Physicists reveal when nature’s strongest strength is weakened

We get closer to understanding when the strong nuclear power loosens its grip on the most basic components of fabric, lets quarks and gluons inside particles suddenly become a hot particle soup.

There is a special combination of temperature and pressure, where all three stages of water – liquid, ice and steam – are found at the same time. For decades, scientists have been looking for a similar “critical point” for substance controlled by the strong nuclear power that binds quarks and gluons to protons and neutrons.

Smashing ions in Particle Collides can create a condition in which the strong force breaks down and allows quarks and gluons to form a compliant “quark-gluon plasma”. But it is still unclear whether this transition is prior to a critical point. Xin Dong in Lawrence Berkeley National Laboratory in California and his colleagues have now come closer to cleaning it up.

They analyzed the number and distribution of particles created in the wake of a smash of two very energetic gold ions by the relativistic heavy ion collider at Brookhaven National Laboratory in New York State. Dong says they effectively tried to create a phase diagram for quarks and gluons – a map showing what types of substance the strong force allows to form in different circumstances. The new experiment did not determine the critical point on this map with great certainty, but it narrowed the area where it could be.

There is part of the phase diagram where the case “melts” to plasma gradually, as butter soft -paving on the counter, but the critical point would adapt to a more sudden transition, just as piles of ice suddenly appear in liquid water, says Agnieszka Sorensen at the plant to rare isotope beams in Michigan. The new experiment not only serves as a guide to where to look for this point, but it has also revealed which particle properties can offer the best clues as it exists, she says.

Claudia Ratti at the University of Houston in Texas says many scientists have been enthusiastic about anticipating this new analysis because it provided a precision that previously measurements could not achieve, and did it for part of the phase diagram where theoretical calculations are notoriously difficult. Recently, several predictions for the critical point location are converged, and the challenge for experimental will be to analyze the data for the even lower collision energy that correspond to these predictions, she says.

A clear detection of the critical point would be a generational breakthrough, says Dong. This is partly due to the fact that the strong force is the only basic force that physicists suspect has a critical point. In addition, this strength has played a significant role in the design of our universe: the controlled properties of hot and dense fabric created right after the Big Bang, and it still dictates the structure of neutron stars. DONG says that collider experiments like the new one could help us understand what is going on inside these exotic cosmic objects when we have completed the strong power phase diagram.