Upgrading the LHC

by Nicholas Mee on March 12, 2013

On 11th February the Large Hadron Collider (LHC) at CERN, the European particle physics laboratory near Geneva, was shut down for a complete overhaul. The huge machine will be out of action for almost two years. The restart is scheduled for December 2014. Engineers are working around the clock to meet this deadline. When the accelerator comes back on line it will be colliding protons at its full design energy of 14 TeV per beam, almost double its previous record-breaking energy.

This Masquerade?

Researchers will not be taking it easy while the LHC is upgraded. The LHC has already generated a huge amount of data that is being pored over in the search for new physics. On 4th July 2012 CERN made the big announcement that the LHC had found very strong evidence for a new particle that looked very much like the long anticipated Higgs boson. Since then at least two and a half times as much data has been collected and physicists are examining the results to see whether the new particle really is the Higgs or whether it might be something else masquerading as the Higgs. At a conference today (14th March 2013) in Moriond in Italy physicists announced that all the evidence very strongly suggests that the new particle does have the correct characteristics to be identified as the Higgs boson. The most important of these is that it has zero spin. No other fundamental particle with zero spin has ever been discovered. The results of further analyses are expected within the next few months.

What else has the LHC been up to?

The LHC has been doing a lot more than just searching for the Higgs boson. Protons, neutrons and all other particles that feel the strong nuclear force are referred to collectively as hadrons. These particles all consist of quarks and antiquarks bound together in one of two ways. The first type are formed of a quark bound to an antiquark. This type of hadron includes particles known as pions that were first identified as long ago as 1947. The second type of hadron is formed of three quarks bound together. These includes particles such as protons and neutrons. (Three antiquarks may also bind together to form particles such as antiprotons and antineutrons.)

Exotic Physics

The strong force which holds these hadrons together is explained by a theory called quantum chromodynamics (QCD). According to QCD, quarks and antiquarks are bound together by exchanging particles known as gluons. (Gluons get their name because they provide the glue that holds the quarks together.) QCD allows the possibility that quarks and gluons might combine in other ways to form hadrons. Any hadrons with a different structure to the two possibilities mentioned above are known as ‘exotics’. Physicists have searched for exotics for many years, but so far their existence has not been confirmed. However, there are signs that the LHC may have discovered the first ‘exotic’. It is a particle that appears to be formed of four subcomponents – two quarks and two antiquarks. Watch out for more details about this exotic breakthrough.

Super Physics

Physicists are also combing the data for the first hints of supersymmetry. If Nature really is supersymmetric then there will be many new particles awaiting discovery by the LHC. A tantalizing glimpse of any of these particles would be heralded as an even greater achievement than the discovery of the Higgs. It would be seen as the first sign that string theory is not simply pie in the sky. It might also offer the possibility of explaining the origin of dark matter – the mysterious stuff that seems to form most of the material in the universe.

Further Information

There is much more information about quarks, gluons and the strong force in my book
Higgs Force:

For more about dark matter, see my article Most of the Universe is Missing!:


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