For the first time, physicists used lasers to freeze antimatter.
In a new experiment, an ultraviolet laser suffered from the thermal concerns of the antihydrogen atoms and cooled the antiatoms to above absolute zero. This technique for slowing down antimatter – the charged counterpart as opposed to normal matter – could help scientists build the first antimatter molecules. Taming unruly antimatter with laser light can also allow physicists to measure the properties of antiatoms much more accurately, researchers report in the April 1 issue of the journal Nature. Comparing antiatoms with normal atoms could prove some fundamental symmetries of the universe.
Lasers can cool atoms by dampening the motion of atoms with a flood of light particles or photons (SN: 3/8/21). But it was hard to cool the antimatter because, on the one hand, “it’s really hard to make antimatter,” says Takamasa Momose, a spectroscopist at the University of British Columbia in Vancouver.
To craft antihydrogen atoms, Momose and colleagues mixed antiprotons with positrons, the electron antiparticles, at CERN's particle physics lab near Geneva. For several hours, a laser beam tuned to a specific frequency of UV light caused the anti-hydrogen atoms to slow down by up to 90 meters per second to about 10 meters per second.
Future observations of supercooled antihydrogen could test an idea called load parity time symmetry or CPT (SN: 19/02/20). This principle of physics says that normal atoms should absorb and emit photons with the same energies as their antimatter similarities. Even the slightest differences between hydrogen and antihydrogen can undermine modern theories of physics, says study co-author Makoto Fujiwara, a particle physicist at the Canadian National Particle Acceleration Center, TRIUMF, also in Vancouver.
Similarly, Einstein's theory of gravity predicts that matter and antimatter should fall to Earth at the same rate. Laboratory experiments that dropped laser-cooled antiatoms – rather than hot and nervous ones – could provide a clearer view of the effects of gravity.
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