Target Structure Induced Suppression of the Ionization Cross Section for Very Low Energy Antiproton-Hydrogen Collisions

Abstract

Low energy antiprotons have been used previously to give benchmark data for theories of atomic collisions. Here we present measurements of the cross section for single, nondissociative ionization of molecular hydrogen for impact of antiprotons with kinetic energies in the range 2-11 keV, i.e., in the velocity interval of 0.3-0.65 a.u. We find a cross section which is proportional to the projectile velocity, which is quite unlike the behavior of corresponding atomic cross sections, and which has never previously been observed experimentally.

Development of a monoenergetic ultraslow antiproton beam source for high-precision investigation

“…The MUSASHI was designed to work in two operation modes for p extraction. Long bunched p beams for atomic collision experiments [5][6][7] were obtained by the DC extraction mode. Pulsed beams from the MUSASHI were obtained by the pulse extraction mode, which was used for H experiments [3].…”

“…The studies of these exotic atoms can test CPT invariance and the weak equivalence principle [4]. The collision dynamics by such low energy p can reveal such exotic antiprotonic atom formation [5] and the ionization processes of atoms and molecules [6,7]. The study of the nuclear surface via pA þ formation and annihilation is also considered [8,9].…”

Manipulation of the magnetron orbit of a positron cloud in a Penning trap

“…It is usually necessary to counteract the heating caused by the field, and this is commonly achieved by the introduction of a cooling gas into the system. RW compression reduces particle loss via diffusion to the electrode walls of the trap 8 and has found widespread use, for instance in tailoring antiparticle plasmas and clouds for antihydrogen [15][16][17][18][19][20][21] and antiproton 22,23 physics, and in manypositron experimentation. 24,25 A possible application is in the development of multicell traps for the storage of large numbers of positrons, 26,27 where it is envisaged that an array of microtraps will be filled from a positron accumulator (see e.g., Refs.…”

Wave packet simulations of antiproton scattering on molecular hydrogen

“…Mixed matter-antimatter many-body systems provide a field of study, which exceeds the pure annihilation effects and allows for comparison with the dynamics of ordinary molecular systems. Examples of such many body systems includes, e.g., antihydrogen-hydrogen 7 , antiprotonic helium 8,9 and various antiproton -gas collisions investigated by the ASACUSA collaboration in the antiproton collisional kinetic energy regime of 2-11 keV 10 . In this work we have investigated the collision an antiproton (p) with molecular hydrogen as a model system for more complex antiparticle -molecular interactions.…”

“…The H 2 -p system is interesting from a practical point of view as residual H 2 gas exists in most high energy colliders, and antiprotons are created in various experiments, resulting in scattering of antiprotons on H 2 molecules 9 . Previous work on this system focused on the high-energy 11 and the low-energy collision region investigating antiproton and proton cross sections for ionization a) Electronic mail: hans.karlsson@kemi.uu.se b) Electronic mail: mkowalew@uci.edu; Now at: Chemistry Department, University of California, Irvine, California 92697-2025, United States and excitation of hydrogen molecules as well as energy spectra of the ionized electrons 10,[12][13][14] . In previous work the influence of collisions in the energy regime above 100 eV was investigated which mainly leads to ionized reaction products 15 .…”