Features about pion production in 2.1A and 3.7AGeV 4He–nucleus interactions up to and out of kinematical limit

The shower particle multiplicity characteristics are studied in 2.1A and 3.7A GeV 4He interactions with emulsion nuclei. The dependencies on emission direction, energy, target size, and centrality are examined. The data are compared with the simulation of the modified FRITIOF model. The forward emitted pion multiplicity distributions exhibit KNO scaling. The decay or peaking shaped curves characterize the pion multiplicity distributions. The decay shape is suggested to be due to a single source contribution and the peaking one results from a multisource superposition. The forward emitted pion is created from fireball or hadronic matter. The target nucleus is the origin of the backward one, regarding the nuclear limiting fragmentation hypothesis.

X-ray diffraction in perfect t × l crystals. Rocking curves

A general formalism, based on the Takagi–Taupin equations, for calculating rocking curves in perfect t\times l crystals is presented. It includes nonsymmetrical scattering, refraction, and ordinary and anomalous absorption. t and l may be varied independently. In the limit of a semi-infinite crystal, the standard results from the fundamental theory are retrieved. For crystal dimensions less than the extinction length, the theory converges to the kinematical limit. Simulations for germanium and silicon show significant influence of crystal finiteness. When dynamical effects are prominent, the curves exhibit various degrees of asymmetry and the full width at half-maximum is generally larger than the corresponding Darwin width. This is attributed to combined Laue and Bragg contributions which are shifted with respect to each other owing to refraction.

Determination of crystal imperfection by X-ray diffraction in a strong acoustic field

A study of X-ray diffraction in single silicon and quartz crystals in a strong ultrasonic field has been carried out. The dependence of diffraction intensity I(w) on sound amplitude w has been obtained right up to the kinematical limit Ik = I(∞). It is shown that the ratio η = I(∞)/I(0) depends on the crystal quality. Experimental data for different reflections, sound frequencies and X-ray wavelengths are compared with the model calculations for several lattice-distortion mechanisms.