Function Of Target Mass Research Articles

Proton-induced fission at 190 MeV ofnatW,197Au,natPb,208Pb,and232Th

Proton-induced fission at 190 MeV of ${}^{\mathrm{nat}}\mathrm{W},$ ${}^{197}\mathrm{Au},$ ${}^{\mathrm{nat}}\mathrm{Pb},$ ${}^{208}\mathrm{Pb},$ and ${}^{232}\mathrm{Th}$ is studied by means of an innovative method based on activation analysis. The fission-product mass distribution is reconstructed from the fission-product yields, which are obtained from off-line observed $\ensuremath{\gamma}$-ray spectra. For ${}^{\mathrm{nat}}\mathrm{W}{,}^{197}\mathrm{Au}{,}^{208}\mathrm{Pb},$ and ${}^{\mathrm{nat}}\mathrm{Pb}$ the fission process results in a symmetric mass distribution. In the case of ${}^{232}\mathrm{Th}$ the mass yield curve is decomposed into a mixed symmetric-asymmetric contribution originating from fissioning nuclides in the neighborhood of the target mass and a purely symmetric contribution from very neutron-deficient nuclides. The fission cross sections are extracted by integrating over the reconstructed mass distribution. The width of the mass distribution is determined as a function of target mass. The results for the fission cross sections are compared with other experimental data as well as with theoretical model calculations using the LAHET and the ALICE-91 codes.

Some general properties of projectile fragments in 40Ar interactions in nuclear emulsions at 1.8 A GeV

An analysis of projectile fragments has been performed using 40Ar-emulsion interactions at 1.8 A GeV. The interaction mean free path of 40Ar nuclei was obtained on the basis of 4600 events which enabled one to calculate the total inelastic cross section. Correlations between the multiplicity of different charged particles were studied extensively to get an insight into the reaction mechanism. The average number of interacting nucleons of the projectile was calculated and compared with results from other experiments. Events with projectile fragments were divided into various reaction channels and several parameters like average emission angle and target particle multiplicities were studied as a function of target mass in different reaction channels. The projectile fragmentation properties were found to be independent of the target for peripheral collisions.

Target dependence of central rapidity Lambda production in sulfur-nucleus collisions at 200 GeV/c per nucleon.

Central rapidity {Lambda} production has been measured in sulfur collisions with Cu, Ag, and Pb at 200 GeV/{ital c} per nucleon. Lambdas produced in these collisions were identified by their charged decays recorded by a time projection chamber. The {Lambda} yields are compared as a function of target mass. For each target, the yields are reported as a function of {Lambda} transverse kinetic energy and zero degree energy (a measure of collision centrality). In each system, the data exceed predictions of the VENUS {ital size}{minus}2(4.02) model of sulfur-nucleus collisions. The observed excesses show no obvious variation with collision centrality from moderate to highly central collisions.

Global variables and forward baryons in 14.6 GeV/nucleon silicon-nucleus collisions

Experiment E814 measures transverse energy over nearly the full solid angle and charged particle multiplicity in the forward hemisphere in the center of mass frame. Experimental data on transverse energy and charged particle multiplicity indicate a large amount of stopping and rescattering. Protons and neutrons are measured and identified in a spectrometer covering a narrow cone around the beam axis. The multiplixity of beam rapidity nucleons is studied as a function of target mass and centrality of the collision. The results can be understood in terms of collision geometry and nuclear transparency. Conclusions on the in-medium cross section for already excited nucleons can be drawn from these data. We find a value consistent with the free nucleon-nucleon inelastic cross section.

Charged-pion production in noninclusive proton-nucleus interactions at 0.8 and 1.6 GeV incident energies.

Charged pions and light nuclei ({ital p}, {ital d}, {ital t}, {sup 3}He, and {sup 4}He) have been measured in the interaction of proton beams with C, Nb, and Pb targets at 0.8 and 1.6 GeV incident energies, using a large solid angle detector. From slices on the multiplicity of protonlike particles (free protons and protons bound in light fragments), the events have been sorted out into two classes corresponding to more peripheral and more central collisions. For each class of events, the mean value and the dispersion of the {pi}{sup +} and {pi}{sup {minus}} multiplicity distributions have been studied as a function of target mass and incident energy. Comparisons to the Liege intranuclear cascade predictions exhibit some discrepancies which are discussed.