Scarcely three weeks ago, it was reported that the Relativistic Heavy Ion Collider (RHIC) at the Brookhaven National Laboratory had achieved the all time (laboratory) high temperature record of 4 trillion degrees Centigrade. [SciTechStory: Taking the temperature of the Big Bang + milliseconds] The significance was that in colliding atoms of gold and producing such high temperatures they discovered that instead of the expected gas, a plasma (liquid, a veritable soup) of particles was created. Now, in another study completed at the same facility with the RHIC STAR detector, an international team of scientist is reporting some of the first particle discoveries. In this case, it’s antimatter, the heaviest known antinucleus, and the first containing an anti-strange quark. ? You ask. It’s a new frontier of physics, they’ll answer.

It certainly is new. Although antimatter has been known for some time, scientists haven’t met many. It’s also known that in the seconds after the Big Bang there must have been a lot of antimatter. So where has it gone? Why do we have the universe that we know today, the one built out of matter and not antimatter? You can’t even begin to address such questions until you know more about what antimatter looks like and how it behaves. That’s what makes this kind of experiment and analysis important. It is, in fact, a new way to look at the cosmos and its fundamental properties.

This experiment produced not just “antimatter” but some of its components – a much more important step. Included in the mix were an antiproton, an antineutron, and an anti-Lambda particle – plus, and this was extraordinary, there was also an antinucleus containing an anti-strange quark.

OK. Some explanation.

The everyday atomic nucleus we know is made of protons and neutrons (which contain quarks). Quarks are the most fundamental of particles. They combine into larger stable particles (hadrons) – including protons and neutrons. There are six types of quarks (known as flavors): up, down, charm, strange, top, and bottom. For each of these there is (in theory) an antiparticle, an antiquark – for example, an anti-strange quark. That’s a strange quark that differs only in having an opposite sign (for electric charge). All of the normal quarks have been seen in particle accelerators, but not the antiquarks, until now.

The standard Periodic Table of Elements is ordered according to the number of protons. Physicists use a more complicated, three-dimensional table that also contains information on the number of neutrons, which vary for isotopes of an element, and a quantum number that identifies “strangeness” – the presence of strange quarks. Nuclei that contain one or more strange quarks are called hypernuclei. As a matter of representation, hypernuclei appear above the plain of the chart. The new discovery of this study is the strange antimatter nucleus with an antistrange quark, which means there is an antihypernucleus below the plain of the chart.

If all this sounds rather symmetric and structural – it is. It may be, in fact, the fundamental structure of everything. In the RHIC collisions quarks and antiquarks are produced in what looks like equal numbers. Since the RHIC collision is very close to the conditions of the Big Bang, it’s assumed that there too the quarks and antiquarks should be equal in number. The question still hangs out there – why do we see matter but not antimatter in the present day universe?

“Understanding precisely how and why there’s a predominance of matter over antimatter remains a major unsolved problem of physics,” said Brookhaven physicist Zhangbu Xu, another one of the lead authors. “A solution will require measurements of subtle deviations from perfect symmetry between matter and antimatter, and there are good prospects for future antimatter measurements at RHIC to address this key issue.”

[Source: Brookhaven National Laboratory]

In the coming years, as the RHIC is upgraded and more experiments can be run at higher speeds (temperatures), it is hoped that discoveries will be made of even heavier anti-nuclei. At each step, the theorists can run to the equations and probe for matches between what was expected and what actually shows up in the collider. For example, it is predicted that strange nuclei around double the mass of the one just discovered should be particularly stable (that is, exist for more than a femtosecond).

Ultimately, through these experiments the scientists are hoping to come to some analytical conclusions about the properties and behavior of antimatter. It’s like looking into a strange (pun intended) new world, and trying to guess what, if any, connection it has with the world you know.