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Heaviest particles of antimatter seen in a lab survive for about 10 billionths of a second before crashing into collider’s detector They were gone as soon as they appeared, but for a fleeting moment they were the heaviest particles of antimatter a laboratory has seen. Scientists in the US produced a clutch of antihelium particles, the antimatter equivalents of the helium nucleus, after smashing gold ions together nearly 1bn times at close to the speed of light. The discovery of antihelium at the Relativistic Heavy Ion Collider at Brookhaven national laboratory in New York will aid the search for exotic phenomena in the distant universe, including antimatter versions of stars and even galaxies. Antimatter looks and behaves like normal matter but has one crucial difference: particles of antimatter have an equal and opposite charge to those that make up the world around us. When antimatter meets matter, the two annihilate one another, leaving nothing but a burst of energy. Researchers at the US laboratory recorded 18 antihelium particles that survived for about 10 billionths of a second before they crashed into the collider’s detector and vanished in the tiniest of fireballs. “Antihelium is stable, so if it doesn’t encounter anything it will survive forever,” said Aihong Tang, a physicist at the laboratory. “Unless there is a major breakthrough in accelerator technology, this will be the heaviest antimatter made for decades to come.” Antihelium is the heaviest breed of antimatter created by scientists, with each particle is roughly 10 million billion times lighter than a grain of sand. The next heaviest that is stable is antilithium, but this is so rare the Brookhaven collider would have to run for thousands of years to detect just one particle. Antimatter is central to one of the greatest mysteries of our existence. Equal amounts of matter and antimatter were created in the Big Bang and should have destroyed each other in one enormous cosmic explosion. But for reasons unknown, only normal matter seems to have survived to make up all we know in the visible universe. Particles of antimatter were first discovered in 1932 when a US researcher found antielectrons, or positrons, among the debris of cosmic ray collisions. Cosmic rays are highly charged streams of particles that can span vast stretches of space. Paul Dirac, the British physicist who predicted antimatter, speculated that some regions of the universe might be home to entire galaxies made of antimatter. The latest research, published in the journal Nature , is a benchmark for space-based experiments that will hunt for antimatter elsewhere in the universe. Next week, the penultimate mission of the space shuttle will deliver a $2bn instrument called the alpha magnetic spectrometer (AMS) to the International Space Station. From there, it will scour space for signs of heavenly bodies made from antimatter. “Collisions among cosmic rays near Earth can produce antimatter, but the odds of these collisions producing an intact antihelium nucleus are so vanishingly small that finding even one would strongly suggest that it had drifted to Earth from a distant region of the universe dominated by antimatter,” said Hans Georg Ritter at the University of California, Berkeley. “Antimatter doesn’t look any different from ordinary matter, but AMS finding just one antihelium nucleus would suggest that some of the galaxies we see are antimatter galaxies.” Particle physics Physics Ian Sample guardian.co.uk