Dynamics of Antimatter-Atom Collisions

Angular and energy differential electron emission cross sections in collisions between antiprotons and helium atoms

“…Although numerous theoretical studies addressed the question of the anti-cusp[26][27][28] over the last decades, there is no experimental observation of the anti-cusp for anti-proton impact.Figures 2 and 3 show our DDCS for single ionization at 50 and 100 keV anti-proton impact energies within the framework of the CDW-EIS and the CTMC methods. Several prominent features are observed in the DDCS: slow electrons are mainly ejected in the backward direction; fast electrons are ejected along the broad ridge identified as the binary encounter (BE) ridge; and the void around the projectile is identified as the so-called anti-cusp.…”

Ionization of Hydrogen and Hydrogenic Ions by Antiprotons

“…That is, comparison of electron-and proton-impact collisions reflects a change in projectile charge sign and projectile mass simultaneously, whereas comparison of antiproton-and protonimpact isolates the differences arising from the varying charge sign. Considerable insight has been obtained in the last decade by comparing the ratio of double to single ionization [2], the spectrum of electrons ejected in ionization [3], and the variation of stopping power [4,5] (the well known Barkas effect), presented by antimatter-impact.…”

Interaction of antiproton with helium based on ab-initio calculations

“…At 10 keV the DDCS are generally smaller than for 50 or 100 keV. Despite the numerous theoretical studies investigations into the anti-cusp [31,42,43] over the last decades, there is still no experimental observation of the anti-cusp in anti-proton impacts. Slow electrons are possibly ejected into the backward direction and the fast electrons are ejected along the broad ridge identified as the binary encounter (BE) ridge.…”

“…The anti-cusp supposes that a well defined gap must exist in the energy spectrum of the ionized electron in the direction of the projectile. Numerous theoretical studies have addressed the question of anti-cusp from different authors [29][30][31][32][33][34]. To the best of our knowledge, only the total ionization cross section data is so-far available from experiments and there are no available ab initio calculations for differential ionization cross sections for antiproton helium impact.…”