AsianScientist (Nov. 19, 2015) – Human understanding of the early universe has taken another step forward after scientists successfully measured the forces that make antimatter particles stick together. The observations, published in Nature, were made using the Relativistic Heavy Ion Collider (RHIC)—a particle accelerator used to simulate and study conditions of the early Universe.
The RHIC lives at the US The Department of Energy’s Brookhaven National Laboratory (BNL) and the project is part of the STAR collaboration, composed of 52 institutions from 12 countries. This was the first time that scientists have been able to measure the forces between antimatter particles, in this case, antiprotons.
The STAR Collaboration’s findings may yield clues to one of the big mysteries of the cosmos—why is antimatter extremely rare in the cosmos we see today, when the Big Bang produced matter and antimatter in equal amounts.
To help uncover this mystery, the RHIC simulates the conditions just after the Big Bang, thus producing antimatter particles—antiprotons—enabling scientists to measure them for the first time.
To create these conditions, the RHIC first causes head-on collisions between gold ions moving at near light-speed, thus producing plasma of the smallest components of matter: the quarks and gluons that make up ordinary protons and neutrons. Quark-Gluon Plasma (QGP) is the hottest matter ever created in a laboratory—250,000 times hotter than the center of the Sun—at about four trillion degrees Celsius.
When QGP cools down, it produces abundant anti-nucleons, making it possible to observe interaction between the simplest system of anti-nucleons: antiprotons.
Learning how two antiprotons interact provides a foundation for understanding the structure and properties of more sophisticated anti-nuclei. The STAR collaboration measured the correlation of antiproton-antiproton pairs and compared this with the correlation of their anti-particle counterparts: proton-protons, with the help of the quantum theory of multi-particle correlation.
The researchers found that the force between antiprotons is attractive and strong, just like the force that holds ordinary protons together within the nuclei of atoms.
This sameness in the behavior of the forces suggests that matter and antimatter appear to comply with the current test of matter-antimatter symmetry, formally known as CPT—a fundamental symmetry of physical laws under the simultaneous transformations of charge conjugation (C), parity transformation (P) and time reversal (T). That points scientists towards more study of antimatter production, interaction and evolution mechanism to explain the matter-antimatter asymmetry. So the antimatter study has bright prospects.
The STAR-China group led by Professor Ma Yugang is one of main components of the whole STAR collaboration. The group includes Shanghai Institute of Applied Physics-CAS, University of Science and Technology of China, Tsinghua University, Central China Normal University, Institute of Modern Physics-CAS, and Shandong University and others.
The article can be found at: The STAR Collaboration (2015) Measurement of Interaction Between Antiprotons.
———
Source: Chinese Academy of Sciences.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.
