Showing papers in "Journal of Physics G: Nuclear Physics in 1979"
TL;DR: The Weinberg-Salam theory was reformulated as a pure Yang-Mills theory in a six-dimensional space, the Higgs field being interpreted as gauge potentials in the additional dimensions as discussed by the authors.
Abstract: The Weinberg-Salam theory is reformulated as a pure Yang-Mills theory in a six-dimensional space, the Higgs field being interpreted as gauge potentials in the additional dimensions. Viewed in this way, the condition that the Higgs field transforms as a U(1) representation of charge one is equivalent to requiring a value of 30 degrees for the Weinberg angle. A second consistent determination comes form the idea borrowed from monopole theory that the electromagnetic field is the direction of the Higgs field.
136 citations
TL;DR: In this article, a new method of calculating nuclear charge and matter distributions is described, which uses the sum of the squares of single-particle wavefunctions to give a first approximation and then iterates the proton and neutron densities in a formalism that takes into account the interaction between these densities and between the valence and core nucleons.
Abstract: A new method of calculating nuclear charge and matter distributions is described. It uses the sum of the squares of single-particle wavefunctions to give a first approximation and then iterates the proton and neutron densities in a formalism that takes into account the interaction between these densities and between the valence and core nucleons. The single-particle potentials are adjusted to give the experimental centroid separation energies and configuration mixing is included using shell-model occupation probabilities. The method is applied to the core nuclei 16O and 40Ca, to their isotopes and to other nuclei in the sd and pf shells. Detailed comparisons are made with all available experimental data on nuclear charge and matter distributions.
85 citations
TL;DR: The results of a series of lowest-order constrained variational calculations for various nucleon fluids are presented in this article, which allow in a self-consistent fashion for the explicit excitation of a nucleon into an N*(1234) state via a recent transition potential proposed by Green, Niskanen and Sainio.
Abstract: The results of a series of lowest-order constrained variational calculations for various nucleon fluids are presented. The calculations are based upon the Reid soft-core potential (1968) and allow in a self-consistent fashion for the explicit excitation of a nucleon into an N*(1234) state via a recent transition potential proposed by Green, Niskanen and Sainio (1978). For nuclear matter a binding energy of 16 MeV per nucleon is obtained at a saturation density 0.25 N fm-3. The compressibility of nuclear matter is calculated to be 300 MeV. From a study of asymmetric matter a symmetry coefficient of 33 MeV is obtained. It is found that the inclusion of N*'s in beta-stable matter leads to a suppression of the proton abundance at high densities.
73 citations
TL;DR: In this article, it was shown that in chiral-invariant vector-gluon theories, the spontaneous generation of fermion mass is associated with zero-mass pseudoscalar bosons.
Abstract: A proof is given of the theorem that, in chiral-invariant vector-gluon theories, the spontaneous generation of fermion mass is associated with zero-mass pseudoscalar bosons. The proof relies heavily on the proper determination of Bethe-Salpeter kernels which respect the Ward identities correctly, and is exact to the extent that the propagator is self-consistently truncated. Given this result, we survey the implications of PCAC for the quark-gluon model.
70 citations
TL;DR: In this paper, the authors reproduce single-particle level spins and parities of odd-A nuclei by adjusting the strength parameter lambda and the radius parameter (r0)so of the spin-orbit part of the deformed Woods-Saxon potential.
Abstract: The authors aim to reproduce single-particle level spins and parities of odd-A nuclei by adjusting the strength parameter lambda and the radius parameter (r0)so of the spin-orbit part of the deformed Woods-Saxon potential. Discussion is concentrated on the A>or=210 nuclei for which comparison with the extracted experimental level spacing is done. In addition, parametrisation of the deformed Woods-Saxon potential is discussed for A=40-110 nuclei (the nuclei with 110
70 citations
TL;DR: The experimental half-lives for alpha decay of Ra, Th, U, Pu, Cm, Cf, Fm and No even-even isotopes are well reproduced in this article.
Abstract: Alpha decay is considered to be a very asymmetric fission process with fragments of different charge densities. Q-values and half-lives are computed in the two-centre parametrisation by using the liquid-drop-model generalisation replacing the surface energy by a folded Yukawa plus exponential potential. An empirical shell correction is introduced to obtain the experimental Q values exactly. The experimental half-lives for alpha decay of Ra, Th, U, Pu, Cm, Cf, Fm and No even-even isotopes are well reproduced.
