Target Mass Number Research Articles

Temperatures of the fragment spectra in high-energy proton-nucleus collisions

The temperatures of the evaporation nucleons in high-energy protonnuclous collisions have been calculated in terms of the laboratory energy of the projectile and the mass number of the target. The calculated temperature ratios for different processes compare favourably with the previously fitted values.

Cluster Excitation in Hadron-Nucleus Collisions at Medium and High Energies

A phenomenological cluster excitation model is proposed to describe the cumulative particle emission in nuclear reactions initiated by energetic projectiles. Clusters consisting of few nucleons are assumed to act as subunits of the nucleus in quasi-free inelastic collisions with the projectile. They absorb considerable energy and momentum in this process and decay statistically into the kinematically allowed exit channels. The dynamical properties of nuclear clusters are assumed to be the same for all target nuclei investigated. Good agreement of model calculations with experimental data is reached for a wide region of the target mass number and for incidence energies from 0.6 GeV to 400 GeV.

(γ,p) Reaction on Light Nuclei in theΔ(1232)Resonance Region

Momentum spectra of protons from the ($\ensuremath{\gamma}$, $p$) reaction have been measured at ${\ensuremath{\theta}}_{p}=30\ifmmode^\circ\else\textdegree\fi{}$ for $^{1}\mathrm{H}$, $^{2}\mathrm{H}$, $^{4}\mathrm{He}$, $^{9}\mathrm{Be}$, $^{12}\mathrm{C}$, and $^{16}\mathrm{O}$ with a tagged photon beam with energies from 187 to 427 MeV. By analysis of these inclusive proton spectra, cross sections for the pion photoproduction from the quasifree nucleon in the target nucleus and those for the photodisintegration of the quasifree two-nucleon system have been obtained as a function of the photon energy and of the target mass number.

Four-nucleon pickup reaction on 12 ⩽ A ⩽ 94 nuclei

The differential cross sections for the (d, 6Li) reaction on targets of 12C, 16O, 24Mg, 40Ca, 58Ni and 94Mo have been measured at E d = 54.2 MeV. The measured angular distributions have been analyzed by finite-range DWBA calculations, and spectroscopic factors for an α-cluster transfer have been extracted. In the DWBA analysis using an optical model with a phenomenological Woods-Saxon potential, the spin-orbit part of the deuteron optical potential played a significant role in reproducing the measured angular distributions but the spin-orbit part of the 6Li optical potential had a minor effect. Relative spectroscopic factors extracted from the present data were compared with theoretical predictions together with the results from the (p, pα) reaction. The relative spectroscopic factors for 1p-shell nuclei were in quantitative agreement with theoretical predictions. However, there were certain discrepancies between the spectroscopic factors extracted from the (d, 6Li) reaction and those from the (p, pα) reaction, and the discrepancies increased with target mass number.

Study of particle emission following π − absorption at rest

Spectra of particles (n, p, d, t, 3He) following absorption of π − at rest were analyzed in terms of a model taking direct as well as cascade emission into account. Spectra of complex particles give evidence for absorption on heavier nucleon correlations than deuterons. The mass number of these nucleon groups tends to increase with increasing target mass number.

Scaling the central region in 50 GeV/c π− interactions with emulsion nuclei

In the present work we investigate the onset of scaling in 50 GeV/c π− interactions with emulsion nuclei. The dependence of scaling on the target mass number is also discussed.

Transmission coefficients for light projectiles

Transmission coefficients forn, p,2H,3H,3He and4He generated from global optical potentials available in the literature are parametrized in terms of simple empirical expressions which are smooth functions of the target mass number and projectile energy. These empirical forms predict the transmission coefficients and the magnitude of the scattering matrix satisfactorily for nuclei over the whole periodic table and energies up to 50 MeV. They are a convenient input in statistical model calculations where transmission coefficients are required.

