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Higgs Boson : The God Particle

 

 

"for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles, and which recently was confirmed through the discovery of the predicted fundamental particle, by the ATLAS and CMS experiments at CERN's Large Hadron Collider"

Finally, François Englert and Peter W. Higgs are jointly awarded the Nobel Prize in Physics 2013 for the theory of how particles acquire mass. In 1964, they proposed the theory independently of each other (Englert together with his now deceased colleague Robert Brout). In 2012, their ideas were confirmed by the discovery of a so called Higgs particle at the CERN laboratory outside Geneva in Switzerland.

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The awarded mechanism is a central part of the Standard Model of particle physics that describes how the world is constructed. According to the Standard Model, everything, from flowers and people to stars and planets, consists of just a few building blocks: matter particles. These particles are governed by forces mediated by force particles that make sure everything works as it should.

The entire Standard Model also rests on the existence of a special kind of particle: the Higgs particle. It is connected to an invisible field that fills up all space. Even when our universe seems empty, this field is there. Had it not been there, electrons and quarks would be massless just like photons, the light particles. And like photons they would, just as Einstein’s theory predicts, rush through space at the speed of light, without any possibility to get caught in atoms or molecules. Nothing of what we know, not even we, would exist.

Both François Englert and Peter Higgs were young scientists when they, in 1964, independently of each other put forward a theory that rescued the Standard Model from collapse. Almost half a century later, on Wednesday 4 July 2012, they were both in the audience at the European Laboratory for Particle Physics, CERN, outside Geneva, when the discovery of a Higgs particle that finally confirmed the theory was announced to the world.

CERN announced on 4 July 2012 that they had experimentally established the existence of a Higgs-like boson, but further work is needed to analyse its properties and see if it has the properties expected from the Standard Model Higgs boson. On 14 March 2013, the newly discovered particle was tentatively confirmed to be + parity and zero spin, two fundamental criteria of a Higgs boson, making it the first known fundamental scalar particle to be discovered in nature. The Higgs mechanism is generally accepted as an important ingredient in the Standard Model of particle physics, without which certain particles would have no mass.

The explanation offered by physics is that space is filled with many invisible fields. The gravitational field, the electromagnetic field, the quark field and all the other fields fill space, or rather, the four dimensional space-time, an abstract space where the theory plays out. The Standard Model is a quantum field theory in which fields and particles are the essential building blocks of the universe.

In quantum physics, everything is seen as a collection of vibrations in quantum fields. These vibrations are carried through the field in small packages, quanta, which appear to us as particles. Two kinds of fields exist: matter fields with matter particles, and force fields with force particles — the mediators of forces. The Higgs particle, too, is a vibration of its field — often referred to as the Higgs field.

Without this field the Standard Model would collapse like a house of cards, because quantum field theory brings infinities that have to be reined in and symmetries that cannot be seen. It was not until François Englert with Robert Brout, and Peter Higgs, and later on several others, showed that the Higgs field can break the symmetry of the Standard Model without destroying the theory that the model got accepted.

This is because the Standard Model would only work if particles did not have mass. As for the electromagnetic force, with its massless photons as mediators, there was no problem. The weak force, however, is mediated by three massive particles; two electrically charged W particles and one Z particle. They did not sit well with the light-footed photon. How could the electroweak force, which unifies electromagnetic and weak forces, come about? The Standard Model was threatened. This is where Englert, Brout and Higgs entered the stage with the ingenious mechanism for particles to acquire mass that managed to rescue the Standard Model.

The Higgs field is not like other fields in physics. All other fields vary in strength and become zero at their lowest energy level. Not the Higgs field. Even if space were to be emptied completely, it would still be filled by a ghost-like field that refuses to shut down: the Higgs field. We do not notice it; the Higgs field is like air to us, like water to fish. But without it we would not exist, because particles acquire mass only in contact with the Higgs field. Particles that do not pay attention to the Higgs field do not acquire mass, those that interact weakly become light, and those that interact intensely become heavy. For example, electrons, which acquire mass from the field, play a crucial role in the creation and holding together of atoms and molecules. If the Higgs field suddenly disappeared, all matter would collapse as the suddenly massless electrons dispersed at the speed of light.

So what makes the Higgs field so special? It breaks the intrinsic symmetry of the world.

Our universe was probably born symmetrical. At the time of the Big Bang, all particles were massless and all forces were united in a single primordial force. This original order does not exist anymore — its symmetry has been hidden from us. Something happened just 10^(-11) seconds after the Big Bang. The Higgs field lost its original equilibrium. How did that happen?
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It all began symmetrically. This state can be described as the position of a ball in the middle of a round bowl, in its lowest energy state. With a push the ball starts rolling, but after a while it returns down to the lowest point.

However, if a hump arises at the centre of the bowl, which now looks more like a Mexican hat, the position at the middle will still be symmetrical but has also become unstable. The ball rolls downhill in any direction. The hat is still symmetrical, but once the ball has rolled down, its position away from the centre hides the symmetry. In a similar manner the Higgs field broke its symmetry and found a stable energy level in vacuum away from the symmetrical zero position. This spontaneous symmetry breaking is also referred to as the Higgs field’s phase transition.

The renowned physicist Prof Stephen Hawking added his praise: "In the early 60s, theorists were struggling to understand why particles have mass. Peter Higgs and Francois Englert proposed a mechanism called symmetry breaking. This mechanism also predicted a massive particle, the Higgs boson. The discovery last year at Cern of a particle with the correct properties confirms this prediction and is a triumph for theory."

 

 


Source: Nobel Prize official website and some other random online/offline sources.


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