My universe is different from the one you think you know

Science 5 November 2010:
Vol. 330. no. 6005, p. 789
DOI: 10.1126/science.1192322
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Brevia
Electron-Like Scattering of Positronium
S. J. Brawley, S. Armitage,* J. Beale, D. E. Leslie, A. I. Williams, G. Laricchia

Positronium (Ps), a hydrogen-like atom composed of an electron and its antimatter partner, the positron, is formed in considerable quantities whenever positrons interact with matter. It has unexpectedly been found to scatter from a wide variety of atoms and molecules in a way very similar to that of a bare electron moving at the same velocity, despite Ps being neutral and twice the mass.

UCL Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK.
* Present address: Chemical Engineering, Imperial College London, London SW7 2AZ, UK.

Present address: Atomic Weapons Establishment, Aldermaston, Reading RG 7 4PR, UK.

Present address: Brunel University, Uxbridge UB8 3PH, UK.


To whom correspondence should be addressed. E-mail: g.laricchia@ucl.ac.uk