123154942
Elastic and inelastic scattering of alpha particles from Ca-40, Ca-44 over a broad range of energies and angles
Angular distributions for alpha -particle elastic scattering by /sup 40,44/Ca and excitation of the 3.73 MeV 3/sup -/ collective state of /sup 40/Ca were measured for incident energies ranging from 40 to 62 MeV. An extensive optical model analysis of these elastic scattering cross sections and other available data, using squared Woods-Saxon form factors, results in potentials with fixed geometry for both real and imaginary parts and depths with smooth energy behavior over a broad incident energy range. These results are discussed in the frame of the semi-classical approximation developed by Brink and Takigawa (1977). The sensitiveness of the calculated elastic scattering cross sections to the real part of the potentials as a function of the projectile-target distance has been investigated by means of a notch test. Distorted-wave Born-approximation calculations for the excitation of the 3.73 MeV 3/sup -/ state of /sup 40/Ca are presented.
59128830
The ALPS Project: Open Source Software for Strongly Correlated Systems
We present the ALPS (Algorithms and Libraries for Physics Simulations) project, an international open source software project to develop libraries and application programs for the simulation of strongly correlated quantum lattice models such as quantum magnets, lattice bosons, and strongly correlated fermion systems. Development is centered on common XML and binary data formats, on libraries to simplify and speed up code development, and on full-featured simulation programs. The programs enable non-experts to start carrying out numerical simulations by providing basic implementations of the important algorithms for quantum lattice models: classical and quantum Monte Carlo (QMC) using non-local updates, extended ensemble simulations, exact and full diagonalization (ED), as well as the density matrix renormalization group (DMRG). The software is available from our web server at http://alps.comp-phys.org/.
119969931
Optical-model Description of Alpha+o-16 Elastic-scattering and Alpha-cluster Structure in Ne-20
O16(,) elastic scattering angular distributions have been measured for incident energies 39.3, 49.5, and 69.5 MeV. These data, and previous measurements at 32.2, 104, and 146 MeV, have been subjected to a global optical model analysis. The deduced global potential has two energy-dependent parameters which are found to vary smoothly with energy and it is uniquely determined by the data. Backward angular distributions measured between 40 and 54 MeV are also presented and shown to be nicely reproduced by the model. The sensitivity of the cross sections to the various regions of the real potential has been investigated as a function of energy using the notch test technique. The low energy behavior of the differential cross sections can be understood in terms of the semiclassical decomposition of Brink and Takigawa. A natural extrapolation of the global potential below 30 MeV is shown to reproduce the wide bump observed in the experimental excitation functions around 20 MeV. This bump is shown to be due to an l=8 shape resonance and is interpreted as the J=8+ member of the K=04+ rotational band of Ne20, in contradiction with the current attribution. Other bound and quasibound states supported by the potential are discussed in the light of orthogonality condition model-type arguments and shown to be consistent with the well-known K=01+ and 0- bands, and with the first three states of the K=04+ band of Ne20. NUCLEAR REACTIONS O16(,), measured (), E=39.3, 49.5, 69.5 MeV; global optical model analysis, E=32-146 MeV; semiclassical decomposition of the scattering amplitude; investigation of the compatibility of the potential description with existing low energy data and comparison with cluster models. © 1983 The American Physical Society.
34169460
Luneburg lens approach to nuclear rainbow scattering.
The physical interpretation of nuclear rainbow scattering within the frame of the optical model is critically investigated. Starting from the properties of the Luneburg lens, a gradient index device that displays refractive features similar to those of the nuclear potential, important differences between the mechanisms producing the nuclear and optical rainbows are pointed out.
123123854
Evidence for alpha-particle clustering in the Ti44 nucleus
The ..cap alpha..-particle cluster structure of /sup 44/Ti, which is of considerable interest for investigation of the persistence of ..cap alpha.. clustering in the region of the sd-shell closure, is studied within the frame of a local-potential approach. It is shown that the model leads to specific predictions if continuity with existing unique ..cap alpha..+ /sup 40/Ca optical potentials is insisted upon; in particular, the existence of an as yet experimentally unknown ..cap alpha..-cluster negative-parity band, starting just above the ..cap alpha..+ /sup 40/Ca threshold, is strongly suggested.
