Thursday, July 5, 2012

The 'God' particle



The 'God' particle is a name given by the media to the Higgs boson a sub-atomic particle theoretically predicted by The Standard Model of particle physics to give all matter mass.

Scientists at the CERN research centre near Geneva, Switzerland, on Wednesday unveiled their latest findings in their search for the Higgs boson, a subatomic particle key to the formation of stars, planets and eventually life after the Big Bang 13.7 billion years ago.

WHAT IS THE HIGGS BOSON?

The Higgs is the last missing piece of the Standard Model, the theory that describes the basic building blocks of the universe. The other 11 particles predicted by the model have been found and finding the Higgs would validate the model. Ruling it out or finding something more exotic would force a rethink on how the universe is put together.

Scientists believe that in the first billionth of a second after the Big Bang, the universe was a gigantic soup of particles racing around at the speed of light without any mass to speak of. It was through their interaction with the Higgs field that they gained mass and eventually formed the universe.

The Higgs field is a theoretical and invisible energy field that pervades the whole cosmos. Some particles, like the photons that make up light, are not affected by it and therefore have no mass. Others find it drags on them as porridge drags on a spoon.


WHAT IS THE STANDARD MODEL? The Standard Model is to physics what the theory of evolution is to biology. It is the best explanation physicists have of how the building blocks of the universe are put together. It describes 12 fundamental particles, governed by four basic forces.

But the universe is a big place and the Standard Model only explains a small part of it. Scientists have spotted a gap between what we can see and what must be out there. That gap must be filled by something we don't fully understand, which they have dubbed 'dark matter'. Galaxies are also hurtling away from each other faster than the forces we know about suggest they should. This gap is filled by 'dark energy'. This poorly understood pair are believed to make up a whopping 96 percent of the mass and energy of the cosmos.

Confirming the Standard Model, or perhaps modifying it, would be a step towards the holy grail of physics - a 'theory of everything' that encompasses dark matter, dark energy and the force of gravity, which the Standard Model also does not explain. It could also shed light on even more esoteric ideas, such as the possibility of parallel universes.

CERN spokesman James Gillies has said that just as Albert Einstein's theories enveloped and built on the work of Isaac Newton, the work being done by the thousands of physicists at CERN has the potential to do the same to Einstein's work.

WHAT IS THE LARGE HADRON COLLIDER? The Large Hadron Collider is the world's biggest and most powerful particle accelerator, a 27-km (17-mile) looped pipe that sits in a tunnel 100 metres underground on the Swiss/French border. It cost 3 billion euros to build.
Two beams of protons are fired in opposite directions around it before smashing into each other to create many millions of particle collisions every second in a recreation of the conditions a fraction of a second after the Big Bang, when the Higgs field is believed to have 'switched on'.

The vast amount of data produced is examined by banks of computers. Of all the trillions of collisions, very few are just right for revealing the Higgs particle. That makes the hunt for the Higgs slow, and progress incremental.

WHAT IS THE THRESHOLD FOR PROOF? To claim a discovery, scientists have set themselves a target for certainty that they call "5 sigma". This means that there is a probability of less than one in a million that their conclusions from the data harvested from the particle accelerator are the result of a statistical fluke.

The two teams hunting for the Higgs at CERN, called Atlas and CMS, now have twice the amount of data that allowed them to claim 'tantalising glimpses' of the Higgs at the end of last year and this could push their results beyond that threshold.

Why is it important?

Essentially because it proves that our understanding of the basic workings of the universe is correct. If the Higgs boson didn’t exist, the Standard Model would be proved incorrect. Its importance led to the “God Particle” nickname. Physicist-cum-startup entrepreneur at PeerReach, Nico Schoonderwoerd says that it’s “A major milestone for the standard model,” as it validates all the work done, and all the money poured into its discovery.

Krassnigg elaborates: ”Picture the Standard Model as a car. Then you could imagine the Higgs boson to be, or provide, the wheels of that car. It had to be decided experimentally whether or not the car (our view of particle physics) actually is as we expected it to be, i.e., whether it actually does have wheels or not.

“For our car this is a question of central importance, since it determines what the car can do and how. While not having wheels would not have been a bad thing automatically – there are other fancier ways to move a car around -, it has now turned out that the wheels seem to be there and that this is the way the car moves.”


Where do we go from here?

So, if it is the Higgs boson that has been discovered, what does that mean for the future? CERN’s own announcement noted: ”Positive identification of the new particle’s characteristics will take considerable time and data. But whatever form the Higgs particle takes, our knowledge of the fundamental structure of matter is about to take a major step forward.”
Krassnigg continues his comparison of the Higgs boson with a car to explain what’s next: “Measurements and data analysis will continue, since physicists still need to find out in the months and years to come what the wheels are like: everything standard (i.e. as expected) or extra-large rims or something even more unexpected (perhaps on fire?).”
Just because the Standard Model appears to be validated, doesn’t mean there isn’t a lot more to discover in the field of particle physics, too, as Schoonderwoerd explains: “The standard model doesn’t explain gravitation at all. So physicists have been trying to unify the gravitation theory with the Standard Model in advance models with names like Supersymmetry.” He says that many of the people investigating these theories hope that accelerators like the Large Hadron Collider will continue to run at increasing energy levels, uncovering new particles that may explain how gravity works in a way that fits into the Standard Model.