Elastic scattering of 65 MeV polarized protons

Elastic scattering of 65 MeV polarized protons from 25 nuclei ($^{16}\mathrm{O}$---$^{209}\mathrm{Bi}$) has been measured. The volume integral of the real central part of the optical potential (${J}_{R}$) shows a behavior similar to the binding energy curve for the target mass number. The mean square radius of the real central part of the optical potential is found to obey the relation ${〈{r}^{2}〉}_{\mathrm{pot}}=(0.937\ifmmode\pm\else\textpm\fi{}0.012){A}^{\frac{2}{3}}+(6.42\ifmmode\pm\else\textpm\fi{}0.21)$ ${\mathrm{fm}}^{2}$. By comparing with the systematics of the charge distributions obtained from electron scattering data, it is found that the effective two-body interaction range between an incident proton and a nucleon in the target has a target mass number dependence given by ${〈{r}^{2}〉}_{\mathrm{int}}=(0.132\ifmmode\pm\else\textpm\fi{}0.013){A}^{\frac{2}{3}}+(4.24\ifmmode\pm\else\textpm\fi{}0.24)$ ${\mathrm{fm}}^{2}$. Assuming this relation, root mean square radii of the point nucleon distributions are obtained. The dependences of the ${J}_{R}$ value and the ${〈{r}^{2}〉}_{\mathrm{pot}}$ value on the mass number and energy obtained here are compared critically with recent microscopic optical potential calculations.NUCLEAR REACTIONS $^{16}\mathrm{O}$, $^{24}\mathrm{Mg}$, $^{28}\mathrm{Si}$, $^{40}\mathrm{Ar}$, $^{40,44,48}\mathrm{Ca}$, $^{46,48,50}\mathrm{Ti}$, $^{54,56}\mathrm{Fe}$, $^{58,60,62,64}\mathrm{Ni}$, $^{89}\mathrm{Y}$, $^{90}\mathrm{Zr}$, $^{98,100}\mathrm{Mo}$, $^{144}\mathrm{Sm}$, $^{208}\mathrm{Pb}$, $^{209}\mathrm{Bi}(\stackrel{\ensuremath{\rightarrow}}{\mathrm{p}}, p)$, $E=65$ MeV; measured $\ensuremath{\sigma}(\ensuremath{\theta})$, $A(\ensuremath{\theta})$; deduced optical-model parameters, mean-square nuclear radii, and volume integrals for the real central potential.

Particle Ratios in Hadron-Nucleus Collisions and a Collective Interaction

Particle ratios K lireh and J5IJrch in proton-nucleus collisions at high energies are calculated within the framework of two classes of models, one of which (collective models) assumes that a collective interaction is responsible for multi-hadron production in the central region and another (non-collective models) does not assume such. The collective models predict that the particle ratios increase as the target mass number increases while the non-collective models predict that they decrease provided that both KIJreh and plJ[ch are dominated by the central component.

A study of pion production in 4.5 GeV/ c)/nucleon 4He interactions with nuclear targets

Inelastic interactions of 4He nuclei at the incident momentum of 4.5 GeV/ c)/nucleon with pure Li, C, Al, Cu and Pb targets were studied in the SKM-200 streamer chamber. Cross sections and their dependence on the target mass number for fragmentation processes were obtained. The multiplicities, transverse momenta and rapidities of negative pions as well as their correlations were analyzed separately for “central” and “peripheral” collisions. A comparison of the results with the predictions of some theoretical models is presented.

Broad structure intspectra from (He3,t) reactions atEHe3=130MeV: Its angle and target-mass dependence

Triton spectra from /sup 3/He-induced reactions on /sup 27/Al, /sup 59/Co, /sup 93/Nb, and /sup 197/Au targets at E3He = 130 MeV have been measured in the 7.5/sup 0/< or =theta/sub L/< or =24/sup 0/ angular range in 1.5/sup 0/ steps. The spectra exhibit a broad structure; the centroid energy E/sub c/ and the full width at half maximum GAMMA of this ''bump'' are found to be independent of the target mass number A. Their average values are E-bar/sub c/ = 87 MeV and Gamma-bar = 48 MeV with estimated errors of about +- 2 MeV in both cases. Within the error bars the bump cross section is found to be consistent with A/sup 1/2/ proportionality and tends to decrease exponentially with angle; however, A/sup 1/3/ dependence cannot be excluded. In addition, the angular distributions possibly show indications for a weak oscillation pattern.