123108693
Connection of Kukulin's nucleon-nucleon deep potential with realistic repulsive core interactions
The on-shell equivalence of the deep quantum-chromodynamically motivated realistic nucleon-nucleon interaction recently proposed by Kukulin et al. with more conventional repulsive-core forces is investigated by eliminating its unphysical deeply bound states, while preserving its scattering properties and the binding energy of the deuteron. The resulting interaction, which is built both in the singlet and triplet channels, displays ar−2 singular repulsive core followed by a shallow attraction of intermediate range, in good semiquantitative agreement with existing realistic nucleon-nucleon interactions.
123629832
Intense Coherent Submillimeter Radiation in Electron Storage Rings
Energetic electron bunches in storage rings produce pulsed bursts of incoherent synchrotron radiation. It is pointed out that they should also produce a roughly comparable power output of coherent radio-frequency radiation. Thus electron storage rings, in addition to their intended purpose and their secondary use as intense sources of x rays, might additionally serve as pulsar simulators, producing a similar spectrum of coherent emission, the properties and modification of which could be studied in the laboratory. A spontaneous bunching of electrons (artificially bunched here) might be evidenced as ''superbunching.''
120405009
NEUTRAL WEAK INTERACTION CURRENTS
119697750
Gravitationally induced electric fields in conductors.
An estimate for the gravitationally induced electric field is presented that is based on a statistical model for the electrons in a metal in which their long-range electrostatic interaction with a differentially compressed lattice of positive ions is taken into account. The field is in the upward direction and is estimated to be of the order of magnitude $E\ensuremath{\approx}\frac{\mathrm{Mg}}{e}$, where $M$ is the atomic mass, $e$ is the electronic charge, and $g$ is the acceleration due to gravity. For copper, $E\ensuremath{\approx}{10}^{\ensuremath{-}7}$ V/m. An earlier estimate by Schiff and Barnhill gives a field in the downward direction equal to $\frac{\mathrm{mg}}{e}$, where $m$ is the mass of the electron. The difference between our result and theirs is due to different treatments of the effect of lattice compressibility.
118496663
Gravitating superconducting strings with timelike or spacelike currents
We construct gravitating superconducting string solutions of the $U(1{)}_{\mathrm{local}}\ifmmode\times\else\texttimes\fi{}U(1{)}_{\mathrm{global}}$ model by solving the coupled system of Einstein and matter field equations numerically. We study the properties of these solutions in dependence on the symmetry breaking to Planck mass ratio. Using the macroscopic stability conditions formulated by Carter, we observe that the coupling to gravity allows for a new stable region that is not present in the flat space-time limit. We match the asymptotic metric to the Kasner metric and show that the relations between the Kasner coefficients and the energy per unit length and tension suggested previously are well fulfilled for symmetry breaking scale much smaller than the Planck mass. We also study the solutions to the geodesic equation in this space-time. While geodesics in the exterior space-time of standard cosmic strings are just straight lines, test particles experience a force in a general Kasner space-time, and as such, bound orbits are possible.
121467224
PARITY NONCONSERVATION IN NUCLEI
BS>The influence of the known weak interactions on the parity of nuclear states is discussed. Derivation of a parity nonconserving interaction rests on the assumption of a current-current hypothesis for the weak interactions. Consequently, observation of parity impurity effects would be an important confirmation of this hypothesis. A simple approximate method of treating the nuclear parity impurity is developed and applied in an effort to find experimental situations favorable to observation of effects due to such impurity. Parity-forbidden alpha decay from excited states of light nuclei and certain electromagnetic transitions in the heavy nuclei appear to be promising. Special attention was paid to the internal conversion electrons from the 123kev transition nn Lu/sup 173/ whose polarization is estimated to be about 0.4%. An effect on polarized neutrons analogous to optical rotation is also discussed. (auth)