Light scattering from fluids. A semi-phenomenological calculation of the coupling constants between the orientational and translational motion

The coupling parameters X and Z between translational and orientational motions, which determine the lineshapes of the VH and HH depolarized light scattering spectra respectively, are calculated. By using a simple model that explains the connection between rotational and translational motions, it is shown that X and Z are proportional to k²η_r/ρ. The correct order of magnitude of the proportionality coefficient is obtained.     

Absolute scattering cross-section measurements by a ratio technique

Calculations and measurements are presented which show that absolute scattering cross sections (“Rayleigh ratios”) can be determined by measuring the ratio of the depolarized intensity of doubly scattered light to the polarized intensity of singly scattered light. This technique should be useful in determining the susceptibilities of fluids and the molecular weights of macromolecules.     

Light scattering in a layer of correlatively arranged optically soft particles

The light scattering by an ensemble of monodisperse spatially correlated optically soft spherical particles is studied in the interference approximation. A model of the interaction of particles is proposed in which the spatial correlation between particles is determined by a radius R _c exceeding the particle radius R _p. The radial distribution function is calculated in the Percus-Yevick approximation for hard spheres of the radius R _c. To simulate the radiation scattering from an individual particle of the radius R _p, the Mie equations are used. It is shown that, in a medium of correlated small nonabsorbing particles of the radius R _c > R _p, an abnormal wavelength dependence of the refractive index is possible at a low volume concentration of particles. The results obtained explain some experimentally observed features of the scattering in sodium borosilicate glasses with a small concentration of scattering centers.     

New effects in low energy scattering of pµ atoms

Strong solid state effects in low energy scattering of pμ atoms in solid hydrogen are reported and analyzed. Such effects have been observed in TRIUMF experiment E742 where muons are stopped in thin frozen (3 K) layers of hydrogen. Emission of low energy pμ atoms from the hydrogen layer into adjacent vacuum was much higher than expected, based on calculations which ignored the solid nature of hydrogen. Monte Carlo simulations, performed using the scattering cross-sections with solid state effects taken into account, show the important role of the coherent elastic Bragg scattering in the diffusion of pμ atoms. For pμ energies lower than the Bragg cut-off limit (∼2 meV) the total scattering cross-section falls by several orders of magnitude, the hydrogen target becomes transparent and the emission of cold pμ atoms takes place. This revised version was published online in August 2006 with corrections to the Cover Date.     

Elastic and inelastic scattering of 800-MeV protons on <Superscript>16</Superscript>O and <Superscript>20</Superscript>Ne nuclei

Differential cross sections and polarization observables for the elastic and inelastic scattering of 800-MeV protons on ¹⁶O and ²⁰Ne nuclei are calculated on the basis of the theory of multiple diffractive scattering and the α-cluster model involving dispersion. The single-particle nucleon-density distributions obtained within the α-cluster model involving dispersion are used in the calculations. The differential cross sections and polarization calculated for elastic and inelastic p¹⁶O and p²⁰Ne scattering are compatible with available experimental data. The spin-rotation functions calculated for elastic p¹⁶O and p²⁰Ne scattering within the independent-nucleon model differ qualitatively from their counterparts calculated within the α-cluster model involving dispersion.     

A perturbative quantum chromodynamical calculation on productions of four jets in γe,ep and γp collisions

Various cross sections of jet and hadron productions through the hard parton-parton scattering in ψe,ep and ψp collisions are calculated by perturbative quantumchromodynamics. Attention is paid on the differences of results through the hard partonparton scattering due to the differences of the quark and gluon distribution functions between ψ andp ore.     

The imaginary part of the helicity nonflip C = −1 exchange amplitudes in elastic scattering between 6 and 14 GeV

Using accurate data on the differential cross sections for elastic scattering of particles and antiparticles on protons from 6 to 14 GeV, the projection of the C = ?1 exchange amplitude onto the dominant diffractive amplitude is measured. Strong peripherality in impact parameter space is observed for all the measured amplitudes with peak values scaling with the interaction radius. The zero of the imaginary part of the C = ?1 exchange amplitude in K^±p scattering moves to smaller t values as the energy increases from 6 to 14 GeV. The p^±p exchange amplitude is more peripheral than the π^±p and K^±p counterparts and an unexpected energy dependence is observed.     

NegativeP′-pole parameters and vanishing total cross sections in high energy πN scattering

In πN forward scattering the conventionalP′-pole can be simulated by two vacuum poles with α(0)<0 and different signs of the residues. In the regions ?0.3≦ α _p ′(0)≦?0.1 and ?0.8≦α _p ′'(0)≦?0.4 the practically identical fits to the πN scattering data from 8 to 65 GeV/c yield 0.98≦α _p (0)<1. The dispersion theoretical sum rule for the scattering lengtha ⁽⁺⁾ is fulfilled because of the negativeP′ residue; it is used as a finite-energy sum rule withN=8 GeV/c.     

Collision-induced light scattering spectra and pair-polarizability trace and anisotropy of gaseous neon

New empirical pair-polarizability trace and anisotropy parameters, consistent with the spectroscopic measurements of neon gas at room temperature are obtained by fitting the calculated lineshapes and their first few even moments to the measured polarized and depolarized light scattering spectra. Good agreement with ab initio results in the literature is obtained and profiles calculated with these models are in excellent agreement with experiments.     

