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Inside the search for the God particle Add to ...

Smashing particles together is the best way physicists have of learning what the world is made from, and they have constructed increasingly complex and powerful colliders to identify fundamental particles that are the building blocks of matter.

The latest and most expensive, the $9.5-billion Large Hadron Collider on the French-Swiss border, will eventually accelerate protons to 99.9999991 per cent of the speed of the light, and recreate conditions that existed in the earliest moments of the universe, one trillionth of a second after the Big Bang.

Physicists aren't sure what they will find by analyzing the debris, but the possibilities include miniature black holes, new dimensions and particles that have never been seen before.

However, one of the goals is to find a particle called the Higgs boson, nicknamed the God particle. It is central to modern physics, but has never been detected.

The Large Hadron Collider is the most ambitious particle physics experiment in history, but it is building on the discoveries of machines that in turn were the greatest of their time.

In the first pioneering experiment nearly 100 years ago, New Zealand physicist Ernest Rutherford revealed the structure of the atom - a heavy nucleus at the centre with electrons whizzing around it.

"With the sort of energy Rutherford had you could see the nucleus inside the atom, but you couldn't see what was inside the nucleus," says Robert Orr, one of several dozen Canadian scientists and graduate students involved in the LHC.

Higher and higher energy colliders allow physicists to "see" smaller and smaller things, Dr. Orr says.

Increasingly powerful machines revealed what was inside the nucleus: protons and neutrons.

Then came discoveries about what was inside protons and neutrons, namely quarks, which can be held together with particles called gluons.

There is a second category of particle, called leptons, which includes electrons and muons.

Physicists explain how these various kinds of fundamental particles can be put together to make matter as we see it with a suite of theories called the Standard Model.

It offers an unproven explanation for why all these tiny particles have mass, hypothesizing that something called a Higgs field permeates the universe.

The Higgs field is invisible, but has been compared to molasses because it slows particles down.

"If the Higgs field didn't exist, particles would all be mass-less and would travel around all the time at the speed of light," Dr. Orr says.

In theory, if you put energy into this Higgs field, you can create particles called Higgs bosons, he says.

That, in simple terms, is what the Large Hadron Collider is trying to do. It is checking to see if the Standard Model is right.

Canadians have helped design and build one of four detectors that will help them look for the Higgs particle among the debris once the protons start colliding.

The ATLAS detector is as high as a five-storey building and weighs 7,000 tonnes, said Carleton University physicist professor Gerald Oakham.

The detector will take 90 million measurements at a rate of 600 million times a second.

Isabel Trigger is a physicist at TRIUMF, Canada's national laboratory for particle and nuclear physics, housed at the University of British Columbia, and ATLAS-Canada physics co-ordinator.

She is confident the detector will spot the Higgs boson, if it does, in fact, exist.

"We are pretty confident we will be able to see it or anything else that is doing its job and is more interesting."

OFF WITH A BANG

The Large Hadron Collider (LHC) will accelerate two beams of protons around a 27 km ring and smash them together at 99.99% the speed of light. Its 9,300 magnets will guide the particles through a vacuum at minus 271 degrees, recreating conditions in deep space moments after the Big Bang.

FOUR EXPERIMENTS

Protons - produced by stripping electrons from hydrogen atoms - will smash together at four collision points, monitored by complex devices

THE ATLAS PROJECT

Canada has contributed $30-million and more than 150 scientists, mainly to the ATLAS project

ATLAS will search for elusive Higgs boson, a subatomic particle that is thought to give mass to all matter. Key missing particle could link electromagnetic, strong and weak nuclear forces of standard model with gravity.

Scientific staff: 1,700+

STEP BY STEP

Particles injected in the smaller machines arrive at the SPS

Particles are transferred to the LHC, forming two beams travelling in opposite directions

Particles accelerated to near the speed of light and collide at four points where the two rings intersect

ALICE

Will study quark-gluon plasma, a form of matter believed to have existed 10-25 seconds after the Big Bang, 14 billion years ago Scientific staff: 1,000+

CMS

Will search for new particles using magnetic field 100,000 times stronger than Earth's

Scientific staff: 2,000+

LHCb

Will study 'beauty' or b-quarks and investigate differences between matter and antimatter

Scientific staff: 650

SOURCE: CERN

 

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