Angular momentum projected Hartree-Fock-Theory

The Euler Lagrange equations corresponding to the Hartree-Fock variational problem after angular momentum projection (PHF) are derived. The exact equations are simplified employing the Gaussian overlap approximation. The solution of the PHF equations in this approximation is seen to be not much more complicated than the solution of the normal HF problem.     

Angular momentum of fission fragments

We continue the discussion on the respective roles of individual and collective motion in the angular momentum distribution in fission fragments. As in our prior publications on the subject, the role of individual nucleon motion in fragments in the postscission configuration is underlined, and the central part in the discussion concerns phenomena observed in the spontaneous fission of even-even nuclei. A formalism is prepared to study the spin distribution of fragments in induced fission from high-spin states.     

Angular correlations in proton-proton collisions producing a high transverse momentum π0

In an experiment at the CERN ISR, a streamer chamber detector surrounding one of the intersection regions was triggered on large transverse momentum π⁰'s by means of an array of lead-glass counters. The directions of charged particles and γ rays converted in lead-oxide plates inside the streamer chamber were measured. Data were taken at c.m. energy of √s = 53 GeV at two production angles of the high p_Tπ⁰ (90° and 53°). They indicate an enhancement of particles mostly in the hemisphere opposite to the π⁰. In the 53° data, a shift of this enhancement towards rapidities opposite to the rapidity of the π⁰ and confined to a ±30° azimuthal region around the collision plane is observed. In addition, a short-range angular correlation is evidenced between the high p_Tπ⁰ and the other collisions products (photons or charged particles). Two-particle correlations between charged particles produced in association with the high p_Tπ⁰ are found similar to those     

Angular momentum population in fragmentation reactions

Using a relativistic transport model followed by a statistical sequential binary emission model, the population of metastable high-spin isomeric states are studied in relativistic projectile fragmentation reactions. The initial angular momentum distribution are generated from hole excitations. We find that the angular momentum distribution of the excited prefragments are considerably broadened due to light particle evaporation. The model reproduces the experimentally measured population of relatively low-lying states and underpredicts states with high angular momentum I?17?$I?17?$. We propose that coupling the spin of the excited and hole states in the prefragment will give a better understanding of the data.     

Angular momentum in peripheral fragmentation reactions

The angular momentum induced in peripheral fragmentation reactions at relativistic energies is described on the basis of shell-model considerations. An analytical expression for the spincutoff parameter of prefragments is obtained, and numerical calculations in the framework of the abrasion-ablation model are performed in order to estimate the angular-momentum distribution of prefragments and final fragments. Additionally, an approximative formula is given to calculate the angular-momentum distribution of final fragments.     

Angular momentum transfer in incomplete fusion

Isomeric cross-section ratios of evaporation residues formed in¹²C+⁹³Nb and¹⁶O+⁸⁹Y reactions were measured by recoil catcher technique followed by off-line γ-ray spectrometry in the beam energy range of 55.7–77.5 MeV for¹²C and 68–81 MeV for¹⁶O. The isomeric cross-section ratios were resolved into that for complete and incomplete fusion reactions. The angular momentum of the intermediate nucleus formed in incomplete fusion was deduced from the isomeric cross-section ratio by considering the statistical deexcitation of the incompletely fused composite nucleus. The data show that incomplete fusion is associated with angular momenta slightly smaller than critical angular momentum for complete fusion, indicating the deeper interpenetration of projectile and target nuclei than that in peripheral collisions.     

Angular correlations in nuclear fission

Interference effects in the angular distributions of products originating from binary and ternary nuclear fission induced by slow neutrons are reviewed.     

Angular correlations in pair creation

We present the Monte Carlo analysis of angular correlations in electron-positron pair production by the laser field-heavy ions impact process. It is shown that, for linearly polarized laser fields, pairs are created mainly in the plane spanned by the polarization vector and the laser photon momentum, and that the angular distribution of created electrons and positrons is anticorrelated.     

Angular distribution of parametric X-rays

Results of the first experimental observation of the angular distribution of parametric X-rays within the diffraction peak are described. These results are compared with theoretical calculations and are of great importance for an unequivocal identification of the new mechanism of X-ray production by ultrarelativistic charged particles in a crystal.     