57 citations
TL;DR: In this article, two-body correlation functions obtained in a LOCV calculation on nuclear matter using the Reid soft-core potential are state averaged and then used to calculate the three-body convergence parameter kappa 3 and three body cluster energy E3.
Abstract: Two-body correlation functions obtained in a LOCV calculation on nuclear matter using the Reid soft-core potential are state averaged and then used to calculate the three-body convergence parameter kappa 3 and three-body cluster energy E3. kappa 3 is found to be less than 0.1 for Fermi momenta kF
54 citations
TL;DR: In this paper, an improved set of imaginary components for the T = 1 nucleon-nucleon phase-shifts is obtained by means of a model involving the Delta (1236).
Abstract: By means of a model involving the Delta (1236), an improved set of imaginary components for the T=1 nucleon-nucleon phase-shifts is obtained. These phase-shifts are then used to calculate inelastic nucleon-nucleon cross sections below 720 MeV, including the spin-dependent inelastic cross sections Delta sigma Ti and Delta sigma Li.
36 citations
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TL;DR: In this paper, the vector gluon propagator of quantum chromodynamics was investigated by means of the gauge technique, which provided a self-consistency equation for the propagator from which one may recover the asymptotic freedom behaviour p2 Delta to (1+ gamma ln(-p2/ mu 2))-1 in the ultraviolet regime p2>> mu 2.
Abstract: The vector gluon propagator of quantum chromodynamics is investigated by means of the gauge technique. The technique provides a self-consistency equation for the propagator from which one may recover the asymptotic freedom behaviour p2 Delta to (1+ gamma ln(-p2/ mu 2))-1 in the ultraviolet regime p2>> mu 2. The corresponding behaviour in the infrared limit p2<< mu 2 is found to be p2 Delta approximately (1n(-p2/ mu 2))-2.
36 citations
TL;DR: In this article, a systematic study of proton scattering from 16O and 40Ca at a wide range of energies, as well as 58Ni and 56Fe, is presented.
Abstract: An earlier suggestion of the authors (1976) that the proton optical-model potential has terms, both real and imaginary, which depend explicitly on angular momentum is hereby supported by a systematic study of proton scattering from 16O and 40Ca at a wide range of energies, as well as 58Ni and 56Fe. Not only are the fits to data improved (in some cases the improvement is very great), but the extracted parameters show certain striking regularities which were less apparent in l-independent fits. We also make some general remarks concerning the status of phenomenological fits and the interpretation of l dependence.
32 citations
TL;DR: In this paper, cross sections of (n, 2n) reactions of 13-18 MeV neutrons with 232Th and 238U were measured using activation techniques and the excitation functions were compared with statistical-model calculations including pre-equilibrium nucleon emission.
Abstract: Cross sections of the (n,2n) reactions of 13-18 MeV neutrons with 232Th and 238U have been measured using activation techniques. The excitation functions are compared with statistical-model calculations including pre-equilibrium nucleon emission. At 18 MeV the (n,2n) reactions predominantly start prior to equilibration.
TL;DR: In this paper, the space and time evolution of the compressed zone formed in head-on collisions of two nuclei is investigated and the maximum compressions achieved turn out to be not very different from those following from hydrodynamic estimations.
Abstract: On the basis of a relativistic intranuclear cascade model which reproduces the bulk of experimental data, the space and time evolution of the compressed zone formed in head-on collisions of two nuclei is investigated. The maximum compressions achieved turn out to be not very different from those following from hydrodynamic estimations. The shape of the spatial distribution of the compressed zone is not that of a classical Mach cone. The existence of a rarefied zone resulting in an effect of the 'dead-water' type is found. The characteristics of pions emerging from collisions of nuclei at relativistic energies are discussed.
TL;DR: The angular distribution and linear polarisation of gamma rays from the alpha,n gamma reactions on 126Te and 128Te at a beam energy of 16 MeV have been measured in order to obtain information on the low-lying positive-parity levels of 129Xe and 131Xe as discussed by the authors.
