48th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 62, Number 8
Monday–Friday, June 5–9, 2017;
Sacramento, California
Session N5: Antimatter Collisions at Low Energies
10:30 AM–12:30 PM,
Thursday, June 8, 2017
Room: 310
Co-Sponsoring
Units:
DAMOP GEC
Chair: Thomas M. Miller, Boston College
Abstract ID: BAPS.2017.DAMOP.N5.2
Abstract: N5.00002 : Positronium collisions with atoms, protons, and antiprotons*
11:00 AM–11:30 AM
Preview Abstract
Abstract
Author:
Ilya Fabrikant
(University of Nebraska-Lincoln)
Recently observed similarities between positronium (Ps) scattering and electron scattering from
several atoms and
molecules [1] in the intermediate energy range were explained [2,3] by the dominance of the electron
exchange interaction with the target atom or molecule. An explicit proof of this equivalence was given
using the framework of the impulse approximation [2], valid above the Ps ionization threshold. For lower
collision energies a pseudodopotential method [3] was developed. It was successfully applied to the
calculation of Ps scattering from heavy rare gas atoms, and gave results in good agreement with those of
the beam experiments [1]. The same method was applied to Ps collisions with molecular hydrogen [4].
In general we observe the similarity between electron and Ps scattering at energies above the Ps ionization
threshold. However, below the threshold the two sets of cross sections are different because of the
different nature of the long-range interaction between the projectile and the target, the polarization
interaction in the case of electron collisions and the van der Waals interaction in the case of Ps
collisions. In particular the Ramsauer-Townsend minimum is not seen in theoretical cross sections for the
heavy rare gas atoms. The second part of this talk will summarize recent results on the threshold behavior
of Ps collisions with protons and antiprotons [5]. Partial cross sections for elastic and quasielastic
scattering exhibit oscillations as functions of $\ln E$ where $E$ is the Ps energy.
The quantum-mechanical threshold behavior of
hydrogen and antihydrogen formation show features which make them different from results of
classical trajectory Monte Carlo simulations.
$^1$ S. J. Brawley, S. Armitage, J. Beale, D. E. Leslie, A. I. Williams, and G. Laricchia, Science
{\bf 330}, 789 (2010).
$^2$ I. I. Fabrikant and G. F. Gribakin, Phys. Rev. Lett. {\bf 112}, 243201 (2014).
$^3$ I. I. Fabrikant and G. F. Gribakin, Phys. Rev. A {\bf 90}, 052717 (2014).
$^4$ R. S. Wilde and I. I. Fabrikant, Phys. Rev. A {\bf 92}, 032708 (2015).
$^5$ I. I. Fabrikant, A. W. Bray, A. S. Kadyrov, and I. Bray,
Phys. Rev. A {\bf 94}, 012701 (2016).
*In collaboration with G. F. Gribakin, R. S. Wilde, and I. Bray. Supported by the US National Science Foundation.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2017.DAMOP.N5.2