The collider accelerates the nuclei of heavy atoms to nearly the speed of light and smashes them together to produce elemental particles, antiparticles and exotic materials like quarks, muons and plasmas. 'Pretty much every event can contribute.'Īntimatter can be created in small amounts with a collider like RHIC and analyzed. 'All of the data we collected in 2011 is from 500 million events (collisions between two heavy gold ions),' Xin said.

Then came correlating their momentum from creation to destruction, typically a few nanoseconds. The first task was to determine which particles produced in a collision were indeed antiprotons and whether any two were in close enough proximity to influence each other. Xin, a student of Geurts, applied methods developed in his thesis to the analysis. But this is the first time we've been able to quantify it.' 'We've been studying the interaction between nucleons (particles that make up an atom's nucleus) for decades, and we've always thought the forces between antimatter particles are the same as for matter. thesis focuses on rather exotic systems called muonic atoms. 'This discovery isn't a surprise,' said Xin, whose Ph.D. Measuring distances that small involves both sophisticated equipment and sophisticated calculations. One femtometer is one-millionth of a nanometer a nanometer is one-billionth of a meter.įor antiprotons measured at RHIC, the scattering length was roughly 7.41 femtometers, and the effective range was 2.14 femtometers, nearly equivalent to their proton counterparts. The effective range indicates how close particles need to be for their charges to influence each other, like magnets.īoth are measured in femtometers. The scattering length is a measurement of how particles deviate as they travel from source to destination their paths are visible as three-dimensional traces captured by STAR (which is short for Solenoid Tracker at RHIC). Brookhaven's story on the discovery appears here. Department of Energy's Brookhaven National Laboratory. The find was reported in Nature on behalf of the more than 500 scientists, including Geurts, who work on the STAR experiment, part of the Relativistic Heavy Ion Collider (RHIC) at the U.S. It may not give us a solution to the bigger problem, but we most definitely removed one option,' he said. The interactions between two antimatter particles turn out to be quite similar to matter particles. 'It could have been that antimatter didn't have the same attractive force as matter and would have helped explain how these differences, during the initial part of the Big Bang, might have resulted in antimatter not having survived in the shape of stars and planets, as matter did,' Geurts said. Physicists are still trying to understand why they see so few antiparticles in nature even though particles and antiparticles were produced in equal amounts and annihilate each other on contact. Like all matter and antimatter, both were created at the instant of the Big Bang. 'This is about the subtle difference in the way matter and antimatter interact with each other,' said Rice physicist Frank Geurts.Īntiprotons carry the opposite electrical charge and spin that protons do.

This gave scientists a fundamental new way to understand the force that holds together the nuclei in antimatter and how this compares to matter. Specifically, the team measured two important parameters: the scattering length and the effective range of interaction between two antiprotons. Kefeng Xin, a graduate student at Rice, is one of a handful of primary authors who revealed evidence this week that the attractive force between antiprotons is similar to that between protons - and measured it. 4, 2015) - Due to the diligence of a Rice University student and his calculations, humanity now knows a little more about the universe. The discovery gives physicists new ways to look at the forces that bind matter and antimatter. Image: Scientists working at Brookhaven National Laboratory, including physicists at Rice University, have announced the first measurements of the attractive force between antiprotons.

Antimatter star