Scotland

Homing in on the Higgs

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Media captionBBC Scotland's Ken Macdonald searches for the most elusive particle in the universe

Lots of people worry about why they weigh so much. But have you ever wondered why you weigh anything at all?

Physicists think their Standard Model provides the answer: a fundamental particle that gives all other matter its mass.

The trouble is, after almost 50 years it is still just a theory: the Higgs Boson is proving to be the most elusive particle in the Universe.

If it does exist, Scotland will be able to claim its share of the glory.

Image caption Professor Peter Higgs of Edinburgh University proposed his concept in 1964

Professor Peter Higgs of Edinburgh University proposed his concept of a mass-giving particle in 1964.

So it is fitting that dozens of scientists from Scottish universities are working at the European nuclear research centre Cern as part of a massive international collaboration dedicated to finding the Higgs.

One hundred metres beneath Cern - which straddles the Switzerland-France border - lies the biggest machine in the world: the Large Hadron Collider (LHC).

Professor Tony Doyle of Glasgow University is one of the researchers working on the LHC.

He says it "accelerates protons up to seven trillion electron volts".

"That ... is then converted into new matter," he says.

Matter which he expects to contain the Higgs.

Think of the LHC as a kind of time machine.

By accelerating a stream of protons to almost the speed of light, then colliding it with another proton stream travelling just as fast in the opposite direction, it creates the conditions which existed just one-billionth of a second after the Big Bang.

Suddenly, we are looking back 13.7 billion years.

So how close is it bringing us to finding the Higgs Boson? It appears the net is tightening.

The research teams have methodically eliminated all but the area where the Higgs is mostly likely to be.

Image caption Dr Samir Ferrag said there was only "one room" left to search for the Higgs

Dr Samir Ferrag is another Glasgow University researcher at the LHC.

He says we should imagine the search as a house with exactly sixty rooms.

"We open the doors of each room and say 'the Higgs is not here, the Higgs is not here, the Higgs is not here'.

"Today we are left with one room, and we should be able to open the door and decide if the Higgs exists - or doesn't exist - within the next few months."

The huge international effort at the LHC would be impossible without a massive computing effort.

Cern's computer centre has the power of about 50,000 desktop PCs.

But that's not nearly enough: Atlas, which is just one of the four big detectors ranged around the LHC's 27 km circular tunnel, has already generated enough data to fill a stack of DVDs 12 km high.

So the LHC's Grid project distributes computing jobs to hundreds of thousands of other processing units worldwide.

Dr Philip Clark leads Edinburgh University's team at Cern.

Questions to be answered

He says it is especially important because researchers are not just recording collisions - they are simulating what Higgs events are likely to look like.

"We're currently simulating about two billion events," he says, "and each event takes about 20 minutes."

He adds: "It would take you maybe 75,000 years to do this on one computer."

There is the niggling possibility that Dr Ferrag's last room will be opened and will be empty - that Peter Higgs's model was elegant but ultimately wrong.

However the consensus is that the Higgs is there to be found.

And if not there are plenty of other questions to be answered.

Questions like, how many dimensions are there? Why can't we find most of the Universe? And where has all the antimatter gone?

Enough to keep the LHC busy for, if not 13.7 billion years, then certainly a while yet.