Abstract: The angular distributions and linear polarisations of gamma rays from the ( alpha ,n gamma ) reactions on 126Te and 128Te at a beam energy of 16 MeV have been measured in order to obtain information on the low-lying positive-parity levels of 129Xe and 131Xe. Spin and parity assignments of 3/2+, 5/2+, 7/2+, 7/2+ and 5/2+ have been made to levels in 129Xe at Ex=318.2, 321.7, 518.7, 665.0 and 822.1 keV respectively and of 5/2+ and 7/2+ to levels in 131Xe at 364.5 and 636.9 keV respectively. Several mixing ratios have been determined, allowing electromagnetic transition strengths to be deduced for a number of the decay transitions. The results have been discussed with reference to available calculations using the particle-vibration coupling model. This comparison has shown up a number of failures in the detailed predictions of the model. Some of these may be removed by considering the cluster structure of the particle configurations.
Abstract: A simple energy-dependent optical potential is obtained which describes proton scattering from light nuclei in the energy range 50-160 MeV. The properties of the potential are compared with other available phenomenological potentials and with theoretical predictions. Some distorted-wave calculations for the (p, 2p) reaction are included to show the sensitivity to the choice of optical potential.
TL;DR: In this paper, the importance of the photoproduction of pions as a source of low-energy muons in cosmic-ray air showers of the highest energy is examined.
Abstract: The authors examine the importance of the photoproduction of pions as a source of low-energy muons in cosmic-ray air showers of the highest energy. Results of detailed calculations of the characteristics of this additional muon component are presented. The consequences for the interpretation of experiments which are sensitive to low-energy muons in high-energy extensive air showers such as existing experiments to measure muon core angles, shower particle arrival times and the primary energy spectrum are discussed.
TL;DR: Isomer ratios have been measured in Sb and Te isotopes prepared in the 115In( alpha,n), 115In ( alpha,3n), 118,120,122,124Sn( alpha,pn), and 120Sn(alpha,3n) reactions, using a range of bombarding energies between 16.6 and 38.4 MeV as mentioned in this paper.
Abstract: Isomer ratios have been measured in Sb and Te isotopes prepared in the 115In( alpha ,n), 115In( alpha ,3n), 118,120,122,124Sn( alpha ,pn), and 120Sn( alpha ,3n) reactions, using a range of bombarding energies between 16.6 and 38.4 MeV. In most of the product nuclei the isomer ratios are smaller than the predictions of the sharp cut-off model, showing that the isomer is less than 100% efficient in trapping high-spin products. The variation of isomer ratio with bombarding energy is described by a simple expression for the trapping efficiency.
TL;DR: Cross sections of the 42Ca (p, gamma )43Sc, 42Ca( alpha ,n)45Ti and 44Ca(p,n)44Sc reactions have been measured by detection of 0.511 MeV gamma rays in coincidence from positron decay of the product nuclei.
Abstract: Cross sections of the 42Ca(p, gamma )43Sc, 42Ca( alpha ,n)45Ti and 44Ca(p,n)44Sc reactions have been measured by detection of 0.511 MeV gamma rays in coincidence from positron decay of the product nuclei. The 44Ca(p,n) cross section is a factor three larger than a previous measurement. The magnitude of the 42Ca(p, gamma ) cross section above E=4.5 MeV is very sensitive to the magnitude of the 44Ca(p,n) cross section due to a 0.56%44Ca component in the 42Ca targets, since 44Sc and 43Sc have virtually the same half-life. Reasonable values for the (p, gamma ) cross section are obtained using the present (p,n) cross section measurement. The 42Ca( alpha ,n)45Ti cross section has not been reported previously. All cross sections are compared with a statistical model calculation.
TL;DR: In this article, the surface thickness of nuclear densities and single-particle potentials calculated self-consistently in the energy-density formalism was studied for a set of nuclei near the stability line.
Abstract: The surface thickness of nuclear densities and single-particle potentials calculated self-consistently in the energy-density formalism is studied for a set of nuclei near the stability line. The surface is divided into an internal part (inside the half-density radius) and an external part (outside the half-density radius). The variations of the thickness of these two parts with the nucleon number are examined. Shell effects and differences between the two parts are studied.
TL;DR: In this paper, the authors show how the Hamiltonian depends on the definition of an optimal body-fixed frame and how to obtain the best possible decoupling of internal motion and collective rotation.
