Analyzing powers for πp elastic scattering at bombarding energies below the Δ(1232) resonance were measured at TRIUMF using the CHAOS spectrometer and a polarized spin target. This work presents π− data at six incident energies of 57, 67, 87, 98, 117, and 139 MeV, and a single π+ data set at 139 MeV. The higher energy measurements cover an angular range of 72°<~θc.m.<~180° while the lower energies were limited to 101°<~θc.m.<~180°. There is a high degree of consistency between this work and the predictions of the VPI/GWU group’s SM95 partial wave analysis.
Analysing power measurements for a 139 GeV PI+ beam (standard track).
Analysing power measurements for a 139 GeV PI- beam (standard track).
Analysing power measurements for a 117 GeV PI- beam (standard track).
Emission of intermediate mass fragments (IMFs) (Z>~3) from central collisions of 40Ar+45Sc (E/A=35–115 MeV), 58Ni+58Ni (E/A=35–105 MeV), and 86Kr+93Nb (E/A=35–95 MeV) was studied. For each system, the average number of IMFs per event increased with beam energy, reached a maximum, and then decreased. The beam energy of peak IMF production increased linearly with the combined mass of the system. The number of IMFs emitted at the peak also increased with the system mass. Percolation calculations showed a weaker dependence of the peak beam energy and the number of IMFs on the total mass of the system.
Uncertainty in EKIN is 1 PCT.
The angular distributions of the cross section, the proton analyzing power, and all proton polarization transfer coefficients of p→d elastic scattering were measured at 250 MeV. The range of center-of-mass angles was 10°–165° for the cross section and the analyzing power, and about 10°–95° for the polarization transfer coefficients. These are the first measurements of a complete set of proton polarization observables for p→d elastic scattering at intermediate energies. The present data are compared with theoretical predictions based on exact solutions of the three-nucleon Faddeev equations and modern realistic nucleon-nucleon potentials combined with three-nucleon forces (3NF), namely, the Tucson-Melbourne (TM) 2π-exchange model, a modification thereof (TM′) closer to chiral symmetry, and the Urbana IX model. Large effects of the three-nucleon forces are predicted. The inclusion of the three-nucleon forces gives a good description of the cross section at angles below the minimum. However, appreciable discrepancies between the data and predictions remain at backward angles. For the spin observables the predictions of the TM 3NF model deviate strongly from the other two 3NF models, which are close together, except for Kyy′. In the case of the analyzing power all 3NF models fail to describe the data at the upper half of the angular range. In the restricted measured angular range the polarization transfer coefficients are fairly well described by the TM′ and Urbana IX 3NF models, whereas the TM 3NF model mostly fails. The transfer coefficient Kyy′ is best described by the Urbana IX but the theoretical description is still insufficient to reproduce the experimental data. These results call for a better understanding of the spin structure of the three-nucleon force and very likely for a full relativistic treatment of the three-nucleon continuum.
Cross section and analyzing power measurements.
Proton polarization transfer coefficients.
Reaction mechanisms and multifragmentation processes have been studied for 64Zn+58Ni collisions at intermediate energies with the help of antisymmetrized molecular dynamics (AMD-V) model calculations. Experimental energy spectra, angular distributions, charge distributions, and isotope distributions, classified by their associated charged particle multiplicities, are compared with the results of the AMD-V calculations. In general the experimental results are reasonably well reproduced by the calculations. The multifragmentation observed experimentally at all incident energies is also reproduced by the AMD-V calculations. A detailed study of AMD-V events reveals that, in nucleon transport, the reaction shows some transparency, whereas in energy transport the reaction is much less transparent at all incident energies studied here. The transparency in the nucleon transport indicates that, even for central collisions, about 75% of the projectile nucleons appear in the forward direction. In energy transport about 80% of the initial kinetic energy of the projectile in the center- of-mass frame is dissipated. The detailed study of AMD-V events also elucidates the dynamics of the multifragmentation process. The study suggests that, at 35A MeV, the semitransparency and thermal expansion are the dominant mechanisms for the multifragmentation process, whereas at 49A MeV and higher incident energies a nuclear compression occurs at an early stage of the reaction and plays an important role in the multifragmentation process in addition to that of the thermal expansion and the semitransparency.
