LHC reports discovery of its first new particle

The LHC has been built to investigate the fundamental building blocks of nature

The Large Hadron Collider (LHC) on the Franco-Swiss border has made its first clear observation of a new particle since opening in 2009.

It is called Chi_b (3P) and will help scientists understand better the forces that hold matter together.

The as-yet unpublished discovery is <link> <caption>reported on the Arxiv pre-print server</caption> <url href="http://arxiv.org/abs/1112.5154" platform="highweb"/> </link> .

The LHC is exploring some of the fundamental questions in "big physics" by colliding proton particles together in a huge underground facility.

Detail in the sub-atomic wreckage from these impacts is expected to yield new information about the way the Universe is constructed.

The Chi_b (3P) is a more excited state of Chi particles already seen in previous collision experiments, explained Prof Roger Jones, who works on the Atlas detector at the LHC.

"The new particle is made up of a 'beauty quark' and a 'beauty anti-quark', which are then bound together," he told BBC News.

"People have thought this more excited state should exist for years but nobody has managed to see it until now.

"It's also interesting for what it tells us about the forces that hold the quark and the anti-quark together - the strong nuclear force. And that's the same force that holds, for instance, the atomic nucleus together with its protons and the neutrons."

The LHC is designed to fill in gaps in the Standard Model - the current framework devised to explain the interactions of sub-atomic particles - and also to look for any new physics beyond it.

In particular, it is using the collisions to try to pin down the famous Higgs particle, which physicists hypothesise can explain why matter has mass.

Discoveries such as Chi_b (3P) are an important part of this quest because they add to the wider background knowledge, says Prof Jones, from Lancaster University, UK.

"The better we understand the strong force, the more we understand a large part of the data that we see, which is quite often the background to the more exciting things we are looking for, like the Higgs.

"So, it's helping put together that basic understanding that we have and need to do the new physics."

Prof Paul Newman, from the University of Birmingham, added: "This is the first time such a new particle has been found at the LHC. Its discovery is a testament to the very successful running of the collider in 2011 and to the superb understanding of our detector which has been achieved by the Atlas collaboration already."

And Andy Chisholm, a PhD student from Birmingham who worked on the analysis, said: "Analysing the billions of particle collisions at the LHC is fascinating. There are potentially all kinds of interesting things buried in the data, and we were lucky to look in the right place at the right time."