This image is an artist's conception that illustrates the history of the cosmos, from the Big Bang and the recombination epoch that created the microwave background, through the formation of galactic superclusters and galaxies themselves. The dramatic flaring at right emphasizes that the universe's expansion currently is speeding up.
Scientists working with ALICE (A Large Ion Collider Experiment), a heavy-ion detector on the Large Hadron Collider (LHC) ring, have made precise measurements of particle mass and electric charge that confirm the existence of a fundamental symmetry in nature. The investigators include Brazilian researchers affiliated with the University of São Paulo (USP) and the University of Campinas (UNICAMP).
"After the Big Bang, for every particle of matter an antiparticle was created. In particle physics, a very important question is whether all the laws of physics display a specific kind of symmetry known as CPT, and these measurements suggest that there is indeed a fundamental symmetry between nuclei and antinuclei," said Marcelo Gameiro Munhoz, a professor at USP's Physics Institute (IF) and a member of the Brazilian team working on ALICE.
The findings, reported in a paper published online in Nature Physics on August 17, led the researchers to confirm a fundamental symmetry between the nuclei of the particles and their antiparticles in terms of charge, parity and time (CPT).
These measurements of particles produced in high-energy collisions of heavy ions in the LHC were made possible by the ALICE experiment's high-precision tracking and identification capabilities, as part of an investigation designed to detect subtle differences between the ways in which protons and neutrons join in nuclei while their antiparticles form antinuclei.
Munhoz is the principal investigator for the research project "High-energy nuclear physics at RHIC and LHC", supported by São Paulo Research Foundation (FAPESP). The project - a collaboration between the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory in the United States and ALICE at the LHC, operated by the European Organization for Nuclear Research (CERN) in Switzerland - consists of experimental activities relating to the study of relativistic heavy-ion collisions.
