'Little Bang' creates cosmic soup

Quarks were allowed to roam free (Cern impression)

By BBC News Online science editor Dr David Whitehouse

Scientists have created what they describe as a "Little Bang" inside which are the conditions that existed a thousandth of a second after the birth of the Universe in the so-called Big Bang.

In doing so, they have made a form of matter that has not existed for 15 billion years.

The experiments were part of the Heavy Ion programme

It is called a "quark-gluon" soup or plasma. By studying its properties, and the laws it obeys, scientists will learn more about how the Universe developed during one of its formative phases.

In short, scientists believe the reason why there are stars, galaxies and indeed planets and people is because of the properties of the quark-gluon plasma.

YOUNG, FREE AND SINGLE

Quarks normally exist only as couples or threesomes

Gluons handcuff quarks together

Together, quarks and gluons make up bigger particles such as protons or neutrons

Quark-gluon soup is a sort of brief particle pre-nuptial state

The breakthrough is the result of several experiments by researchers from 20 countries working on the Heavy Ion Programme at the Cern nuclear research centre in Geneva, Switzerland.

The scientists say they have produced compelling evidence for the new state of matter in which quarks roam free, instead of being held together by gluons to make complex particles such as protons and neutrons.

Building blocks

Quarks are thought to be one of the fundamental building blocks of matter.

In the Universe we know today, the particles come in pairs or threes. But when the Universe was more energetic, in its earliest moments, things were probably different.

Current theory predicts that quarks must have once been single and free to move about before they joined together to form matter as we see it now.

The results from several experiments had to be combined

But until Cern's success, such a state of matter has not been confirmed experimentally.

Professor Luciano Maiani, Cern's Director General, said: "The combined data coming from the seven experiments on Cern's Heavy Ion Programme have given a clear picture of a new state of matter.

"This result verifies an important prediction of the present theory of fundamental forces between quarks."

He added: "It is also an important step forward in the understanding of the early evolution of the Universe. We now have evidence of a new state of matter where quarks and gluons are not confined. There is still an entirely new territory to be explored."

Staggering properties

The crucial data was obtained by colliding ionised lead atoms to create microscopic explosions that, although very small, have very high concentrations of energy. Such "Little Bangs" have staggering properties, being at a temperature of two-million-million degrees and 20 times denser than the nucleus of an atom.

These high energies, it was hoped, would break down the forces which confined quarks inside more complex particles.

Computer-constructed tracks produced by particles after a collision

This is what the scientists appear to have witnessed. The high-energy lead ions were crashed into targets inside seven different detectors. The collisions created conditions that have never before been reached in laboratory experiments.

The data from the collisions provides compelling evidence that a new state of matter has been created. It has many of the characteristics of the theoretically-predicted quark-gluon plasma.

Creating the new state of matter is only a beginning for the Cern researchers. The next step is to study how it behaves at different temperatures and densities. This will allow the scientists to probe key moments in the evolution of the Universe of stars and galaxies from the Universe of quarks and gluons.