Optical reaction cross-sections for light projectiles

The optical reaction cross-sections forn, p,2H,3He,3He and4He for several global optical potentials available in the literature have been parametrized in terms of simple empirical expressions which are smooth functions of the target mass number and the projectile energy. The empirical forms are 5–10% accurate over the periodic table and energy-range upto 50 MeV. They can be conveniently used in calculations where the optical reaction cross-sections are required as input. The calculation of proton spectra in the (n, p) reaction at 14 MeV is discussed.

Effects of imaginary potentials on the vector analyzing power in elastic scattering of polarized deuterons

In elastic scattering from nuclei, the vector analyzing powers of polarized deuterons are found to be strongly affected by the imaginary parts of optical potentials. A definite relationship is postulated between the analyzing power and the imaginary potential depth. The relationship shows that the shell-closure effect of the analyzing power observed for Se isotope targets is the reflection of the isotope dependence of the imaginary potential. Coupled-channel calculations show that some low-lying levels of the target nuclei are responsible for the isotope dependence. By the use of the relationship, deuteron scattering from medium-weight nuclei at incident energies of about 15 MeV are reanalyzed to give a systematic variation with target mass number for the potential parameters, which is emphasized by a nearly constant volume integral of the real potential per pair of interacting nucleons.

Systematics in the volume integrals of the imaginary part of nucleon, deuteron, and mass-3 optical potentials

Volume integrals of the imaginary part of d, t, and /sup 3/He optical potentials are obtained from existing phenomenological analyses over the range of target mass numbers A=50--208. Comparison of these values with those for nucleons shows that the volume integrals for nulceon, deuteron, and mass-3 projectiles, averaged over this A range, are in the ratio of 1:2:3. The present results are thus in good agreement with predictions of the simple folding model.

Rapidity distribution in hadron–nucleus interactions in emulsion at 22.8, 50, 400, and

Rapidity distributions in hadron–nucleus interactions in nuclear emulsion for energies 22.8, 50, 400, and [Formula: see text] are presented. The dependence of rapidity distributions on incident energy and the target mass number (A) has been investigated. The results favour multiperipheral models based on Glauber–Gribov multiple scattering theory.

Systematic features of the pion-nucleus interaction

We analyze pion elastic-scattering data for $^{40}\mathrm{Ca}$ and $^{48}\mathrm{Ca}$ using a covariant theory of the optical potential developed previously. Combining these results with the information obtained from the analysis of pion scattering from $^{12}\mathrm{C}$ and $^{16}\mathrm{O}$ reported earlier, we are able to discuss the systematics of the pion-nucleus optical potential. Our model contains a first-order optical potential which is obtained from a parameter-free calculation. The parameters of a second-order potential are determined by requiring that the sum of the first-and second-order potentials provides a fit to the elastic-scattering data. The parameters of the second-order potential exhibit a smooth dependence on energy and target mass number. These parameters have a marked resonance behavior. We find that the maximum value of the magnitude of the imaginary part of the second-order potential occurs at about 150 MeV while the first-order potential has a maximum for the magnitude of the imaginary part at about 240 MeV. The imaginary part of the first-order potential has a width at half maximum of about 200 MeV. This corresponds to a kinematic broadening of the (3,3) resonance due to the effects of the Fermi motion of the target nucleons. (This increased width is unrelated to the effects of the true absorption process or of collision broadening.) We also find a significant isospin violation in the second-order potential. For example, the imaginary part of the second-order potential for ${\ensuremath{\pi}}^{\ensuremath{-}}$ scattering is found to be systematically larger than that for ${\ensuremath{\pi}}^{+}$ scattering for nuclei with $N=Z$. An explanation for this feature of the optical potential is presented.NUCLEAR REACTIONS Elastic scattering of pions from $^{40}\mathrm{Ca}$ (40-241 MeV) and $^{48}\mathrm{Ca}$ (130 MeV). Systematics of first- and second-order optical potentials.

