Table of contents

A perturbative QCD approach to the production of `naked' heavy flavour states in pp and p interactions is outlined. The subprocesses considered are: q → c and gg → c (flavour creation), qc → qc and gc → gc (flavour excitation). Calculated cross sections are presented, and discussed in the light of present experimental results for the hadronic production of charm. Although their calculation has substantial uncertainties, the flavour excitation processes, contrary to intuitive expectation, may be the dominant mechanism.

The assumptions on the initial state in the Landau hydrodynamical model are difficult to accommodate inside the present ideas on the dynamics in hadron-hadron collisions, in particular in connection with the leading particle properties. The model is generalized to permit an interpretation in terms of the notions employed in the valence-quark-gluon models of the van Hove-Pokorski type. The main assumption is that the valence quarks in general will pass by each other leaving the (neutral) remainder of the hadronic matter in a state described by a simple wave mode of an ideal relativistic gas. In such a state there is a precise coupling between the internal state (described by temperature) and the state of motion of the fluid elements. In particular, some parts of the hadronic matter are at rest at high temperature, while other parts are "carried away" by the valence quarks with a temperature decreasing with increasing velocity. We assume that some parts of this hadronic matter which are left in a state with rapidity less than a constant y₀ develop into the final state principles populating the centre of phase-space. In this case there is a one-to-one correspondence between the initial state of the hadronic matter and the asymptotic energy and multiplicity distributions of the secondaries in the center of phase-space. Formulas permitting a determination of this initial state from experimental results are derived and some simple examples analyzed.

The angular distribution of large transverse momentum muon pairs produced in hadron-hadron collisions is calculated in lowest order of perturbative QCD.

It is shown that for the process quark + antiquark → gluon + μ⁺μ^- the polar and azimuthal angle distributions can be made independent of the parton distributions by choosing a special reference frame, the Collins-Soper frame, but for the process quark + gluon → quark + μ⁺μ^- this is not possible.

By means of width measurements with a filar micrometer the charges of nuclei stopping in nuclear emulsion can be determined. The method of measurement is tested on tracks of 100 stopping cosmic ray nuclei of known nuclear charge Z = 5-26 in G5-emulsion in the residual range interval 0 ⩽ R ⩾ 400 μm. The widths are measured according to a special procedure of measurement.

The study shows that it is possible to apply the method of identification on low energy heavy nuclei stopping in the emulsion. The method is a valuable complement to photometric methods at residual track ranges less than 400 μm and is to advantage applicable to fragments emitted in nucleus-nucleus interactions in emulsion at least if the dip angles of the fragments are less than about 35°.

Elastic and the 3⁺ inelastic scattering of 0.6 and 1.04 GeV protons on ⁶Li have been calculated in the α-d cluster model using Glauber multiple scattering theory. It is found that but for the elastic scattering beyond the first diffraction minimum, the predictions of the commonly used Gaussian cluster model agree with experiment fairly well. It seems the disagreement beyond the first diffraction minimum is largely due to the limitations of the model to describe the large momentum transfer behaviour of the target.

The propagation of neutrons in thick paraffin and lead layers was examined in the energy range 0.001 eV-20 MeV. The total frequencies of the neutron occurrence, the frequency distributions of certain lateral displacements of neutrons, the frequency distributions of the neutron occurrence in certain energy regions and occurrence frequencies in certain time intervals were calculated by Monte-Carlo methods as functions of the depths in the materials. Experimental values were used for the total and differential cross sections of different kinds of neutron-nucleus collisions, but for differential cross sections, theoretical estimates were also needed in certain regions. The initial energies of neutrons were 1, 10, and 20 MeV. The effect of the exceeding of the threshold of inelastic reactions in n-C and n-Pb collisions on the frequencies of neutron occurrence was also investigated. The results demonstrate that the frequency of neutron occurrence in lead in different depths is at least one order of magnitude greater than in paraffin. Thus, by combining these two materials in different ways the shape of the occurrence frequency and its absolute height can be modified considerably.

The radiative corrections to the meson-nucleon verticies of I = 1 and I = 0 scalar, pseudoscalar and vector mesons are derived using the standard Feynman technique. For neutral mesons the radiative corrections gives charge asymmetric contribution to the two-nucleon potential. Using the charge symmetry breaking contribution to the One-Boson-Exchange-Potential models due to radiative corrections of scalar, pseudoscalar and vector mesons, we calculate the charge asymmetric energy Δn in ³He-³H nuclei. We find Δn = 0.009 and 0.007 MeV for different OBEP models. This is too small to explain the observed discrepancy. The results seem to be consistent with earlier calculations.