Abstract: Basic to an approach to the problem of collective rotations is the definition of an optimal body-fixed frame. By a clear and elegant method for the transformation to collective and internal coordinates the authors show how the Hamiltonian depends on the definition of this frame. These results are used to obtain the best possible decoupling of internal motion and collective rotation, the so called specific decoupling. The corresponding equations are obtained by perturbation treatment in terms of the total angular momentum. This is shown to be equivalent to an extremum principle where the definition of the internal frame is varied. The extremum principle proves to be more powerful than the perturbational method so that the concept can be applied to deformed nuclei with realistic interactions and also to higher spins. This will be reported in the following papers.
TL;DR: In this paper, the sign changes in delta arise from a sign change in the M1 matrix element and the sources of such a change are discussed, and the results are compared with the predictions of the dynamic deformation theory.
Abstract: Changes occur in both the sign and magnitude of E2:M1 multipole mixing ratios for different types of transition upon crossing from 'spherical vibrational' (N or=90) nuclei. Experimental results are compared with the predictions of the dynamic deformation theory. The sign changes in delta arise from a sign change in the M1 matrix element. The sources of such a change are discussed.
TL;DR: In this paper, the energies and relative intensities of the primary gamma rays from the 44Sm(n, gamma )145Sm reaction have been measured with a Ge(Li) pair-formation gamma-ray spectrometer from 3.0-7.2 MeV.
Abstract: The energies and relative intensities of the primary gamma rays from the 44Sm(n, gamma )145Sm reaction have been measured with a Ge(Li) pair-formation gamma -ray spectrometer from 3.0-7.2 MeV. The neutron separation energy of 145Sm was found to be 6757.1+or-0.3 keV. A comparison of the measured strengths of excitation of levels in 145Sm in the (n, gamma ) and (d,p) reactions reveals that they are strongly correlated. These results are discussed in terms of a number of simple neutron-capture reaction mechanisms.
TL;DR: In this article, a level scheme based on excitation functions, on angular distributions and on prompt and delayed gamma- gamma coincidence measurements is proposed and compared with findings by other authors.
Abstract: Gamma rays from levels in 151Eu have been studied following the 152Sm (p,2n) reaction. A level scheme based on excitation functions, on angular distributions and on prompt and delayed gamma - gamma coincidence measurements is proposed and compared with findings by other authors. Some transitions observed lead to levels not previously compared with findings by other authors. Some transitions observed lead to levels not previously identified in gamma -ray work. The experimental results are compared with the predictions of the rigid rotor-plus-particle model including Coriolis coupling. Negative-parity states are described in terms of the interacting-boson model.
TL;DR: In this article, the repulsive Coulomb interaction is included in the integral-equation approach to two-particle scattering, and the partial-wave projected momentum-space Coulomb wavefunctions are studied and their application is discussed.
Abstract: The repulsive Coulomb interaction is included in the integral-equation approach to two-particle scattering. The partial-wave projected momentum-space Coulomb wavefunctions are studied and their application is discussed. Practical examples for their successful use (i) in determining scattering parameters from a given potential and (ii) in the inverse scattering theory are given.
TL;DR: In this article, the dependence on the z projections of the angular momenta of the particle separated out as a multiplicative constant was investigated and a simplified form of the transfer amplitude was used to obtain an analytic expression for angular distributions.
Abstract: Semiclassical conditions appropriate to a grazing collision have been used to study the dependence of the transfer amplitude on the distance of closest approach, d, for direct reactions. It is found to fall off exponentially with increasing d, the decay constant being a function of the initial and final binding energies of the transferred particle. The dependence on the z projections of the angular momenta of the particle separates out as a multiplicative constant. This simplified form of the transfer amplitude is used to obtain an analytic expression for angular distributions. Comparison is made with experiment for the reaction 26Mg(11B,10B)27Mg at 114 MeV laboratory energy.
TL;DR: In this paper, a simple effective interaction consisting of a density-dependent delta-function repulsion and a gaussian attraction was derived for the single-particle potential, symmetry coefficient, effective mass and other related quantities in nuclear matter.