No description provided.
Average summed transverse momentum.
Kinematically complete events have been studied for the reactions dp→dpπ0 and dp→dnπ+ at projectile energies between 437 and 559 MeV. The measurement covers a range of pion momenta η=pπ,c.m.max/mπc from near the production threshold (η=0.32) to η=0.86 close to the NN→NNπ threshold. The measurements were performed at the CELSIUS storage ring with the PROMICE/WASA setup. Angular and spectral distributions of the charged ejectiles as well as total cross sections are decomposed into the fractions that can be attributed to a quasifree NN→dπ process with a spectator nucleon, and to a process involving all three nucleons. The quasifree contribution increases with energy and dominates from the NN→NNπ threshold on. The results are compared to calculations with a spectator model with and without dp final state interactions.
Two first points on energy correspond to different luminosities.
The elastic scattering of 600-MeV protons from light nuclei has been studied at the National Aeronautics Space Administration Space Radiation Effects Laboratory (SREL) synchrocyclotron. Differential cross sections have been obtained for the scattering of protons from hydrogen, deuterium, helium-3, and helium-4. Polarization was measured for deuterium and He4 nuclei. The p−p cross-section data are in excellent agreement with the predictions from the Livermore phase shifts. Small-angle p−D, p−He3 elastic scattering data are compared with calculations based on the multiple-scattering theories of Watson and Glauber.
No description provided.
No description provided.
No description provided.
The differential cross section for η production in reaction π−p→ηn has been measured over the full angular range at seven incident π− beam momenta from threshold to pπ−=747 MeV/c using the Crystal Ball multiphoton spectrometer. The angular distributions are S wave dominated. At 10 MeV/c above threshold, a small D-wave contribution appears that interferes with the main S wave. The total η production cross section σtot is obtained by integration of dσ/dΩ. Starting at threshold, σtot rises rapidly, as expected for S-wave-dominated production. The features of the π−p→ηn cross section are strikingly similar to those of the SU(3) flavor-related process K−p→ηΛ. Comparison of the π−p→ηn reaction is made with η photoproduction.
Total cross sections.
Differential cross section for the 4 lowest beam momenta.
Differential cross section for the 3 highest beam momenta.
Angular distributions of the α-particle production differential cross section from the breakup of 6Li and 7Li projectiles incident on a 208Pb target have been measured at seven projectile energies between 29 and 52 MeV. The α-breakup cross section of 6Li was found to be systematically greater than that of 7Li across the entire energy range. These data have been compared with previously reported results and with the predictions of continuum-discretized coupled channels (CDCC) calculations including resonant and nonresonant projectile breakup. The present data compare well with previous measurements, while the CDCC calculations provide a reasonable prediction of the relative α-breakup cross sections but underpredict their absolute values. The calculations confirm that a major factor in the enhancement of the 6Li to 7Li α-breakup cross section is the difference between the α-breakup thresholds of the two isotopes. These results have implications for structural studies of light exotic nuclei based on elastic scattering.
No description provided.
No description provided.
Charged particle multiplicities from high multiplicity central interactions of 158 GeV/nucleon Pb ions with Pb target nuclei have been measured in the central and far forward projectile spectator regions using emulsion chambers. Multiplicities are significantly lower than predicted by Monte Carlo simulations. We examine the shape of the pseudorapidity distribution and its dependence on centrality in detail.
Q(NAME=B) parameter is the total sum of the individual charges of the projectile fragments.
The PS185 experiment at LEAR/CERN has investigated strangeness production in antiproton-proton collisions with final states such as $\overline{\Lambda} \Lambda$, $\overline{\Sigma}^0 \Lambda + c.c$, $\overline{\Sigma^+} \Sigma^+$, $\overline{\Sigma^-} \Sigma^-$ and $K_S K_S$. Results are presented from a study of about 32,000 {$K_S K_S X$} events obtained at several antiproton momenta in the regions of 1.45 and 1.7 GeV/c. The $\overline{p} p \to K_S K_S \eta$ cross sections extracted at these momenta constitute the first measurement of this reaction in flight and are broadly consistent with expectations of a phase-space extrapolation of branching ratios from annihilation at rest.
No description provided.
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