Backscattered flux generated by protons with energy above 1 TeV in a lead absorber

Detailed simulations of cascade processes are used to analyze the properties of the backscattered particle flux from a lead absorber (in comparison with an iron absorber). The energy dependence of the albedo flux and the spatial and angular distributions of its various components are considered.     

Alignment phenomenon in superfamilies with energy above 400 TeV

Summary The analysis is presented of the alignment phenomenon of the most energetic particles in gamma-hadron families with energy above 400 TeV. It is shown that the effect increases with energy. At an energy of about 1000 TeV the fraction of aligned families is equal to 0.26±0.09 for carbon chambers and 0.43±0.17 for lead chambers. From the comparison with simulated families it is seen that it exceeds the background value at about 2.0 standard deviations. A possible interpretation of the phenomenon is discussed. Paper presented at the Special Session on very high-energy cosmic-ray interactions (superfamilies) of the XXIV International Cosmic-Ray Conference, Rome, August 28–September 8, 1995.     

Determination of the inelasticity partial coefficients of pions and protons in iron in the energy range 0.5–5.0 TeV

The inelasticity coefficients for pion and proton interactions with iron nuclei at energies 0.5–5.0 TeV are measured for the first time. The experimental results are compared with conclusions of the multiple scattering theory.     

Polarization of light backscattered by small particles

We study scattering of light by wavelength-scale spherical, cubic, and spheroidal particles as well as clusters of spherical particles for equal-volume-sphere size parameters 4≤x≤10 and refractive indices 1.1≤m≤2.0. Such particles exhibit three specific features in the regime of backscattering: first, the intensity shows a backscattering peak; second, the degree of linear polarization for unpolarized incident light is negative; and, third, the depolarization ratio is double-lobed. We find that the overall characteristics of the scattering-matrix elements can be explained by an internal field composed of waves propagating in opposite directions near the particle perimeter and forming standing waves, as well as a wave propagating forward with the wavelength of the internal medium. When moving from the central axis of the particle toward its perimeter, the internal field changes from a forward-propagating wave with a wavelength dictated by the particle refractive index toward a standing wave with an apparent wavelength of the surrounding medium. The mapping of the internal field to the scattered far field is like an interference dial where rotation of the dial by a quarter of a wavelength on the particle perimeter results in a change from a destructive to constructive interference feature in the angular patterns (or vice versa). The dial is a manifestation of a well-known rule of thumb: the number of maxima or minima in the scattering-matrix elements is given by the size parameter. We explain the backscattering peak as deriving from the backward-propagating internal wave near the particle perimeter. Negative polarization follows from the spatial asymmetry of the internal fields: inside the particle, the fields are amplified near the central plane perpendicular to the polarization state of incident light, resulting in more pronounced interference effects for the perpendicular polarization than for the parallel polarization. The double-lobe feature in the depolarization results from the same internal-field structure with leading cross-polarized fields located slightly different from the copolarized fields. We discuss practical implications of these findings for the retrieval of particle sizes, shapes, and refractive indices from observations and laboratory experiments.     

Determination of energies of cosmic-ray nuclei in the region above 1 TeV

A method is proposed for measuring energies of particles in the region above 1 TeV. The method is based on detecting the greatest specific energy deposition in hadronic cascades propagating in dense matter. This makes it possible to improve accuracy in measuring energy by thin calorimeters in studying the energy spectra of high-energy cosmic rays at high altitudes. Attainable accuracies in measuring energy are considered for protons and He nuclei. The results of a relevant simulation are compared with the results of a satellite-borne experiment with Kosmos-1713.     

Angular and energy distribution of electrons produced by 200–500 keV protons in gases

The cross beam method was used to measure double differential ionization cross sections for electron production by 200–500 keV protons incident on a molecular beam. The ejected secondary electrons were detected by an electron multiplier and an electrostatic 90 °-spectrometer which was movable in the scattering chamber from 18 °–155 ° with respect to the incident proton direction. After the elimination of disturbing electric and magnetic fields, electrons were measured at energies down to 1 eV. The absorption of the very slow electrons along their path through the spectrometer could be minimized by using a relatively low gas pressure in the scattering chamber of a few 10^?5 Torr. The efficiency of the electron detector was determined with an electron source whose emission rate per solid angle was known. Absolute cross sections and their angular dependence were obtained by measuring the slow electrons—ejected with a relatively high rate—without the molecular beam; these data being used to normalize the electron spectra acquired with the molecular beam. Ionization cross sections with 300 keV protons incident on helium are discussed and except for the very slow electrons, a good agreement is found with results of Ruddet al.     

