News in Science

Hadron collider on holiday

Seven months after its scientists made a landmark discovery that may explain the mysteries of mass, Europe's top physics lab will take a break from smashing invisible particles to recharge for the next leap into the unknown.

The cutting-edge facilities at the European Organisation for Nuclear Research (CERN) will go offline from this weekend for an 18-month upgrade.

A vast underground lab straddling the border between France and Switzerland, CERN's Large Hadron Collider (LHC) was the scene of an extraordinary discovery announced in July last year.

Its scientists said they were 99.9 per cent certain they had found the elusive Higgs Boson, an invisible particle without which, theorists say, humans and all the other joined-up atoms in the universe would not exist.

The upgrade will boost the LHC's energy capacity, essential for CERN to confirm definitively that its boson is the Higgs, and allow it to probe new dimensions such as supersymmetry and dark matter.

"The aim is to open the discovery domain," says Frederick Bordry, head of CERN's technology department.

"We have what we think is the Higgs, and now we have all the theories about supersymmetry and so on. We need to increase the energy to look at more physics. It's about going into terra incognita (unknown territory)."

Theorised back in 1964, the boson, also known as the God Particle, carries the name of a British physicist, Peter Higgs.

He calculated that a field of bosons could explain a nagging anomaly: Why do some particles have mass while others, such as light, have none?

Supersymmetry

That question was a gaping hole in the Standard Model of particle physics, a conceptual framework for understanding the nuts-and-bolts of the cosmos.

One idea is that the Higgs was born when the new universe cooled after the Big Bang some 14 billion years ago.

It is believed to act like a fork dipped in honey and held up in dusty air.

Most of the dust particles interact with the honey, acquiring some of its mass to varying degrees, but a few slip through and do not acquire any. With mass comes gravity - and its pulling power brings particles together.

Supersymmetry, meanwhile, is the notion that there are novel particles that are the opposite number of each of the known particle actors in the Standard Model.

This may, in turn, explain the existence of dark matter - a hypothetical construct that can only be perceived indirectly via its gravitational pull, yet is thought to make up around 25 per cent of the universe.

Billions of collisions

Bordry says it was originally planned to have a long shutdown in 2012, but "with the perspective of discovering the boson, we pushed the long shutdown back by a year".

Over the past three years, CERN has slammed protons together more than six million billion times.

Five billion collisions yielded results deemed worthy of further research and results from only 400 threw up data that paved the road to the Higgs Boson.

Despite the shutdown, CERN's researchers won't be taking a breather, as they must trawl through a vast mound of data.

"I think a year from now, we'll have more information on the data accumulated over the past three years," says Bordry. "Maybe the conclusion will be that we need more data."

Last year, the LHC achieved a collision energy level of eight teraelectron volts, an energy measure used in particle physics - up from seven in 2011.

After it comes back online in 2015, the goal is to take that level to 13 or even 14, with the LHC expected to run for three or four years before another shutdown.