Angular momentum of gaussian light beams

Analysis of the orbital angular momentum of paraxial light beams shows that a key role in the formation of this quantity is played by phase relations between longitudinal and transverse radiation fields. When a light beam is circularly polarized or has a helical wave front, the azimuthal component of the Poynting vector and the density of orbital angular momentum prove to be non-zero. In the case of circularly polarized radiation, the azimuthal component of the Poynting vector and the density of the orbital angular momentum can change the sign at different points in the cross section of the light beam, while the total orbital momentum of the beam remains quantized.     

Angular momentum of a brane-world model

In this paper we discuss the properties of the general covariant angular momentum of a fivedimensional brane-world model. Through calculating the total angular momentum of this model, we are able to analyze the properties of the total angular momentum in the inflationary RS model. We show that the space-like components of the total angular momentum of the inflationary RS model are all zero while the others are non-zero, which agrees with the results from ordinary RS model.     

Angular momentum of a brane-world model

In this paper we discuss the properties of the general covariant angular momentum of a five-dimensional brane-world model. Through calculating the total angular momentum of this model, we are able to analyze the properties of the total angular momentum in the inflationary RS model. We show that the space-like components of the total angular momentum of the inflationary RS model are all zero while the others are non-zero, which agrees with the results from ordinary RS model.     

Angular momentum non-conserving decays in isotropic media

Various processes that are forbidden in vacuum due to angular momentum conservation can occur in a medium that is isotropic and does not carry any angular momentum. We illustrate this by considering explicitly two examples. The first one is the decay of a spin-0 particle into a photon and another spin-0 particle, using a model involving the Yukawa interactions of the scalar particles with a charged fermion field. The second one involves the decay of a neutrino into another neutrino and a graviton, in the standard model of particle interactions augmented with the linearized gravitational couplings.     

Angular momentum coupling in heavy-ion transfer reactions

A general expansion of the distorted wave transition amplitude for heavy-ion transfer reactions into terms with definite recoil orbital angular momentum transfer is given and discussed. It is shown that recoil effects tend to be enhanced when the surface localization of the reaction is not favoured by kinematical conditions.     

Angular momentum polarization in molecular collisions : Classical and quantum theory for measurements using resonance fluorescence

Inelastic or reactive collisions typically produce an anisotropic distribution of rotational angular momentum. An explicit and general treatment is given for the intensity and polarization of resonance fluorescence from molecules produced in such processes. Both classical and quantum results are expressed in terms of bipolar harmonics and state multipoles formed from linear combinations of density matrix elements. The treatment provides an inversion procedure for determining moments of the rotational angular momentum distribution ; twelve independent moments can be obtained. The combinations of angular momentum operators involved are even in eight of these moments and odd in four, with respect to reflection in a plane containing the initial and final relative velocity vectors. Measurements of the even moments require linearly polarized excitation and fluorescence, whereas measurements of the odd moments require circularly polarized excitation. The requisite experimental geometry and other practical aspects are discussed. In the three appendices are discussed the classical limits of transition intensities, a density matrix treatment of atom-rigid-rotor collisions, including analysis of state multipole symmetries ; and the coupling coefficients for parallel angular momenta.     

Angular momentum reduction in the four-body problem

A complete angular momentum analysis of the integral equations of motion for four identical spinless particles is given. After separation of the variables associated with rotation, the equations of motion take the form of an infinite set of coupled integral equations in three continuous variables. In general, the four-particle kinematic factors in the integral kernels are expressed as bilinear combinations of factors of the three-particle kinematic factors type. For the case of a separable two-particle interaction the equations obtained are simplified so that they are reduced to coupled integral equations in two continuous variables.     

Four-photon correlations in parametric down-conversion

Four-photon correlations of the output radiation of a parametric amplifier with a vacuum at the input are considered for an arbitrary parametric gain coefficient. Such states are interpreted in the literature as four-photon states. It is shown that the fourth-order correlation function for such states in the limit of a small number of photons has an asymptotics typical of two-photon states. Nevertheless, even in the “classical” limit of high intensities, the level of four-photon correlations, i.e., the value of the normalized fourth-order correlation function, is substantially greater than that for coherent and even thermal fields.