Iron oxide and iron carbide particles produced by the polyol method

Iron oxide (γ-Fe₂O₃) and iron carbide (Fe₃C) particles were produced by the polyol method. Ferrocene, which was employed as an iron source, was decomposed in a mixture of 1,2-hexadecandiol, oleylamine, and 1-octadecene. Particles were characterized using Mössbauer spectroscopy, X-ray diffraction, and transmission electron microscopy. It was found that oleylamine acted as a capping reagent, leading to uniform-sized (12-16 nm) particles consisting of γ-Fe ₂O₃. On the other hand, 1-octadecene acted as a non-coordinating solvent and a carbon source, which led to particles consisting of Fe₃C and α-Fe with various sizes.     

The spectrum of protons produced in pp collisions at 31 GeV total energy

Data are reported on the distributions in longitudinal and transverse momentum of protons produced in the range 0.5 < x < 1.0 (x = Feynman variable) and 0.2 < p_T² < 1.8 (GeV/c)² in proton-proton collisions at 31 GeV c.m. energy at the CERN ISR. The invariant inelastic cross section shows a peak at high longitudinal momenta. The shape of this peak suggests substantial production of states with masses up to at least 7 GeV.     

Bremsstrahlung produced by colliding particles in an external electric field

We have used the nonrelativistic dipole Born approximation to study bremsstrahlung from two colliding charged particles in a uniform electric field. We have calculated the differential cross sections for photon emission as the system transitions into various states of internal motion. We find the cross sections exhibit spatial anisotropy due to the uniform electric field, and that oscillations can arise that are probably due to interference effects between the colliding particles.Khabarovskii State Pedagogical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 46–50, July, 1994.     

Ionization energy losses of fast charged particles produced in matter

Ionization energy losses of an ultrarelativistic electron produced in matter are considered. The interference of the proper Coulomb field of the product particle and the electromagnetic wave that this particle emits is shown to be significant at impact-parameter values that make a dominant contribution to the ionization energy losses. The effect is shown to exert virtually no influence on the ionization energy losses of the particle.     

On the probability of repeated interactions of leading particles in the interior of a nucleus at energies above 10 TeV

An analysis of experimental information that comes from cosmic-ray studies and from accelerator experiments leads to the conclusion that the production of new particles is not an instantaneous event, but that it spans a spacetime interval exceeding substantially nucleon-nucleon distances. This means that the production process extended in space and time cannot be reduced to a simple superposition of nucleon-nucleon collisions.     

Exotic hyperfullerenes produced by irradiation of 20 MeV protons

Transmission electron microscopy (TEM) images demonstrate that two graphitic nanoparticles, a nanoparticle and a nanotube, as well as two nanotube pairs can join together under specific angles in bump-like, neck-like and L patterns with saddle surfaces at the junction. A negatively curved surface containing eight-member rings has first been observed in the L type structure. It is suggested that the large energy transfer of the proton-carbon collision plays an important role in forming such structures.     

Correlations associated with small angle protons produced in proton-proton collisions at 31 GeV total energy

High energy inelastic protons with $\text{x = 2 p}{}_{\mathrm{<mtext>L</mtext>}}\text{/s}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{> 0.99}$ observed in 15.3/15.3 GeV proton-proton collisions at the CERN ISR are accompanied by particles whose angular distribution is confined to a narrow cone in the opposite direction. In constrast, lower energy protons (0.72 < x < 0.84) are accompanied in addition, by particles emitted at larger angles. The ratio of the associated charged multiplicities is approximately 0.4.     

Scattering of polarized protons by iron and nickel isotopes

Elastic and inelastic scattering of polarized protons (E = 17.2, 20.4, 24.6 MeV) by ^{54, 56}Fe and ^{58, 60, 62} Ni have been investigated. Most data can be readily accommodated by standard optical-model and DWBA procedures, including full Thomas coupling. The 2⁺₁ state (1.41 MeV) in ⁵⁴Fe is peculiar because the inelastic scattering data require deformation parameters for the central and spin-orbit parts of the nuclear potential that differ by a factor 2 to 3; moreover, this anomaly shows a marked energy dependence.     

Quantitative analysis of depolarization of backscattered light by stochastically inhomogeneous dielectric particles

We determine the relationship between the depolarization properties of inhomogeneous particles and the statistical parameters of their internal refractive-index distributions. Our analysis demonstrates that the linear depolarization ratio of backscattered light by an inhomogeneous particle is approximately proportional to both the squared standard deviation and the squared correlation length of the particle's internal refractive-index distribution. We verify this result by conducting rigorous numerical studies using the finite-difference time-domain method. This improved understanding of light depolarization by inhomogeneous structures may enhance polarization-based biomedical optical imaging techniques.