The absolute values of the oscillator strength f were measured for the spectral lines of erbium (λ₁ = 386.285 nm, λ₂ = 400.797 nm, λ₃ = 415.111 nm) by means of the absorption method with the atomic beam acting as an absorbent. The product Nl of the atomic density of the absorbing beam N and of the thickness of the absorbing layer l was measured with an electronic microbalance. The values of f which were obtained are: 0.56 ± 0.14, 0.71 ± 0.18, 0.39 ± 0.10 respectively.

The natural linewidths of Lα₁ X-ray emission of metallic In and Sn have been measured in fluorescence by using a high resolution double crystal spectrometer and found to be 2.83 and 2.86 ± 0.15 eV, respectively. The diagram Lα_1,2 lines exhibit high-energy satellites which originate most probably from Coster-Kronig transitions and shakeoff.

In order to prepare a theoretical analysis of Rydberg series 4f¹⁴ 6snl the classification of the spectrum of neutral ytterbium has been extended with the help of new observations in the infrared and measurements of Zeeman effect in the visible and near ultraviolet. 176 lines are classified by 70 new levels. The configurations 4f¹³6s²6p and 4f¹⁴6p² are now complete and the lowest levels of 4f¹³5d²6s and 4f¹⁴5d6p have been recognized, as well as new low members of the Rydberg series.

In both parities a parametric study of the configurations taking into account mixing effects has led us to revise and to extend the earlier labeling. All the perturbers of the 4f¹⁴6snl series have been found or predicted. A reinterpretation of the autoionizing levels observed by Parr and Elder is also needed.

The beam-foil technique has been applied to study the iodine spectrum. New assignments are given for the I VI transitions 5s²¹S₀-5s5p¹P₁⁰, 5s²¹S₀-5s5p³P₁⁰, 5s5p³P₀⁰-5s5d³D₁, 5s5p³P₁⁰-5s5d³D₂, 5s5p³P₂⁰-5s5d³D₃ and 5s5p¹P₁⁰-5s7s¹S₀, and tentatively for the I VII 4f-5g transition. Lifetimes have been measured for the 5s5p¹P₁⁰ and ³P₁⁰ levels of I VI and for the 5p²P⁰ levels of I VII. MCHF calculations have been performed for two multiplets in I VI and for two multiplets in I VII. The experimental energies of the three lowest ¹S terms are used to derive an I VI ionization potential of 72.9 eV.

Beam-foil excitation functions have been measured for some optical transitions in C II-C IV in the projectile energy range 100-450 keV, and in C IV-C VI from 4 to 20 MeV. The full set of population functions, representing eight different classes of core-outer shell arrangements, are reproduced by three parameters accounting for 1s vacancies, 2s vacancies, and outer shell populations according to the independent-electron model. The excitation functions at 4-20 MeV were measured with foils tilted 0°, 30° and 45° and the photon yields for C III-C VI lines found to depend substantially upon the foil tilt angle. Relative level populations were measured for some C IV levels. The results show that the relative level population within the same term series decreases slightly faster than n^-3. The relative population for fixed principal quantum number increases from s to p levels, decreases to d levels, and shows another increase from d to g levels. This relative level population picture is independent of foil tilt angle.

The Kα^h hypersatellite spectra of Ti, Cr, Fe and Ni have been measured in photon excitation with a plane crystal Bragg spectrometer. The experimental energies and relative intensities of Kα^h₁ and Kα^h₂ lines are obtained and compared with multiconfiguration Dirac-Fock calculations. The K shell double photoionization cross-sections are estimated from the experimental hypersatellite intensities. Experimental results agree with existing theoretical calculations based on the shake theory and correlated wave functions.

The collisional quenching rate-coefficient of electronically excited Br(4²P_1/2) atoms by N₂O molecules has been measured using the time-resolved fluorescence technique. The rates of deactivation of N₂O(00°1) by N₂O, Br₂, and inert gases (He, Ne, Ar, Kr, Xe, and SF₆) have also been measured. By comparing the intensities of Br(4²P_1/2) and N₂O(00°1) emissions, it was possible to determine the rate of Electronic to Vibrational energy transfer from Br(4²P_1/2) to the (00°1) level in N₂O. This rate was found to be (2.45 ± 0.7) × 10⁴ s^-1 Torr^-1.

