Found: the elusive pentaquark particle | Science| In-depth reporting on science and technology | DW | 16.07.2015
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Found: the elusive pentaquark particle

It sounds like a made-up Wiccan expression, but it's cold, hard science: CERN scientists in Switzerland have discovered a pentaquark particle while using the Large Hadron Collider.

It was really more of a coincidence. The physicists at CERN, close to Geneva, Switzerland, weren't looking for the pentaquark particle. They used their Large Hadron Collider to let protons, well, collide at nearly the speed of light. The things that happen and the particles that are created during that process are continuously recorded by highly precise detectors. At one point, these detectors recorded unusual signals. CERN experts say they arrived at the conclusion that they had found a pentaquark by eliminating all other options.

The CERN-scientists kept their discovery to themselves until they were completely sure and had run thorough analyses. After all, physicists have been chasing after this particle, which until now had only been known in theory for years.

Several times in the past, researcher teams have announced that they finally found proof for pentaquarks, but each time, their results were refuted or recanted. That's why it's easy to believe scientists are just crying wolf. And all this hoopla for a tiny particle that disintegrates almost right after it's formed.

So what exactly is a pentaquark?

To understand this, we have to take quite a back: visible matter, whether it makes up humans, animals or plants, consists of different matter particles. These in turn are made up of just a few elementary particles like quarks or leptons.

On top of that, there are particles which are very ephemeral and disintegrate quickly. These particles arrive on Earth via cosmic radiation - or they can be produced artificially by a particle collider. This is what happened at CERN.

In the Large Hadron Collider, the pentaquark was created when protons bumped up against each other at high speed. The particle was short-lived and was actually made up of five quarks - or rather four quarks and one anti-quark. It's not yet clear how exactly these quarks were set up in relation to each other.

Wow! Is this a milestone?

Not really. But it is finally proof for the exotic particle's existence. So far, none of the scientists who predicted the existence of this particle in theory could bring proof. And some of them had been at it for a frustratingly long time.

It took the world's largest particle collider to ferret out the elusive pentaquark. It's another success for CERN, where the Higgs particle was discovered in 2012. The expensive particle collider is clearly worth it. The pentaquark represents another puzzle piece in particle research, which helps us learn more about our universe.

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