Dynamically generated parton distributions for high energy collisions

The parton distributions of the nucleon are evaluated dynamically using the assumption that at some low resolution scale the nucleon consists entirely of valence quarks. A simple parametrization of the resulting gluon distribution is presented, forx? 10^?5 up toQ ²?10⁶ GeV². This gluon distribution is predicted dicted to be much steeper and larger in the very smallx region (x<10^?2) than usually assumed. Applications to deep inelastic scaling violations and heavy quark (c, b, t) contribution are discussed and presented as well as hadronic heavy quark production at SSC/LHC energies. For example, the \(b\bar b\) production rate at 40 TeV is predicted to be about an order of magnitude larger than that estimated with other gluon distributions so far.     

Hadronic contributions to (g−2) of the leptons and to the effective fine structure constant α(M Z 2 )

The new experiment planned at Brookhaven to measure the anomalous magnetic moment of the muona _μ≡(g _μ?2)/2 will improve the present accuracy of 7 ppm by about a factor of 20. This requires a careful reconsideration of the theoretical uncertainties of theg?2 predictions, which are dominated by the error of the contribution from the light quarks to the photon vacuum polarization. This issue is cruicial also for the precise determination of the running fine structure constant at theZ-peak as LEP/SLC experiments continue to increase their precision. In this paper we present an updated analysis of the hadronic vacuum polarization using all presently availablee ⁺e^? data. This seems to be justified because previous work on the subject was based to some extent on preliminary or incomplete experimental data. Contributions from different energy ranges are presented separately forg?2 of the muon and the τ-lepton and for α(M _Z ² ). We obtain the resultsa _μ ^had* =(725±16)×10^?10 anda _τ ^had* =(351±10)×10^?8, where the asterisk indicates the dressed (renormalization group improved) value. For the effective fine structure constant atM _Z=91.1888 GeV we obtainΔα _had ⁽⁵⁾ =0.0280±0.0007 and α(M _Z ² )^?1=128.896±0.090. Further improvement in the accuracy of theoretical predictions which depend on the hadronic vacuum polarization requires more precise measurements ofe ⁺e^? cross-sections at energies below about 12 GeV in future experiments.     

The anomalous magnetic moment of positive and negative muons

The anomalous g-factor a ≡ (g?2)/2 has been measured for muons of both charges in the Muon Storage Ring at CERN. The two results, a_μ⁺ = 1165910(12) × 10^?9 and a_μ^? = 1165936(12) × 10^?9, are in good agreement with each other, and combine to give a mean a_μ = 1165922(9) × 10^?9, which is very close to the most recent theoretical prediction 1165921(10) × 10^?9. For the experimental results, the total statistical and systematic error is given. The measurements thus confirm the remarkable QED calculation plus hadronic contribution, and serve as a precise verification of the CPT theorem for muons.     

New measurement of (g−2) of the Muon

The g-factor anomaly, a≡(g?2)/2, has been measured for μ⁺ in the new Muon Storage Ring at CERN. The result is a = (1 165 895 ± 27) × 10^?9. This is (13 ± 29) × 10^?9 below the theoretical value which includes sixth-order QED terms and a hadronic contribution of (73 ± 10) × 10^?9.     

Measurement of the longitudinal structure function and the smallx gluon density of the proton

At HERA energies the smallx region (x?10^?2) can be explored atQ ² values large enough that leading twist QCD calculations are valid. We show how measurement of the longitudinal structure function,F _L (x,Q ²), can lead to accurate measurement of the gluon structure function at such smallx values. Experimental systematic errors are discussed fully and requirements for the measurement outlined. We conclude that it should be possible to distinguish between the widely varying gluon distributions which are currently allowed.     

Analysis of the hadronic light-by-light contributions to the muon g − 2

We calculate the hadronic light-by-light contributions to the muon g − 2. We use both 1/N_c and chiral counting to organize the calculation. Then we calculate the leading and next-to-leading order in the 1/N_c expansion low energy contributions using the Extended Nambu-Jona-Lasinio model as hadronic model. We do that to all orders in the external momenta and quark masses expansion. Although the hadronic light-by-light contributions to muon g − 2 are not saturated by these low energy contributions we estimate them conservatively. A detailed analysis of the different hadronic light-by-light contributions to muon g − 2 is done. The dominant contribution is the twice anomalous pseudoscalar exchange diagram. The final result we get is a_μ^{light-by-light} = (−9.2 ± 3.2) × 10⁻¹. This is between two and three times the expected experimental uncertainty at the forthcoming BNL muon g − 2 experiment.     