Abstract: The single-particle potential, its isotopic spin dependence, symmetry coefficient and effective mass in nuclear matter have been calculated using a simple effective interaction consisting of a density-dependent delta-function repulsion and a gaussian attraction. The density dependence in the interaction has been considered in three different forms: rho 2/3, rho 1/3 and rho 1/6. The three parameters of the interaction are determined so as to reproduce the correct binding energy and density in nuclear matter and the ground-state energy of 16O. With the above interaction, simple relations for the single-particle potential, symmetry coefficient, effective mass and other related quantities in nuclear matter are derived. It is found that the Hugenholtz-Van Hove theorem is satisfied exactly and the results for these quantities are in good agreement with those referred to in the literature.
TL;DR: In this paper, a Ge(Li)-Na(Tl) escape-suppressed spectrometer and a three-Ge(Li) Compton polarimeter were used to measure the angular distribution and linear polarisation of gamma rays at alpha bombarding energies of 7.0, 14.5 and 17 MeV.
Abstract: The reaction 40Ar( alpha ,n gamma )43Ca was used to populate the levels in 43Ca at bombarding energies between 5.5 and 19 MeV, gamma - gamma coincidence measurements at Ealpha =8.5, 15 and 16 MeV being used to establish the decay scheme of 53 levels. Several new levels and new decays of levels with high angular momentum were established. The Doppler-shift attenuation method was used with solid Ar targets to deduce the mean lifetimes for most of these levels. A Ge(Li)-Na(Tl) escape-suppressed spectrometer and a three-Ge(Li) Compton polarimeter were used to measure the angular distribution and linear polarisation of gamma rays at alpha bombarding energies of 7.0, 14.5 and 17 MeV.
TL;DR: An extension of the folded Yukawa potential, surface and Coulomb energies formulae for the fusion of heavy ions (or fission fragments) with different charge-to-mass ratio is presented in this paper.
Abstract: An extension of the folded Yukawa potential, surface and Coulomb energies formulae for the fusion of heavy ions (or fission fragments) with different charge-to-mass ratio is presented. One also has to add the volume contribution to the deformation energy. For various combinations of nuclei along the Green approximation of the line of beta stability, the general trends in the variation of interaction barriers, fusion Q values and fission barriers are studied, showing that errors of the order of some tens of MeV could appear if the difference between charge densities is ignored. Calculated interaction barriers are in good agreement with available experimental data for some 58 pairs of colliding nuclei. PES for the reactions 109Ag+40Ar, 84Kr+65Cu, 75As+74Ge, 138Ce+57Fe, 144Nd+61Ni, 116Cd+84Kr and 142Nd+84Kr are computed using the parametrisation of the asymmetric spheroid with neck. The relative values of the saddle-point energies for a real system and for a charge-equilibrated one show how important this effect could be in the entrance channel of a fusion reaction.
TL;DR: In this article, a simple application of old-fashioned final-state-interaction theory is shown to give the result that rescattering in the deck model of diffraction dissociation is well represented by multiplying the bare amplitude by ei delta cos delta.
Abstract: A simple application of old-fashioned final-state-interaction theory is shown to give the result that rescattering in the Deck model of diffraction dissociation is well represented by multiplying the bare amplitude by ei delta cos delta . The physical reasons for this result emerge particularly clearly in this formulation.
TL;DR: In this paper, the virtual photon intensities for electron-scattering reactions were calculated using the plane-wave Born approximation and the generalised Helm model to describe the nuclear transition charge and current densities.
Abstract: Virtual photon intensities for electron-scattering reactions are calculated using the plane-wave Born approximation and the generalised Helm model to describe the nuclear transition charge and current densities
TL;DR: In this paper, the physical meaning of the phenomenological l-dependent terms previously found to be necessary to give good fits to a wide range of proton elastic scattering data is discussed, and the effects of these terms on the real and imaginary parts of the s matrix are strikingly similar to the effects due to the coupling of pick-up channels.
Abstract: The authors discuss the physical meaning of the phenomenological l-dependent terms previously found to be necessary to give good fits to a wide range of proton elastic scattering data. They demonstrate that the effects of these terms on the real and imaginary parts of the s matrix are strikingly similar to the effects due to the coupling of pick-up channels. They identify the separate effects of the real and imaginary l-dependent components. Some general interpretations of anomalies revealed by l-dependent analyses are discussed, but further experiments are required to give a full account of these.