Packed Lunch and the last crusade

Large Hadron Collider

Large Hadron Collider


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Though few of us understand it, particle physics and the essence of the universe remain among the most fundamentally fascinating topics in science. That much was obvious from the standing room only, extra packed Packed Lunch when Jonathan Butterworth, Professor of Physics at UCL, came to talk about CERN, home of the Large Hadron Collider (LHC).

Based in Geneva, Switzerland, CERN (Conseil Européen pour la Recherche Nucléaire or the European Organisation for Nuclear Research, in case you’d ever wondered) was set up in 1954 to re-establish European science after the Russians and Americans took the lead post-World War 2.  At that time, particle physics was understandably seen as a key science for many reasons, not least military applications.

Although much of what CERN does is purely in the pursuit of knowledge, it was set up with the understanding that if you don’t have academic physics you don’t get the more practical kinds. As Butterworth put it, being at the cutting edge of science “pulls a lot of stuff behind it”. Lest we forget, work at CERN has given us, among other things, the World Wide Web, superconducting Rutherford cables and improved medical imaging technologies.

CERN’s centrepiece is the Large Hadron Collider, which does exactly what it says on the tin. It’s very large (27 kilometre long to be exact) and smashes Hadrons (protons and neutrons to you and me) together. Essentially, said Butterworth, it’s a “big bang machine”.

The universe started with particles of high energy colliding together and emitting other particles as a result. This led to everything we see today. Thus, said Butterworth, the physics CERN is studying is, in a sense, “the only physics in the universe”.

This brings us to the most famous of CERN’s experiments, the search for the Higgs boson or ‘God’ particle as it’s been dubbed. The standard model of particle physics is that atoms are made up of 12 fundamental particles including quarks (the stuff protons and neutrons are made of) and electrons. These interact via four forces: gravity, electromagnetism (photons i.e. light), gluons (which hold quarks together) and what’s termed ‘Ws and Zs’ (weak forces).

According to Butterworth this model is a “beautifully symmetrical theory” that allows us to predict a lot about how the universe works. The trouble is it only works if everything has no mass, which makes reality a bit of an issue. The Higgs boson is a way to resolve this.

Of course, there’s irony in the fact that this fundamental theory rests on a particle that we don’t even know exists. Elements of the Higgs-based theory have been detected but the LHC is the first scientific instrument with a range capable of proving the existence of the Higgs.

That in itself is a big ask given – that you are looking for one thing amongst thousands of particle collisions taking place at the same time – not to mention the fact that you don’t know what exactly you’re looking for.

If the Higgs is there and turns out to be a heavy, it will fly off in a collision and decay to different particles. If it is lighter it will decay to two quarks. Picking them out will be a problem but this is precisely what Butterworth’s research is all about.

He works on the ATLAS project, one of several detectors in the LHC used to look for the Higgs (among other experiments). Butterworth said it was like a massive camera synchronised to track collisions taking place once every 40 nanoseconds and capable of clicking the shutter at the right moment. There’s an element of luck of course, particularly as any ‘picture’ captured is likely to pick up several collisions at a time.

It’s a massive and expensive undertaking. The LHC’s budget is €1 billion and the scale of the project is something no single institute or country could deliver alone. CERN is funded by 20 European states, with researchers from many more countries involved.

That level of teamwork is astounding – ATLAS alone involves 50 different laboratories from many different countries making parts for the same device. But it works and fosters a sense of collaboration as well as competition, said Butterworth, with everyone relying on each other and everyone desperate for the data produced.

There are some 1500 people working at CERN and 10 times that number visiting and collaborating. Butterworth described it as a “geek paradise”, a scientific city that’s grown on the outskirts of Geneva.

“It’s one of the few places in the world where new physics is being done,” he said, “Not the stuff in the textbooks, but new things being done now. It’s incredibly inspiring and driving people to see that physics is important.”

In fact, it doesn’t necessarily matter if they find the Higgs or not, he said. What the experiment is really about is learning more about how the fundamental particles and forces interact (specifically ‘electroweak symmetry breaking’ – I’ll leave you to listen to the podcast for an explanation of that).

It’s not a search for the ‘God particle’ said Butterworth, but more like a quest for the Holy Grail: what you learn on the journey is more important that what you find at the end.

You can read more about this session on Jon Butterworth’s blog.

Mun-Keat Looi is a Science Writer at the Wellcome Trust.

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