Finally I have come back to this topic. In my last post on the same topic I could not talk either about the Higgs boson or about the results that CERN released in December 2011, in detail. I hope to explain the two in this post.
Higgs boson is a theoretical particle (at least till now), proposed by Peter Higgs, that forms an integral part of the Standard Model of Particle Physics. The standard model is the most comprehensive theory yet, describing Electromagnetic, strong nuclear and weak nuclear forces. The reason why the Higgs boson forms an important part of the standard model is that it explains why some particles have mass, like electrons and quarks, while others are massless, like photons and gluons.
So how does the Higgs boson give mass to other subatomic particles? The standard model predicts the existence of a field called the Higgs field which permeates the Universe. The way a particle interacts with this field describes how massive it is. In quantum mechanics, the quanta of a field is a boson (force carriers). That is, a particle can interact with a field by exchanging bosons. For example, to interact with an electromagnetic field one exchanges photons (a boson) with the field. In the case of the strong nuclear force, the boson is called a gluon. Similarly for the Higgs field, it is the Higgs boson.
So how does the Higgs boson give mass to other subatomic particles? The standard model predicts the existence of a field called the Higgs field which permeates the Universe. The way a particle interacts with this field describes how massive it is. In quantum mechanics, the quanta of a field is a boson (force carriers). That is, a particle can interact with a field by exchanging bosons. For example, to interact with an electromagnetic field one exchanges photons (a boson) with the field. In the case of the strong nuclear force, the boson is called a gluon. Similarly for the Higgs field, it is the Higgs boson.
A simple analogy is often used to describe the Higgs field. Let us consider a film awards ceremony with photographers and interviewers (media persons) waiting in a hall for the actors to arrive. If a lesser known actor arrives, he can cut across the hall without being noticed by the media persons. Hence he can cross the hall quickly. But when the lead actors arrive, every photographer wants to click a photograph and every interviewer wants to interview them. Therefore it takes a very long time for them to cross the hall. Here the photons and gluons are similar to the lesser known actors. They don't interact with the Higgs field (media persons) and they travel at the speed of light. Particles like electrons and quarks are similar to the lead actors. They interact more with the media persons and hence travel slowly. This is a very good analogy to understand the basics of the Higgs field.
The Higgs field was incorporated into the standard model in 1967 by Abdus Salam and Steven Weinberg. Incorporation of the Higgs field not only explained why particles have masses but it also substantiates an equally important phenomenon in quantum mechanics called spontaneous symmetry breaking. I am not going to go into the details of symmetry breaking as it is a tough phenomenon to explain here. But what I want to stress here is that the Higgs field is an integral component of the standard model and detecting the Higgs boson is crucial to validating the standard model.
Theorists calculated that the Higgs boson weighs about 140 times (120-130 GeV) the mass of a proton. To detect such heavy particles, experimentalists require really powerful particle accelerators. The construction of one such accelerator began in Geneva, Switzerland in the mid-90s - the Large Hadron Collider (LHC). I won't be talking about the LHC in this post. I hope to write another post about it very soon.
The LHC has been operational for about two years now and it has been scanning the energy spectrum in search of the Higgs boson. CERN released its first set of results in August 2011 which was not very encouraging but another set of results that was released in December 2011 excited the physics community. Both ATLAS and CMS, two of the largest detectors at the LHC, detected particles in the 124-126 GeV energy range that could be the Higgs boson. This is an exciting news but it does not prove that the Higgs boson exists because results from the two detectors give 2.6 (CMS) and 3.6 (ATLAS) sigma significance, which is good in most experiments. But in particle physics a particle said to be detected only when the results give 5 sigma significance. To get such a result the LHC has to acquire more data which it would be able to do by the end of 2012.
So what happens if the LHC doesn't find the Higgs boson in the 124-126 GeV energy range? Theorists say that there is a possibility that the Higgs boson can have a mass of about 600 GeV, an energy level that LHC hasn't explored yet. But it is generally accepted that the Higgs boson cannot be that massive. So what happens if the LHC does not find the Higgs boson at all? Many physicists say that this would be exciting because it would give them an opportunity finally disprove Peter Higgs' 50 year old theory and then come up with a new theory to explain the mass of particles. But if the LHC finds the Higgs boson, it would not only substantiate the predictions of the standard model but would also celebrate the power of mathematics in describing the physical world around us.
Higgs or no Higgs, 2012 promises to be an exciting year for physics.
The LHC has been operational for about two years now and it has been scanning the energy spectrum in search of the Higgs boson. CERN released its first set of results in August 2011 which was not very encouraging but another set of results that was released in December 2011 excited the physics community. Both ATLAS and CMS, two of the largest detectors at the LHC, detected particles in the 124-126 GeV energy range that could be the Higgs boson. This is an exciting news but it does not prove that the Higgs boson exists because results from the two detectors give 2.6 (CMS) and 3.6 (ATLAS) sigma significance, which is good in most experiments. But in particle physics a particle said to be detected only when the results give 5 sigma significance. To get such a result the LHC has to acquire more data which it would be able to do by the end of 2012.
So what happens if the LHC doesn't find the Higgs boson in the 124-126 GeV energy range? Theorists say that there is a possibility that the Higgs boson can have a mass of about 600 GeV, an energy level that LHC hasn't explored yet. But it is generally accepted that the Higgs boson cannot be that massive. So what happens if the LHC does not find the Higgs boson at all? Many physicists say that this would be exciting because it would give them an opportunity finally disprove Peter Higgs' 50 year old theory and then come up with a new theory to explain the mass of particles. But if the LHC finds the Higgs boson, it would not only substantiate the predictions of the standard model but would also celebrate the power of mathematics in describing the physical world around us.
Higgs or no Higgs, 2012 promises to be an exciting year for physics.
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