Calculations of energies and lifetimes of levels for configurations 2s²2p⁵3l and 2s2p⁶3l were performed for the Mg, Si, S, Ar, Ca, Ti, V, Cr, Fe, Ni ions. The intermediate coupling scheme was used. The initial energy matrix was derived in the LS-scheme. Relativistic corrections were calculated using the Breit operator. Calculations were made in the framework of the Z-expansion perturbation theory.

Lifetime measurements using the beam-foil method are reported for the 2s3p³P_{0, 1, 2} levels in N IV, O V and F VI. The ³P₁ level lifetime is significantly shorter than those for ³P₀ and ³P₂. This is due to the 2s²¹S₀-2s3p³P₁ intercombination transition. From careful lifetime measurements at several ion energies we obtain transition probabilities of (3.3 ± 2.7) × 10⁶, (22 ± 6) × 10⁶ and (88 ± 9) × 10⁶ s^-1 for this spin-forbidden transition in N IV, O V and F VI, respectively. These results are supported by theoretical analyses.

A band of the emission spectrum of CuO located at 4182 Å is rotationally analyzed. It is the 0-0 band of the M²Π_3/2-X²Π_3/2 system. Some perturbations are studied. Molecular constants of the upper state are given.

The muon spin precession frequencies in the semimetals As, Sb and Bi have been studied as function of temperature and applied magnetic field. In Sb an anomalously large, temperature dependent and anisotropic Knight shift was found (at T = 2 K, K_iso = 0.9%, K_ax = 0.3%). The shift is small above 100 K. The results are qualitatively discussed in terms of two models: (i) a shallow donor state and (ii) as partly bound electron states at an impurity charge in a metal.

This large Knight shift is not found in As and Bi.

SQUID magnetometer measurements of the magnetic susceptibility (χ_|| and χ_⊥) of MnF₂ have been carried out in the temperature interval 4.2 to 300 K, with special emphasis paid to the region in the immediate vicinity of the Néel point. By combining our data with specific heat data from Teaney (Phys. Rev. Lett.14, 898, 1965) we have checked the validity of Fisher's relation between the magnetic specific heat C_m and the magnetic parallel susceptibility χ_||. Fisher's relation states:

C_m/R ≃ K ∂/∂T (χ_||T)

where K is a factor of proportionality nearly independent of temperature. We find that Fisher's relation is well obeyed in the temperature interval:

2 × 10^-4 < | T/T_N - 1| < 6 × 10^-2

The instantaneous distribution of vibrating atoms and translating atoms in a simulated two-dimensional liquid was found to be heterogeneous. Groups comprising between twenty and fifty atoms move with respect to each other by a mechanism which resembles grain-boundary sliding by dislocation-like displacements.

Surface or interface waves are often studied by simply matching two half media. Surface effects may involve changes in inertial (mass) or elastic properties. These are here treated as additional boundary conditions which modify the matching equations. The treatment includes extra surface forces in all possible directions, is based on the Surface Green function matching (SGFM) method and is developed in a way which applies equally to solids and to viscous fluids. Several problems concerning surfaces, interfaces and planar defects are discussed, as well as open questions concerning the connection between lattice dynamics models and their elastic limit. The formal analysis is extended to the case of layered media and the limit of infinitesimally small thickness of a layer is explicitly obtained and used to corroborate the above results.

A method for angular measurements through a series of plane gratings is described. In each grating an angular amplification takes place, when a monochromatic collimated beam is diffracted in series by the gratings. If Echelle gratings are used, a wider angular range can be spanned by counting the spectral orders from the last grating. The method is illustrated by simple experiments using four Echelles in series.

The decays of the isomeric 9/2⁺ states which have been produced by (d, pγ) and (³He, xnγ) reactions, have been investigated in three N = 89 nuclei. The half-lives have been determined to be 5.1 ± 0.3 ns in ¹⁴⁹Nd and 3.5 ± 0.4 μs in ¹⁵³Gd. In ¹⁵⁵Dy a 5.5 ns half-life was found, but we were unable to assign it to the 9/2⁺ state. The calculated E1 transition probability from the 9/2⁺ state has been used as a probe in suggesting the following main components for the lowest-lying 7/2^- state: 7/2 5/2^-[523] in ¹⁴⁹Nd, 7/2 3/2^-[521] in ¹⁵³Gd and 7/2 3/2^-[521] in ¹⁵⁵Dy. The corresponding 7/2^- state in ¹⁵¹Sm is proposed to be 7/2{1}3/2^-[532] + 5/2^-[523]{1}. All calculations have been performed using a particle-rotor model with a nonspheroidal Woods-Saxon potential.