Hints of Mysterious Particle Detected in Big Bang 'Soup'

An ordinary proton or neutron (foreground) is formed of three quarks bound together by gluons, carriers of the color force. Above a critical temperature, protons and neutrons and other forms of hadronic matter "melt" into a hot, dense soup of free quarks and gluons (background), the quark-gluon plasma.

(Image credit: Lawrence Berkeley National Laboratory)

Hints of a mysterious particle that has been long suspected to exist but has never been spotted are being revealed in a new experiment.

So far, the elusive particles, called extra-heavy strange baryons, haven't been seen directly, but they are leaving tantalizing hints of their existence.

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The particles were created during an experiment conducted inside the Relativistic Heavy Ion Collider (RHIC), an atom smasher at Brookhaven National Laboratory in Upton, New York. There, scientists created a soupy concoction of unbound quarks — the subatomic particles that make up protons and neutrons — and gluons, the tiny particles that bind quarks together and carry the strong nuclear force. Physicists think this quark-gluon plasma is similar to the primordial soup that emerged milliseconds after the universe was born.

Enter the RHIC experiment, which accelerates gold nuclei, or the protons and neutrons in a gold atom, to nearly the speed of light, and then crashes these gold ions into one another. The resulting collisions can raise the temperature inside the collider to a mind-boggling 7.2 trillion degrees Fahrenheit (4 trillion degrees Celsius), or 250,000 times as hot as the heart of the sun. The huge burst of energy released during the collision melts the protons and neutrons in the nuclei into their smaller components, quarks and gluons.

In this soupy plasma of quarks and gluons, Mukherjee and his colleagues noticed that other, more common, strange baryons were freezing out of the plasma at a lower temperature than would ordinarily be predicted. (There are several types of strange baryons.) The scientists hypothesized that this freezing-out occurred because the plasma contained as-yet-undiscovered hidden particles, such as hadrons composed of extra-heavy strange baryons.

Now, the team is hoping to create a map of how different types of matter, such as quark-gluon plasma, change phases at different temperatures. Just as the chemical symbol H20 represents water in the form of a liquid, ice or steam depending on the temperature and pressure, the subatomic particles in an atom's nucleus take different forms at different temperatures. So, the team is hoping the new results could help them to create a map of how nuclear matter behaves at different temperatures.

Tia is the editor-in-chief (premium) and was formerly managing editor and senior writer for Live Science. Her work has appeared in Scientific American, Wired.com, Science News and other outlets. She holds a master's degree in bioengineering from the University of Washington, a graduate certificate in science writing from UC Santa Cruz and a bachelor's degree in mechanical engineering from the University of Texas at Austin. Tia was part of a team at the Milwaukee Journal Sentinel that published the Empty Cradles series on preterm births, which won multiple awards, including the 2012 Casey Medal for Meritorious Journalism.