Searcharxiv⌕ Search

arXiv subjects

G. Bonomi

Publications and source records attributed to G. Bonomi.

44 records · Page 3Linked to original sources
arXiv2003

Positron plasma diagnostics and temperature control for antihydrogen production

Production of antihydrogen atoms by mixing antiprotons with a cold, confined, positron plasma depends critically on parameters such as the plasma density and temperature. We discuss non-destructive measurements, based on a novel, real-time analysis of excited, low-order plasma modes, that provide comprehensive characterization of the positron plasma in the ATHENA antihydrogen apparatus. The plasma length, radius, density, and total particle number are obtained. Measurement and control of plasma temperature variations, and the application to antihydrogen production experiments are discussed.

physics.plasm-ph↗
arXiv2000

On the different role of protons and neutrons in antinucleon annihilations on nuclei

We compare data of antineutron and antiproton annihilation cross sections on different targets at very low energies. After subtracting Coulomb effects, we observe that the ratio between the antineutron proton and antiproton proton annihilation cross sections is an oscillating function of the energy at momenta smaller 300 MeV/c. This nontrivial behavior is confirmed by the analysis of the relative number of antiproton-neutron and antiproton-proton annihilations in nuclei. We show that a part of the strong shadowing phenomena in antiproton-nucleus annihilations can be explained in terms of this oscillation, while a part requires different explainations.

nucl-th↗
arXiv2000

Limits on the low energy antinucleon-nucleus annihilations from the Heisenberg principle

We show that the quantum uncertainty principle puts some limits on the effectiveness of the antinucleon-nucleus annihilation at very low energies. This is caused by the fact that the realization a very effective short-distance reaction process implies information on the relative distance of the reacting particles. Some quantitative predictions are possible on this ground, including the approximate A-independence of antinucleon-nucleus annihilation rates.

nucl-th↗
arXiv2000

A phenomenological analysis of antiproton interactions at low energies

We present an optical potential analysis of the antiproton-proton interactions at low energies. Our optical potential is purely phenomenological, and has been parametrized on data recently obtained by the Obelix Collaboration at momenta below 180 MeV/c. It reasonably fits annihilation and elastic data below 600 MeV/c, and allows us for an evaluation of the elastic cross section and rho-parameter down to zero kinetic energy. Moreover we show that the mechanism that depresses antiproton-nucleus annihilation cross sections at low energies is present in antiproton-proton interactions too.

nucl-th↗
arXiv1999

Coulomb corrections to low energy antiproton annihilation cross sections on protons and nuclei

We calculate, in a systematic way, the enhancement effect on antiproton-proton and antiproton-nucleus annihilation cross sections at low energy due to the initial state electrostatic interaction between the projectile and the target nucleus. This calculation is aimed at future comparisons between antineutron and antiproton annihilation rates on different targets, for the extraction of pure isospin channels.

nucl-th↗
arXiv1999

Antiproton annihilation on light nuclei at very low energies

The recent experimental data obtained by the OBELIX group on $\bar{p}$D and $\bar{p}^4$He total annihilation cross sections are analyzed. The combined analysis of these data with existing antiprotonic atom data allows, for the first time, the imaginary parts of the S-wave scattering lengths for the two nuclei to be extracted. The obtained values are: $Im a^{sc}_0 = [- 0.62 \pm 0.02 ({stat}) \pm 0.04 ({sys})] fm$ for $\bar{p}$D and $Im a^{sc}_0 = [- 0.36\pm 0.03({stat})^{+0.19}_{-0.11}({sys})] fm$ for $\bar{p}^4$He. This analysis indicates an unexpected behaviour of the imaginary part of the $\bar{p}$-nucleus S-wave scattering length as a function of the atomic weight A: $|Im a^{sc}_0|$ ($\bar{p}$p) > $|Im a^{sc}_0|$ ($\bar{p}$D) > $|Im a^{sc}_0|$ ($\bar{p}^4$He).

nucl-th↗
arXiv1999

Annihilation of antiprotons on nuclear targets at low energies: a simple analysis

We set up a plane wave impulse approximation (PWIA) formalism for the analysis of the annihilation cross sections of antinucleons on nuclear targets at very low momenta (below 100 MeV/c), where semiclassical approximations can't be applied. Since, as we test here, PWIA fails in reproducing the unexpected ``inversion'' behavior of the $\bar{p}p$ and $\bar{p}-$nucleus annihilation cross sections found in a recent experiment\cite{obe1,obe2} we discuss some further possibilities, with a special attention to the optical potential model.

nucl-th↗