Spectra ofp,d, andtfrom relativistic nuclear collisions

Abstract

Inclusive energy spectra of protons, deuterons, and tritons were measured with a telescope of silicon and germanium detectors with a detection range for proton energies up to 200 MeV. Fifteen sets of data were taken using projectiles ranging from protons to 'oAr on targets from "Al to '"U at bombarding energies from 240 MeV/nucleon to 2.1 GeV/nucleon. Particular attention was paid to the absolute normalization of the cross sections. For three previously reported reactions, He fragment cross sections have been corrected and are presented. To facilitate a comparison with theory the sum of nucleonic charges emitted as protons plus composite particles was estimated and is presented as a function of fragment energy per nucleon in the interval from 15 to 200 MeV/nucleon. For low-energy fragments at forward angles the protons account for only 25% of the nucleonic charges. The equal mass Ar plus Ca systems were examined in the center of mass. Here at 0.4 GeV/nucleon Ar plus Ca the proton spectra appear to be nearly isotropic in the center of mass over the region measured. Comparisons of some data with firestreak, cascade, and fluid dynamics models indicate a failure of the first and a fair agreement with the latter two. In addition, associated fast charged particle multiplicities (where the particles had energies larger than 25 MeV/nucleon) and azimuthal correlations were measured with an 80 counter array of plastic scintillators. It was found that the associated multiplicities were a smooth function of the total kinetic energy of the projectile.

The possibility of time resonance (explosion) phenomena in high-energy nuclear reactions

“…Since the slope of energy spectra noticeably increases with increasing angle, the increasing contribution of compound-nucleus states with larger values of t n and τ n is connected with the formation of heavier compound nucleons with less velocity (in the laboratory system). This agrees with the observations of more distinct oscillations for intermediate emission angles [1,3,6].…”

“…Experimental indications for the existence of time resonances are in the steeper energy decrease in the spectra for larger emission angles θ and of the more distinct oscillations in spectra for the intermediate emission angles θ in the laboratory system (between the minimal and maximal experimental values), which are observed in [1][2][3][4][5][6]. Nevertheless, for small angles, the last oscillation peak in spectra (for the largest energies E) can be connected with the pure kinematical effect of direct or peripherical processes in the laboratory system.…”

“…3 and 4 contain some calculated inclusive energy spectra σ inc,k (E k ), in arbitrary units and in semi-logarithmic scale, in comparison with the experimental data from [4,6,9] (see also [8]). …”

“…For lighter projectiles (from p to 20 Ne) with energies above 1 -10 Gev/nucl, studies have observed structureless, exponentially decaying inclusive and non-inclusive energy spectra, often accompanied by slight oscillations over the range of projectiles and projectile energies, targets, and registered final fragments (see, for example, [1][2][3][4][5][6][7][8]). For heavier projectiles these phenomena were observed even for smaller energies (see, for instance, [9]).…”

A History of Central Collisions at the Bevalac

“…This was placed in a thin spherical scattering chamber designed by Hans Gutbrod, on the outside of which were 80 scintillation counters covering the whole forward hemisphere (see Figs. 11 & 12), because we had learned that in order to select high multiplicity events you have to de tect almost all the charged particles. An exhaustive set of data was published for protons 8 and pions 9 ' J0 with beams as heavy as ^Ar, but it was soon discovered that the many different theoretical models then availeNe all agreed with the proton data within a factor of two. Clearly, single particle inclusive measurements with associated multiplicity were not sufficient to distinguish between the models.…”