EPR of Cu2+ Impurities in Cytosine Hydrochloride: A Case of Superhyperfine Structure

Electron paramagnetic resonance spectra of Cu²⁺ impurities in cytosine hydrochloride single crystals are observed at liquid nitrogen temperature. Two magnetically equivalent sites for Cu²⁺ have been observed. The parameters of ⁶³Cu obtained with the fitting of spectra to rhombic symmetry spin Hamiltonian are: g _x  = 2.047 ± 0.002, g _y  = 2.187 ± 0.002, g _z  = 2.390 ± 0.002, A _x  = (86 ± 3) × 10^?4 cm^?1, A _y  = (87 ± 3) × 10^?4 cm^?1, and A _z  = (138 ± 3) × 10^?4 cm^?1. The observed bands in optical spectra of the single crystal recorded at room temperature are assigned to various d–d and charge-transfer transitions. Using both EPR and optical data, the nature of bonding of metal ion with different ligands is discussed.     

Electron Paramagnetic Resonance and Electron Spin Echo Studies of Co2+ Coordination by Nicotinamide Adenine Dinucleotide (NAD+) in Water Solution

Co²⁺ binding to the nicotinamide adenine dinucleotide (NAD⁺) molecule in water solution was studied by electron paramagnetic resonance (EPR) and electron spin echo at low temperatures. Cobalt is coordinated by NAD⁺ when the metal is in excess only, but even in such conditions, the Co/NAD⁺ complexes coexist with Co(H₂O)₆ complexes. EPR spin-Hamiltonian parameters of the Co/NAD⁺ complex at 6 K are g _z  = 2.01, g _x  = 2.38, g _y  = 3.06, A _z  = 94 × 10^?4 cm^?1, A _x  = 33 × 10^?4 cm^?1 and A _y  = 71 × 10^?4 cm^?1. They indicate the low-spin Co²⁺ configuration with S = 1/2. Electron spin echo envelope modulation spectroscopy with Fourier transform of the modulated spin echo decay shows a strong coordination by nitrogen atoms and excludes the coordination by phosphate and/or amide groups. Thus, Co²⁺ ion is coordinated in pseudo-tetrahedral geometry by four nitrogen atoms of adenine rings of two NAD⁺ molecules.     

Fourth forbidden beta decays of50V

The half lives ofβ ^? decay ande ^? capture in theΔJ=4 transitions of⁵⁰V were calculated in the formulation of Behrens and Schülke. The expression of formulas for these half lives are divided into two parts. The ones are common factors which depend on the lepton wave functions only. The other parts are nuclear parameters which change their values by choosing suitable nuclear models. We tabulated the numerical values of these common factors. As an example, we evaluated these parameters in a single particle shell model, and obtained the half lives 9.04×10¹⁷ years and 1.51×10¹⁶ years for theβ ^? decay ande ^? capture, respectively. The recent experimental data measured by A.J. Pape et al. aret _1/2>7.0×10¹⁷ years for theβ ^? decay andt _1/2>8.8×10¹⁷ years for thee ^? capture. In the case of thee ^? capcure, the screening effects of the other orbital electrons were properly taken into account.     

Hyperfine and nuclear quadrupole interactions in copper-doped cadmium oxalate trihydrate single crystals

Electron spin resonance experiments on Cu²⁺ doped in a single crystal of cadmium oxalate trihydrate grown by a slow diffusion technique have been carried out at 77 K. The major features of the ESR spectra can be attributed to divalent copper (3d⁹) in substitutional Cd²⁺ sites. Information has been gained about the hyperfine and quadrupole interactions concerning the ion. The spin-Hamiltonian parameters in the $\text{S =}\text{1}\text{2}$, $\text{I =}\text{3}\text{2}$ manifold are: g_x = 2.0211; g_y = 2.2249; g_z = 2.4536; A_x = +84.5 × 10^?4cm^?1; A_y = +16.8 × 10^?4cm^?1; $\text{A}{}_{\mathrm{z}}\text{= ?40.8 × 10 ×}{}^{\mathrm{?4}}\text{cm}{}^{\mathrm{?1}}$; P_x = ?7.4 × 10^?4cm^?1; P_y = ?0.4 × 10^?4cm^?1; and P_z = +7.8 × 10^?4cm^?1. An evaluation of the asymmetry and quadrupole coupling parameters revealed that the ground state of the guest ion in Cd(COO)₂ · 3H₂O is 0.97|x² ?y₂ > +0.24 |3z² ? r² >.     

