed to ²E _g →⁴A_2g transition of Cr³⁺ ion. By correlating EPR and optical data, the crystal field splitting parameter (Dq), Racah inter-electronic repulsion parameter (B) have been evaluated and discussed. The EPR and optical studies reveal that Cr³⁺ ions are occupying in Al³⁺ sites in octahedral coordination.     

Selective laser spectroscopy of Mn4+-Mn4+ pair centers in SrTiO3 crystal

Zero-phonon lines of a pair center of Mn⁴⁺ ions are observed in the luminescence and luminescence-excitation spectra of SrTiO₃:Mn crystal. Based on the experimental data, the energy-level structure of the ground state ∣⁴ A _2g ,⁴ A _2g 〉 and excited state ∣⁴ A _2g ,² E _g 〉 of the Mn⁴⁺-Mn⁴⁺ pair center is constructed. It is shown that the exchange interaction in the ground state of the Mn⁴⁺-Mn⁴⁺ pair is antiferromagnetic. Energies of the levels are calculated assuming that the pair is formed by Mn⁴⁺ ions occupying neighboring octahedral positions of Ti⁴⁺ ions along the [110] axis. Experimental values of the exchange integral in the ground state ∣⁴ A _2g ,⁴ A _2g 〉 and energies of spin multiplets in the excited state ∣⁴ A _2g ,² E _g 〉 agree well with calculation of the exchange interaction carried out within the framework of the channel model with the parameters J _ξη = 32 cm^4-1 and J _ζζ = ?45.5 cm^4-1. Experimental data and calculations unambiguously demonstrate that zero-phonon lines in the luminescence and luminescence-excitation spectra have magnetic-dipole nature.     

Electroweak tests with τ leptons at LEP

We report on two sensitive tests of lepton universality carried out by the 4 LEP experiments at the Z⁰ pole. From measurements of the τ polarization in e⁺ e^?→τ ⁺ τ ^?, the ratios of the vector and axial vector coupling constants of the electron and the tau lepton to the weak neutral current are obtained to beg _{v e} /g _{a e} =0.066±0.015 andg _{V τ} /g _{A τ} =0.070±0.009 respectively. From measurement of the τ lifetime and the τ leptonic branching ratios, the ratio of the coupling constants describing weak leptonic decays of the τ and the μ is measured to beG _τ /G _μ =0.996±0.008.     

Anomalies in the orbital magnetism of neutrons in the 190,192Pt nuclei

For the ^190,192Pt nuclei, the g factors of the ν9/2^?[505]?ν11/2⁺[615] 10^? isomeric states populated in the relevant (α, 2n) reactions are measured by the method of an integrated disturbed angular distribution in an external magnetic field. From these measurements, it follows that the g factors are 0.009(8) and 0.010(6) for ¹⁹⁰Pt and ¹⁹²Pt, respectively. From the above g factors, it is found that the anomalous g _l factor of the neutron is δg _l(n)=?0.017(6).     

Photoionization of molecular oxygen in the X3Σg− and a1Δg states

Calculations are carried out, at similar levels of approximation, of the photoionization cross-sections for the ground X³Σ_g^? and metastable a¹Δ_g states of O₂ leading to the X²Π_g state of O₂⁺. Estimates, based upon measurements for the X³Σ_g^? state, are made of the photoionization cross-section of the a¹Δ_g state for transitions populating excited states of O₂⁺.     

Theg-factor of the first 2+ state in192Pt by measurement of recoil into vacuum

Perturbed γ-ray angular distributions from the first 2⁺ states were measured for Coulomb-excited^{192,194,196,198}Pt recoiling into vacuum atv/c=0.010. Comparableg-factors were obtained for all four nuclei. Normalisation to the hyperfine field in¹⁹⁶Pt enabled both a comparison with a recent hydrodynamicg-factor measured in¹⁹²Pt and a cross-check of disputed Ir in Fe measurements. The followingg-factor was obtained:g(316 keV, 2⁺;¹⁹²Pt)=0.32(3).     

Spectral decomposition of an elementary 3-fermion 2-body operator

The eigenvalues and eigenfunctions of an elementary 3-fermion 2-body operator 3P²_g∧I¹A³∑_{1≤i≤j≤3}P²_g(i, j)A³ acting on a 3-particle antisymmetric finite-dimensional Hilbert space have been found. Here P_g² denotes the projection operator onto a 2-particle antisymmetric function g², while A³ denotes the 3-particle antisymmetrizing operator.     

Gell-Mann-Low function in QCD

The Gell-Mann—Low function in QCD β(g)(g=?²/16π², where ? is the coupling constant in the Lagrangian) is shown to behave in the strong-coupling region as β_∞ g ^α, where α≈?13 and β_∞～10⁵.     

Precision measurements of the nuclear magnetic dipole moments of6Li,7Li,23Na,39K and41K

Using the atomic beam magnetic resonance method and using the technique of separated oscillatory fields in combination with the triple resonance method the ratiosg _I /g _J of the stable alkali isotopes Li, Na and K in the²S_1/2-ground state have been measured at magnetic fields of about 3 kOe. Frequency shifts analogous to the Bloch-Siegert-shift, expected from theory, were observed and eliminated by extrapolation to vanishing rf-field strength. The results, uncorrected for atomic diamagnetism, are:⁶Li:g _I /g _J =?0.22356978(10)·10^{?3 7}Li:g _I /g _J =?0.59042719(10)·10^{?3 23}Na:g _I /g _J =?0.40184406(40)·10^{?3 39}K:g _I /g _J =?0.07088613 (6)·10^{?3 41}K:g _I /g _J =?0.03890837 (4)·10^?3 Furthermore, the hyperfine structure splitting constants in the² S _1/2-ground states have been determined. Using the most precise absoluteg _J -values available so far one can calculate absolute values for the uncorrectedg _I - factors. The results are:Δν/MHz ?g _I·10^{3 6}Li: 228.2052590(30) 0.4476540 (3)⁷Li: 803.5040866(10) 1.1822130 (6)²³Na: 1771.6261288(10) 0.8046108 (8)³⁹K: 461.7197202(14) 0.14193489(12)⁴¹K: 254.0138720(20) 0.07790600 (8) By comparing the absoluteg _I - factors with measurements received by the NMR-method, the chemical shifts of the NMR-frequencies caused by the hydrate surrounding of the alkali ions in the NMR-probe are determined.