In particle physics, antimatter is a material composed of antiparticles, which have the same mass as particles of ordinary matter, but opposite charges, lepton numbers, and baryon numbers. Collisions between particles and antiparticles lead to the annihilation of both, giving rise to variable proportions of intense photons (gamma rays), neutrinos, and less massive particleŠantiparticle pairs. The total consequence of annihilation is a release of energy available for work, proportional to the total matter and antimatter mass, in accord with the massŠenergy equivalence equation, E = mc2.

Antiparticles bind with each other to form antimatter, just as ordinary particles bind to form normal matter. For example, a positron (the antiparticle of the electron) and an antiproton (the antiparticle of the proton) can form an antihydrogen atom. Physical principles indicate that complex antimatter atomic nuclei are possible, as well as anti-atoms corresponding to the known chemical elements. Studies of cosmic rays have identified both positrons and antiprotons, presumably produced by collisions between particles of ordinary matter. Satellite-based searches of cosmic rays for antideuteron and antihelium particles have yielded nothing.

There is considerable speculation as to why the observable universe is composed almost entirely of ordinary matter, as opposed to an even mixture of matter and antimatter. This asymmetry of matter and antimatter in the visible universe is one of the great unsolved problems in physics. The process by which this inequality between particles and antiparticles developed is called baryogenesis.

Antimatter in the form of anti-atoms is one of the most difficult materials to produce. Antimatter in the form of individual anti-particles, however, is commonly produced by particle accelerators and in some types of radioactive decay. The nuclei of antihelium have been artificially produced with difficulty. These are the most complex anti-nuclei so far observed. Read more ...

In the News ...

Antimatter Is Both a Particle and a Wave, New Experiment Confirms   Live Science - May 8, 2019
Antimatter isn't just made of antiparticles, it's also made of waves. Now we know that this holds true even at the level of a single antimatter particle. Physicists have known for a long time that just about everything - light and other forms of energy, but also every atom in your body - exists as both particles and waves, a concept known as particle-wave duality. That's been shown again and again in experiments. But antimatter particles, which are identical to their matter partners, except for their opposite charge and spin, are much more difficult to experiment with. These twins of matter flit into existence fleetingly, usually in massive particle accelerators. But now, physicists have shown at the level of a single positron - an antimatter twin of the electron - that antimatter, too, is made of both particles and waves.

The Most Precise Measurement of Antimatter Yet Deepens the Mystery of Why We Exist   Live Science - April 5, 2018
Scientists have made the most precise measurement of antimatter yet, and the results only deepen the mystery of why life, the universe, and everything in it exists. The new measurements show that, to an incredibly high degree of precision, antimatter and matter behave identically. Yet those new measurements can't answer one of the biggest questions in physics: Why, if equal parts matter and antimatter were formed during the Big Bang, is our universe today made up of matter?