Search Results (6 total)

The Tevatron in Collider Run II (2001–present) is operating with 6 times more bunches, many times higher beam intensities and luminosities than in Run I (1992–1995). Electromagnetic long-range and head-on interactions of high intensity proton and antiproton beams have been significant sources of beam loss and lifetime limitations. We present observations of the beam-beam phenomena in the Tevatron and results of relevant beam studies. We analyze the data and various methods employed in operations, predict the performance for planned luminosity upgrades, and discuss ways to improve it.

Angular distributions have been measured for π^± elastic scattering at 50 MeV from ¹⁴C. Comparison with previously measured distributions for ¹²C shows a significant isotopic difference for π^- scattering. The data were analyzed using the second order Michigan State University optical potential proposed for low energy pion nucleus elastic scattering. Agreement with the data was obtained using the same density distributions for the protons and neutrons.

The decay of sup149Er was investigated by γ-ray spectroscopy. Based on these measurements the ssub1/2, dsub3/2, and hsub11/2 neutron states in sup149Er and the ssub1/2, dsub3/2, dsub5/2, and gsub7/2 proton states in sup149Ho were identified. A systematic examination of these proton states in N=82 isotones indicates a modest closure at Z=64, rather than a major one as suggested previously. Spherical Hartree-Fock-Bogolyubov calculations for even-Z N=81 and odd-Z N=82 nuclei are compared with experiment.

Differential cross sections for the reaction π⁺+d→p+p were measured for pion laboratory energies of 65, 72.5, 80, 95, 110, 125, and 140 MeV. The integrated cross sections for these energies were found to be 7.51±0.19, 7.91±0.16, 8.64±0.15, 9.61±0.15, 11.3±0.2, 11.7±0.3, and 11.3±0.3 mb, respectively. These values indicate that the centroid and width of the energy dependence for the resonance in this reaction is lower and greater, respectively, than predicted by most theoretical models of the process. Comparisons made with predictions by Blankleider and Afnan show a qualitative difference between experimental measurements and calculations of the P₄(cosθ) term in the polynomial expansion of the differential cross section. This may indicate a more important role for ρ-like exchange in the reaction mechanism than that included by the calculations.

NUCLEAR REACTIONS d(π⁺, p)p, E=65, 72.5, 80, 95, 110, 125, 140 MeV; measured absolute dσ / dΩ, deduced total cross section; obtained fits to P_n(cosθ) expansion; compared with Faddeev-type calculations for the reaction.

The two-prong annihilation channels for the p̅ p interaction at four center-of-mass energies between 2150 and 2240 MeV are described. The angular distributions in the dipion annihilations are in detail different from those obtained in a previous experiment. Resonance contributions in final states involving one or more neutrals are estimated. No evidence of formation of the T(2195) meson is observed.