Since then, several groups have studied antimatter-catalyzed micro fission/fusion engines in the lab (sometimes "antiproton" as opposed to "antimatter" or "antihydrogen").
This is inconsistent with predictions from most models of dark matter sources, in which the positron and antiproton excesses are correlated.
As a result, scientists had to develop a number of techniques for creating and handling intense beams of antiprotons.
Protons consist of two up quarks and one down quark, while antiprotons consist of two anti-ups and an anti-down.
The divergence indicates that at a low temperature hydrogen-antihydrogen will not be produced, rather proton/antiproton and electron/antielectron.
For example, the charges of the proton and antiproton must sum to exactly zero.
Several methods for the liquid-propellant thermal antimatter engine using the gamma rays produced by antiproton or positron annihilation have been proposed.
Whereas the common hydrogen atom is composed of an electron and proton, the antihydrogen atom is made up of a positron and antiproton.
