Particle collider experiment recreates the Big Bang's primordial soup — and finds an unexpected twist

Key Points:

• Physicists at Brookhaven National Laboratory's RHIC smashed gold nuclei at near-light speeds and observed an unexpected dip in the variations of particles' transverse momentum, suggesting a possible "critical point" where nuclear matter changes phase.
• This critical point, if confirmed, would mark a transition in how nuclear matter transforms between quark-gluon plasma and ordinary matter, analogous to the critical point in water between liquid and steam.
• The STAR experiment detected the dip with a statistical significance of 5 sigma, making it very unlikely to be a random fluctuation, though researchers caution it is a hint rather than definitive proof of the critical point.
• The findings help map the equation of state for nuclear matter under extreme conditions, shedding light on how the early universe cooled from a quark-gluon plasma into protons and neutrons, and may also inform understanding of neutron star cores.
• Further work will involve comparing the data with theoretical models and additional measurements to confirm the critical point's existence and extract properties like the specific heat of the hot matter created in collisions.