New evaluation of muon (g − 2) hadronic anomaly

The hadronic part a_H of the muon g-factor anomaly $\text{a ≡}\text{(g ? 2)}\text{2}$ is evaluated from latest data on σ(e⁺e^? → hadrons). For a p-wave ππ scattering length of a₁ = 0.04±0.005 we calculate a_H = (66±10) × 10^?9, compared to a(experiment) ? a(QED) = (60±29) × 10^?9. Half of the uncertainty on a_H is associated with the energy interval $\text{0.92 <}\text{s}\text{< 2}\text{GeV}$.     

ESR and optical study of Cu2+-doped bis-(5,5′-diethylbarbiturato)bis picoline Zn(II)

ESR studies were conducted on Cu²⁺-doped bis-(5,5′-diethylbarbiturato)bis picoline Zn(II). Two Cu²⁺ lattice sites, Cu²⁺(I) and Cu²⁺(II), were identified. These sites exhibit two sets of four hyperfine lines in all directions. The g factor and hyperfine splitting were calculated from ESR absorption spectra: g_x ?=?2.0201?±?0.002, g_y ?=?2.0900?±?0.002, g_z ?=?2.1634?±?0.002, A_x ?=?(30?±?2)?×?10^?4?cm^?1, A_y ?=?(40?±?2)?×?10^?4?cm^?1 and A_z ?=?(154?±?2)?×?10^?4?cm^?1. It was found that Cu²⁺ enters the lattice substitutionally. The ground-state wavefunction of the Cu²⁺ ion in this lattice was determined from the spin Hamiltonian constants obtained from the ESR studies. With the help of an optical absorption study, the nature of the bonding in the complex is also discussed.     

EPR and Optical Absorption Study of VO2+-Doped Lithium Hydroxylammonium Sulphate

ABSTRACT

Single-crystal and powder EPR studies of VO²⁺-doped lithium hydroxylammonium sulphate (LiNH₃OHSO₄) were carried out at room temperature. The results indicate the presence of two magnetically inequivalent VO²⁺ sites. The VO²⁺ ion takes up a substitutional position in the host lattice. The angular variation of EPR spectra in three mutually perpendicular planes were used to determine the spin Hamiltonian parameters, and the values obtained were the following: For Site 1, g_x = 2.0249 ± 0.0002, g_y = 1.9698 ± 0.0002, g_z = 1.9552 ± 0.0002, A_x = (51 ± 2) × 10^?4 cm^?1, A_y = (93 ± 2) × 10^?4 cm^?1, and A_z = (165 ± 2) × 10^?4 cm^?1; and for Site 2, g_x = 2.0267 ± 0.0002, g_y = 1.9743 ± 0.0002, g_z = 1.9213 ± 0.0002, A_x = (40 ± 2) × 10^?4 cm^?1, A_y = (80 ± 2) × 10^?4 cm^?1, and A_z = (155 ± 2) × 10^?4 cm^?1. The optical absorption spectrum recorded at room temperature shows four bands. From the optical and EPR data, various molecular coefficients are evaluated, and the nature of bonding in the crystal is discussed.     

Raman gain,effectiveg-value and spontaneous spin-flip Raman linewidth in Hg0.77Cd0.23Te

We report on measurements of spin-flip Raman gain inn-Hg_1?x Cd _x Te (x=0.23, carrier density 1.0×10¹⁵cm^?3) as a function of the magnetic field up to 1.6T. The measurements were carried out by a small signal gain technique at a temperature of 1.8 K. Furthermore, the measurements yield lineshapes and linewidths of the spontaneous scattering and allow a precise determination of the effectiveg-value. The highest gain observed is 0.2 cm/W. The band edge value of the effectiveg-value is ?93.2 and the widths of the symmetric lines are between 18 and 120 G, depending on the magnetic field.     

