It's the Shakespeare question of science, but experts believe we are close to finding one of the universe’s best kept secrets - the ‘Higgs Boson’, if it actually exists.
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| Large Hadron Collider. Credit: CERN |
One of the aims of the Large Hadron Collider at CERN is to map the dark secrets of the universe, including an illusive particle considered to be responsible for giving mass to all known matter - the Higgs Boson. If it’s not discovered, much of our entire understanding of physics will need to be re-written.
One of Australia’s leading physicists Professor Geoffrey Taylor visited ANSTO recently to shed some light on this mission and explain the role of the ATLAS experiment in finding what’s being referred to as the ‘God particle’.
“There’s a saying in physics that one person’s discovery is another person’s background,” Professor Taylor says. Just when science was unlocking one mystery, and handing out Nobel Prizes, like for the discovery of the atom, along comes a new wave of science and a new set of challenges.
Professor Taylor knows a thing or two about this in the world of particle physics. He is a member of the ATLAS collaboration and Centre Director at the ARC Centre of Excellence for Particle Physics at the Terascale (CoEPP) in Melbourne.
His work is helping put Australia on the map with a number of key collaborations now established with the leading physics institute in the world – CERN. It’s at CERN in Switzerland that a lot of the ground breaking work is currently taking place, but credence should be given to some discoveries in other scientific fields.
Our current understanding of the universe
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| The dark matter Illustrates our current understanding of what the universe is made up of .4 percent of this is what we already know. |
Cosmology has played its part of late. A revolution in this field is turning some of our established theories of the universe on their head. As Brian Schmidt’s Nobel Prize from last year attests to, we now know that not only is the universe expanding, its expansion is accelerating.
An even more outrageous discovery compounds all this. Science is slowly getting its head around the atom and all its interactions, but we now know that these elements only make up a fraction of the universe. In fact it’s less than 5 per cent. The rest of the universe is made up of other stuff.
Professor Taylor says this data coming in from cosmology is fantastic and is now having a big impact on particle physics.
“We know that all the protons and electrons are built from the standard model of physics and held together by electromagnetism. Unfortunately, this only explains about 4 per cent of the universe. It explains most things on earth, but the rest of the universe is made up of other stuff.”
It’s been observed that 70 per cent of the universe is made up of dark energy, with dark matter making up 25 per cent. But where does this fit in with CERN and the Higgs Boson?
The Standard Model and the Higgs Boson
Professor Taylor who was visiting the Australian Nuclear Science and Technology Organisation (ANSTO) as part of a Distinguished Lecture series says that the current rules of physics are dictated by the Standard Model. It hypothesizes that everything in the Universe was made from twelve basic building blocks and governed by four fundamental forces.
“The particle physics model explains pretty much everything about the quiet universe we live in through the forces of a mathematical symmetry that explains how all these particles interact.
“Really, we’re a bit sick of it as experimentalists, because all we seem to do for the last 30 years is say yep, you guys are right again,” Professor Taylor laments.
This is where it gets complicated. Professor Taylor says the mathematical symmetry of the electroweak interaction in the Standard Model, which is the description of two of the four known fundamental interactions of nature, is beautiful but new research is showing it’s not quite right. There is something missing, which could explain the masses of objects.
That was until a couple of bright physicists named Higgs, Brout and Englert came up with the theory that it maintains its symmetry, but the ground state the universe is in has a broken symmetry, which gives rise to this mass.
“When the universe cooled down, it fell into a ground state – a vacuum state – which is not symmetrical, and this is the process that Higgs is now famous for.
“It could be Higgs, or it could be something else. Either way the Large Hadron Collider (LHC) has to find something,” Professor Taylor says.
The ATLAS experiment
This is where the ATLAS experiment comes in at CERN. ATLAS is one of the seven particle detector experiments constructed at the LHC in Switzerland. It’s a fairly large instrument stretching about 55 metres in length and 75 meters high.
It’s believed only moments after the Big Bang, the phenomenon was many times in magnitude the temperature of the centre of what the sun is today. With the help of the ATLAS detector scientists are working on the biggest physics experiment in the world to try and understand the Higgs Boson.
“We’re currently probing interactions at this precise moment, just after the Big Bang and the beginning of the universe well before electron magnetism dominated and before the atom regime.”
The problem is, as Professor Taylor laments, we’re talking about a needle in a hay stack, in a hay stack, in a hay stack. These particles are believed to exist for less than a septillionth of a second, but scientists are confident they have the right tool to tackle this problem. The Collider is able to generate significant amounts of energy and should be able to find the Higgs Boson, if it exists.
“The aim of the game is to hit 1013 events so that we can create one Higgs Boson and get the people operating the machines to give us more, and more of these events in as shorter period as possible.”
And of course it's a team effort. The success of ATLAS in finding smoking guns that come from each interaction is thanks to the contribution of hundreds of organisations and countries.
ANSTO played its minor part.
"The work done by Melbourne, Sydney (universities) and ANSTO on particle radiation properties contributed to the building of the inner detector, which is about 6 metres long.
"The wheels – which are the silicon detectors – represent about 70 square meters of silicon and each of the resolutions are about 16 microns, so about a sixth of the thickness of a human hair.
"Inside each detector is about 80 millions channels of electronics. So this is an order of magnitude bigger than anything that had been done before," Professor Taylor said.
Where in the world is the Higgs Boson?
Last year was a dry run for the Collider after a breakdown in 2008 in its first attempt at going online.
“The press said it was a helium leak, and it was – about a tonne and a half of liquid helium in a couple of hundred milliseconds moved 40 magnets around worth billions of dollars.
“It was created by a spark and when you’ve got 12,000 amps of current going through it can be quite damaging and it filled up the vacuum vessel which goes for about 8km with soot.
The main goal second time around was to calibrate the detector by using the data it received to reconfirm the Standard Model. So far, mission accomplished.
All the results from their experiments have now been analysed in a landmark year, which leaves the door open for big things in 2012.
Professor Taylor believes CERN is ready to answer this question once and for all, but knows there are some challenges ahead, for example, a little old thing called dark matter.
“We have a situation that with every beam crossing, that’s one every 25 nanoseconds, there were 18 interactions – 18 protons struck each other. The one we thought was interesting was the particles we wanted to track were among all the white haze. We can’t just tell all the other particles to be quiet,” he said.
The other challenge for the scientists collaborating on the experiment is dealing with the massive amounts of data, both to store and process.
“If there is something interesting we have to try and read it out. The problem is we have high rates and big events [interactions]. The ATLAS detector produces about 5 or 6 petabytes of data a year. We haven’t had to deal with that sort of data before.
The stage is set for a major breakthrough. While no definitive results have been found, if the Higgs is out there, the collaborative teams at CERN believe they’re on the right track and its discovery could be right around the corner.
Published: 13/04/2012