Surprising result seen in primordial matter inside atom smasher

Physicists at the Relativistic Heavy Ion Collider, located on Long Island, have detected a potential primordial phase transition that occurred in the early universe. During the birth of the cosmos, space was incredibly hot and dense, preventing the formation of atoms. Instead, the newborn universe consisted of quarks and gluons, forming a smoothly flowing soup known as quark-gluon plasma.

As the universe expanded and cooled down, the soup transitioned into a gas of protons and neutrons, marking a phase change similar to water turning from vapor to liquid to ice. However, the exact energy and density thresholds of this ancient transition have remained elusive. In recent years, physicists have been smashing gold ions together at near-light speeds inside the RHIC accelerator to recreate the conditions of the big bang.

Researchers analyzing data from these collisions have noticed an unexpected signal from the STAR experiment, which appears to be a dip in fluctuations of the transverse momentum—the momentum perpendicular to the gold ions' direction. This observation, reported in Physical Review Letters, suggests a possible critical point where the phase transition occurs.

Understanding this critical point could provide insights into the evolution of the early universe and the behavior of matter at its highest densities, such as within neutron stars. However, further analysis of the STAR data is necessary to confirm whether this signal is indeed a phase transition or merely a reflection of changes in the types of particles being created at different energy levels.