Na+ ion conductivity and crystallographic cell characterization in the Hf-nasicon system Na1+xHf2SixP3−xO12

We have measured the effect of varying the mobile ion concentration on the sodium ion conductivity in the Hf-Nasicon system, Na_1+xHf₂Si_xP_3-xO₁₂, for 1.4 ? x ? 2.8. The conductivity is greatest for Na_3.2Hf₂Si_2.2 P_0.8O₁₂: σ_25°C = 2.3 × 10^?3 (ω cm)^?1, and σ_250°C = 1.7 × 10^?1 (ω cm)^?1. These values are approximately 50% greater and worse, respectively, than the values reported for the best Zr-Nasicon. We have characterized the variation of lattice parameters with composition and found the behavior to be similar to that of Zr-Nasicon. A small distortion from rhombohedral to monoclinic symmetry occurs for compositions 1.8 ? x ? 2.2.     

Nuclear magnetic resonance of intermetallic compounds Gd2Ni17−xAlx

²⁷Al Knight shifts vs temperature and magnetic susceptibility for the intermetallic compounds Gd₂Ni_17?xAl_x (x = 17; 16.2; 16; 15) are presented. The results are discussed in terms of the uniform polarization model fo the conduction electrons by the 4f and 3d spins localized on the Gd and Ni ions. The phenomenological exchange constants J_sf and J_sd range between ?1.80×10^?3 and 1.19×10^?3 eV and ?0.63×10^?3 and ?0.52×10^?3 eV, respectively.     

Ionic conductivity of Zr1−xIn2xO2−x

As x in Zr(In)O_2?x is increased from 0.08 to 0.16 (9–19 mole per cent In₂O₃) the activation energy E(x) for ionic conduction increases from 1.05 to 1.51 eV; the concuctivity decreases from 2 × 10^?5 to 3 × 10^?6Ω^?1cm^?1at 400°C, is composition-independent at about 580°C, and increases from 1 × 10^?2 to 4 × 10^?2Ω^?1cm^?1 at 800°C. The pre-exponential term of the Boltzmann-type conductivity equation depends exponentially on E(x), a much stronger dependence on x than theoretically expected with a model for ionic conductivity that includes nearest-neighbor defect interactions. Analysis of reported conductivity data for Zr(M)O_2?x (M = Sc, Y, Ca and rare earth metals) and other doped oxide electrolytes with fluorite-type structure reveals that the same relationship is observed with these materials when x γ0.08. It is shown that ionic conduction in these oxides is consistent with nearest neighbor vacancy-cation defect interaction forx < 0.08 but that an additional complex interaction with composition-dependent free energy ΔG(x) occurs when xγ 0.08.The lattice constant of Zr(In)O_2?x with the cubic fluorite-type structure is independent of composition, 5.114 ± 0.002 Å, in agreement with ionic size considerations.     

Experimental information on the pion gluon distribution function

An experiment performed at Fermilab used double-arm calorimeter triggers to study di-jet production by 400 GeV protons and 200 GeVπ ^? mesons incident on liquid hydrogen. The observed ratio of positive to negative leading particles in the jets was compared forpp andπp production using a tree level parton scattering model. The results are moderately sensitive to the form of the pion gluon distribution function and yieldx g(x)?(1?x)^{2.75±0.40±0.75}.     

Radiative decay ofJ/ψ into γ π+ π−

The radiative decayJ/ψ → γ π⁺ π^? has been studied using the 8.6 millionJ/ψ produced in the DM2 experiment at the DCIe ⁺e^? storage rings at Orsay. The π⁺ π^? mass spectrum shows a cleanf ₂ (1270) signal, and the possible presence of two other states at thef ₂ (1720) andf ₄ (2030) masses. For thef ₂ (1270), the branching ratio BR(J/ψ →γf)xBR(f→π⁺ π^?) is measured to be (7.50±0.30±1.12)×10^?4, and the spin analysis prefers theJ=2 assignment, with helicity parametersx=0.83±0.06 andy=0.01±0.06. The existence of higher mass states is discussed.     

Atomic beam measurement of the lifetime of the3 P 1 metastable states of Mg and Ca

The lifetime of the metastable level³ P ₁ of Mg and Ca have been measured in an atomic beam experiment. We excite the atoms to the³ P ₁ state by electron collisions and we measure the decay length of the light emitted by the beam. The velocity distribution of the atoms is also measured by a time-of-flight technique. The decay length and the velocity measurements are then combined to compute the required lifetimes. The results are (2.4±0.2)×10^?3 sec for Mg and (0.55±0.04)×10^?3 sec for Ca.