Angular distributions of preequilibrium reactions within a generalized exciton model

The phase space used in the exciton model of preequilibrium reactions has been extended by including the total linear momentum of the exciton gas. The densities of exciton states with conserved total energy and momentum are estimated with the partition-function method in the saddle-point approximation. Introducing these quantities into the closed-form equations of the exciton model the angular distributions of nucleon induced preequilibrium reactions are calculated for various incident energies and target mass numbers. A normalizing factor is used to fit the absolute value of the differential cross section. The results are compared with experiment as well as with calculations following previous approaches to the description of preequilibrium angular distributions. The experimental data are reproduced to the same extent as within other attempts to calculate preequilibrium angular distributions.

Activation yield curves of photonuclear reactions for multielement photon activation analysis

The activation yield curves have been presented for a number of photonuclear reactions in the energy range from 30 to 68 MeV, in order to evaluate quantitatively the interferences due to competing reactions in multielement photon activation analysis. The general features of the yields as functions of both target mass number and excitation energy were elucidated from the data obtained, discussion being given on the results in terms of the reaction mechanism. Simultaneous neutron activation due to appreciable neutron production from the converter and surrounding materials has also been studied, and, finally, the magnitudes of interferences in real multielement analysis were given in the form of their energy dependences.

Nucleus-nucleus total cross sections for light nuclei at 1.55 and 2.89 GeV/cper nucleon

We have measured total cross sections for protons, dueterons, $\ensuremath{\alpha}$ particles, and $^{12}\mathrm{C}$ on hydrogen, deuterium, helium, and carbon targets at 1.55 and 2.89 GeV/c nucleon using the geometry transmission method. In addition, we measured the inelastic cross sections and elastic slope parameters for reactions initiated by deuterons, $\ensuremath{\alpha}$ particles, and $^{12}\mathrm{C}$. Our results are in good agreement with Glauber theory predictions, but the factorization relation ${\ensuremath{\sigma}}_{T}(\mathrm{AA})=\frac{{[{\ensuremath{\sigma}}_{T}(\mathrm{AB})]}^{2}}{{\ensuremath{\sigma}}_{T}(\mathrm{BB})}$ is not a good guide. We find ${\ensuremath{\sigma}}_{T}\ensuremath{\simeq}144{({{A}_{T}}^{\frac{1}{3}}\ensuremath{-}{{A}_{p}}^{\frac{1}{3}}\ensuremath{-}1.48)}^{2}$ mb and ${\ensuremath{\sigma}}_{\mathrm{IN}}\ensuremath{\simeq}78{({{A}_{T}}^{\frac{1}{3}}+{{A}_{p}}^{\frac{1}{3}}\ensuremath{-}1.25)}^{2}$ mb, where ${A}_{T}({A}_{p})$ is the atomic mass number of the target (projectile).NUCLEAR REACTIONS $^{12}\mathrm{C}(^{12}\mathrm{C}, X)$, ($\ensuremath{\alpha}, X$), ($d, X$), ($p, X$), $E=0.87 \mathrm{and} 2.10$ GeV/nucleon; measured total cross section, total inelastic cross section, and slope parameter of elastic scattering.

Global Viewpoint on Nuclear-Particle-Emission Cross Sections at Intermediate Energies

It follows from the independent-particle picture of the nucleus that the cross section for the reaction (d, /sup 6/Li) depends upon the target mass number A as approx. A/sup -3/./sup 33/, this result indicates the significance of a recent empirical observation. The energy-integrated cross sections for emission of p, d, /sup 3/H, /sup 3/He, and /sup 4/He from Mg, Ni, and Ag nuclei bombarded by a 235-MeV pion beam show some features suggestive of nuclear structure. (AIP)