Scientists working on the STAR detector at Brookhaven National Laboratory in the United States reported that they could obtain convincing evidence of two physical phenomena predicted more than 80 years ago — the formation of the matter directly from light and that magnetism can bend polarized photons in a vacuum. The results of the study are published in the journal Physical Review Letters.
The STAR detector is one of four experiments at the Relativistic Heavy Ion Collider (RHIC) at the Brookhaven National Laboratory of the US Department of Energy.
The main discovery is that pairs of electrons and positrons — particles of matter and antimatter – can be created directly by the collision of very energetic photons, which are quantum “packets” of light.
This transformation of energetic light into the matter is a direct consequence of Einstein’s famous equation E = mc2, which states that energy and matter, or mass, are interchangeable. Nuclear reactions in the Sun and in nuclear power plants regularly convert matter into energy. Now scientists have converted light energy back into the matter directly in one step.
The second result shows that the path of light passing through a magnetic field in a vacuum bends differently, depending on how this light is polarized. This polarization-dependent deviation, known as double refraction, occurs when light passes through certain materials.
Both results were obtained due to the ability of the RHIC STAR detector to measure the angular distribution of particles formed during sliding collisions of gold ions moving almost at the speed of light. Such possibilities did not exist when, in 1934, physicists Gregory Breit and John Wheeler first described the hypothetical possibility of a collision of light particles with the formation of pairs of electrons and their antimatter analogs, known as positrons.
“In their article, Breit and Wheeler noted that it is almost impossible to do this,” one of the authors of the study, physicist Zhangbu Xu, a member of the RHIC STAR collaboration, is quoted in a press release from the Brookhaven Laboratory. – There were no lasers then. But Breit and Wheeler proposed an alternative-the acceleration of heavy ions. And that’s exactly what we do at RHIC.”
Scientists accelerated gold ions to 99.995 percent of the speed of light in the two rings of the collider.
“We have two clouds of photons moving in opposite directions with sufficient energy and intensity so that when two ions slide past each other without colliding, these photon fields can interact,” explains Xu.
STAR physicists tracked the interactions and looked for predicted electron-positron pairs. But such pairs of particles can also be created using short-term states of “virtual” photons. To distinguish real photons from virtual ones, the authors analyzed the regularities of the angular distribution of each electron in relation to its partner positron. These distribution patterns differ for pairs formed by the interaction of real and virtual photons.
“We also measured the energy, mass distribution, and quantum numbers of the systems. They are consistent with theoretical calculations and confirm that this could happen with real photons,” says another participant in the study, Daniel Brandenburg, a researcher at the Brookhaven Laboratory. — Our results provide clear evidence of direct one-step creation of matter-antimatter pairs as a result of light collisions, as originally predicted by Breit and Wheeler.”
In another experiment, scientists proved that polarization affects the interaction of light with a magnetic field in a vacuum. This effect, similar to how a wavelength-dependent deviation divides white light into a rainbow, was predicted back in 1936. But in the experiment, the phenomenon of polarization-dependent deflection of light in a vacuum was observed for the first time.