Raman Scattering of amorphous selenium films

First order Raman scattering measurements are presented for thin film evaporated a-Se. High temperature films yield polarized and depolarized spectra that are very similar to those of bulk a-Se. Low temperature in situ studied films indicate increased disorder and a considerable reduction in the intensity of the ring attributed 112 cm^?1 peak. The Raman spectra of higher temperature films are consistent with a small number of rings and ordered chains that arise from constraints on the dihedral angle. Films deposited at low temperature suggest a reduction in chain order and ring population as might arise from a weakening of constraints on the dihedral angle.     

Analysis of <Emphasis Type="Italic">p</Emphasis><Superscript>10</Superscript>B scattering within Glauber theory

The differential cross sections for p ¹⁰B scattering are calculated at the energies of 197, 600, and 1000 MeV within Glauber theory. The contributions of single and double collisions are taken into account in the multiple-scattering operator. The contributions of proton collisions with nucleons belonging to various (1s, 1p) shells are estimated in the single-scattering cross sections. A comparison with experimental data and with the result of calculations in the distorted-wave Born approximation (DWBA) at 197 MeV showed that the differential cross sections for p ¹⁰B scattering are adequately described in the region forward scattering angles.     

Deep inelastic Compton scattering and large-p T pion photoproduction in QCD hard collision model

Inclusive photon(pion) production at large-p _T in γp collisions is studied in the framework of QCD perturbation theory, taking into account the effects due to parton transverse momenta. The contributions from various components of photons are equally important at relatively smallp _T (e.g.,p _T?4 Ge V/c at \(\sqrt s = 17GeV\) ). At largep _T, however, the contributions from the subprocesses with direct photon coupling are most important; quark Compton scattering is the dominant subprocess in inelastic Compton scattering.     

The stopping of slow75As recoil atoms in He,Ne and H2

Recent measurements of the 2p—1s X-ray line in theK ^? p atom indicate that the 1s level shift is very different from the theoretical prediction based on the extrapolation from theK ^? p scattering data. Deloff and Law have suggested that an anomalously large Coulomb effect could be responsible for this discrepancy. We examine this possibility by carrying out an explicit model calculation, using the method by which Sauer demonstrated the possible existence of an anomalously large Coulomb effect in the proton-proton system. Our conclusion is that if there exists an anomalous Coulomb effect which explains theK ^? p atomic level shift result, then the same effect would cause a serious conflict with theK ^? p scattering data above threshold.     

Electromagnetic contributions to proton- and neutron-4He scattering

A proper treatment of various electromagnetic contributions toN-⁴He scattering enables one to determinen(p)-⁴He observables fromp(n)-⁴He data. Several calculations ofn-⁴He observables considering different electromagnetic effects are presented. It is shown that the contribution of thep-⁴He Coulomb corrections ton-⁴He polarizations and differential cross sections dominates over other electromagnetic effects forθ _c.m.≧30°. For smaller scattering angles, neutron magnetic scattering is important and produces a divergingn-⁴He differential cross section atθ=0° and a large peak (Mott-Schwinger effect) in the polarization. The influence of thep- andn-⁴He vacuum polarizations on then-⁴He observables is found to be small.     

A new “parametrization” of the differential cross section for elastic scattering

A new parametrization of the differential cross section for elastic scattering is proposed. The parametrization incorporates correct analytic properties of the differential cross section and is based on optimized polynomial expansions of an analytic function. It is, in principle, valid for all energies and all angles. The parametrization has been tested for pp, $\text{p}\text{p}$, pd, π^± and K^±p elastic scattering at high energies and small angles. The results of the new fits are compared with those of the old ones. It has been found that with the same number of parameters one obtains practically the same values of χ². However, the new values of physical quantities, such as slope, α and (dσ/dt)₀, in most cases differ considerably from those obtained by the old parametrization. In particular, it has been found that the slope of the differential cross section for pp, $\text{p}\text{p}$, pd and K^±p elastic scattering increases continuously as the forward direction is approached.     

Arithmetic of strings

We incorporate the string theory into the number theoretic formulation based on arithmetic geometry. The string theory is generalized p-adically and interpreted on an arithmetic surface. A p-adic multi-loop scattering amplitude is constructed.     

Scattering Processes of Excited Muonic Atoms by Molecular Hydrogen

The coupled-channel approach of an excited exotic atom scattering from a hydrogen molecule in the rigid-rotator approximation is developed. The K-matrix method is used to solve the set of coupled collisional equations in the space-fixed (SF) framework for the systems pμ+H₂, dμ+D₂, pμ+D₂, and dμ+H₂. The elastic and Stark mixing cross-sections for scattering on molecular ortho- and para-states are calculated for the principle quantum number n = 2 and collisional energies E≥0.1 eV.     

Dispersion analysis of the K±p forward scattering amplitudes

The currently available experimental data on the K^±p forward scattering amplitudes are analyzed by three different methods: a discrepancy-function method, the Haber-Schaim linear extrapolation method, and a method based on a once-subtracted dispersion relation. Substantially more data are used than in previous analyses. The results of the three methods are found to be in good qualitative agreement. Predictions are obtained for the value of the effective KNY coupling constant and for the real parts of the K^±p forward scattering amplitudes over a wide range of energies.