Chi Yang, a physicist at Shandong University and a member of the STAR Collaboration. “The cloud of photons surrounding the gold ions in one of RHIC’s beams is shooting into the strong circular magnetic field produced by the accelerated ions in the other gold beam,” said Dr. STAR’s ability to measure the tiny deflections of electrons and positrons produced almost back-to-back in these events also gave the physicists a way to study how light particles interact with the powerful magnetic fields generated by the accelerated ions. Daniel Brandenburg, a physicist at DOE’s Brookhaven National Laboratory and a member of the STAR Collaboration. “Our results provide clear evidence of direct, one-step creation of matter-antimatter pairs from collisions of light as originally predicted by Breit and Wheeler,” said Dr. The STAR team observed a total of 6,085 exclusive electron-positron pairs in Au+Au collisions at RHIC. “We have two clouds of photons moving in opposite directions with enough energy and intensity that when the two ions graze past each other without colliding, those photon fields can interact,” Dr. “So, when the ions are moving close to the speed of light, there are a bunch of photons surrounding the gold nucleus, traveling with it like a cloud.”Īt RHIC, the scientists accelerate gold (Au) ions to 99.995% of the speed of light in two accelerator rings. “And that arrangement of perpendicular electric and magnetic fields of equal strength is exactly what a photon is a quantized particle of light.” “If the speed is high enough, the strength of the circular magnetic field can be equal to the strength of the perpendicular electric field,” Dr. Accelerating such a charged heavy ion to very high speeds generates a powerful magnetic field that spirals around the speeding particle as it travels - like current flowing through a wire. And their alternative is exactly what we are doing at RHIC.”Ī gold ion, with 79 protons, carries a powerful positive charge. “Lasers didn’t even exist yet! But Breit and Wheeler proposed an alternative: accelerating heavy ions. Zhangbu Xu, a physicist at DOE’s Brookhaven National Laboratory and a member of the STAR Collaboration. “In their paper, Breit and Wheeler already realized this is almost impossible to do,” said Dr. In their original study, the researchers realized the near impossibility of achieving gamma-ray collisions in existing Earth-based experiments and proposed an alternative approach with photon collisions originating from highly charged nuclei passing each other at ultra-relativistic speeds. Wheeler studied the theory of the reverse process of ‘collision of two light quanta’ to create electron-positron pairs. In 1934, physicists Gregory Breit and John A. When an electron at rest annihilates with its antimatter counterpart, a positron, the process results in the emission of two photons. Image credit: Brookhaven National Laboratory. As the ions pass one another without colliding, two photons (γ) from the electromagnetic cloud surrounding the ions can interact with each other to create a matter-antimatter pair: an electron (e-) and positron (e+). Two gold ions (red) move in opposite direction at 99.995% of the speed of light (v, for velocity, = approximately c, the speed of light).
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |