Wednesday, July 18, 2012

Universe: Higgs Boson & CERN

CMS Higgs-event.jpg
The Higgs boson is named for Peter Higgs who, along with two other teams, proposed the mechanism that suggested such a particle in 1964[6]and was the only one to explicitly predict the massive particle and identify some of its theoretical properties. In mainstream media it is often referred to as "the God particle", after the title of Leon Lederman's book on the topic (1993). Although the proposed particle is both important and elusive, the epithet is strongly disliked by physicists, who regard it as inappropriate sensationalism since the particle has nothing to do with God nor any mystical associations,and because the term is misleading: the crucial focus of study is to learn how the symmetry breaking mechanism takes place in nature - the search for the boson is part of, and a key step towards, this goal.
The Higgs boson or Higgs particle is a proposed elementary particle in the Standard Model of particle physics. The Higgs boson's existence would have profound importance in particle physics because it would prove the existence of the hypothetical Higgs field - the simplest of several proposed explanations for the origin of the symmetry-breaking mechanism by which elementary particles gain mass.The leading explanation is that these particles acquire mass by interacting with the Higgs field, which has non-zero strength everywhere, even in otherwise empty space. If this theory is true, a matching boson—the smallest possible excitation of the Higgs field—should also exist and be detectable, providing a crucial test of the theory. Consequently, it has been the target of a long search in particle physics. One of the primary goals of the Large Hadron Collider (LHC) at CERN in Geneva, Switzerland—the most powerful particle accelerator and one of the most complicated scientific instruments ever built—is to test the existence of the Higgs boson and measure its properties which would allow physicists to confirm this cornerstone of modern theory.
According to the Standard Model, the Higgs particle is a boson, a type of particle that allows multiple identical particles to exist in the same place in the same quantum state. It has no spin, electric charge, or colour charge. It is also very unstable, decaying into other particles almost immediately. If the Higgs boson were shown not to exist, other "Higgsless" models would be considered. In some extensions of the Standard Model there can be multiple Higgs bosons.
Proof of the Higgs field (by confirming its boson), and evidence of its properties, are seen as likely to greatly affect human understanding of the universe, validate the final unconfirmed part of the Standard Model as essentially correct, indicate which of several current particle physics theories are more likely correct, and open up "new" physics beyond current theories.
On 4 July 2012, the CMS and the ATLAS experimental teams at the LHC independently announced that they each confirmed the formal discovery of a previously unknown boson of mass between 125–127 GeV/c2, whose behaviour so far was "consistent with" a Higgs boson, while adding a cautious note that further data and analysis were needed before positively identifying the new particle as being a Higgs boson of some type.

We have a Higgs Boson snapshot, not complete picture:
Why should ordinary people care at all?
Even before particle physicists, people have asked the question - what is everything made up of? How we all are made up of? It’s not enough to just say that electrons and nucleus make an atom, we should also be able to say why they are sticking together and not breaking apart.

Finding the Higgs Boson in some sense is the last bit of that answer of how things are put together. It’s the final piece of puzzle in the bricks and mortars of nature. This was one piece that was missing from our understanding of the building blocks of nature.
Physicists have already discovered many fundamental Bosons and Fermions. What they hadn’t discovered till now was the Spin Zero Boson, which we had predicted existed. This is something we had understood about the Standard Model. Actually right now we have not proved that the particle is Spin Zero. Right now all we have are indications that there is a Boson. What is the spin of this Boson is something we don’t know, but we know that it is not a Spin One Boson. So, we are beginning to think that we may have our guy.

Until now we only had footprints of the Higgs Boson and no proof. Now we have a snapshot of the particle, but it is still hazy. There is a lot more work that needs to be done.  If the Higgs Boson particle had not been found, we would be back to the drawing board so to speak. We would have had to have revised our notions and begin afresh.

Beyond standard model
Before we could think about physics beyond the Standard Model, we had to find the last piece of the Standard Model. Now we are trying to see if there are small differences in the Higgs Boson particle. In fact we are hoping for this, because the failure of the Higgs Boson to be exactly as it was predicted will end up giving us directions and implications of physics beyond standard model.
We don’t know if there is only one Higgs Boson. We don’t know yet. There are theories that there could be more Higgs Bosons and some theories predict that the Higgs Boson’s properties would be different. Now our job is to see if this is the Higgs Boson described by the Standard Model.

The make-up of the Universe
This is where one needs to appreciate the strength of the Standard Model of particle physics. An experiment that someone does in a lab at the distance scale of an atom or nuclei actually tells us how energy is generated in Sun. Probing the laws of nature at a distance scale of 1 Fermi is actually like studying something at one millionth of a centimetre. The laws of physics that are operating inside a nucleus that are studied in a lab are found to be true at cosmological distances as well.

The misconceptions
I wish people would stop calling it the God’s Particle. It’s a very important particle and thousands of particle physicists have been searching for it and it’s a particle whose existence proves that the humanity’s understanding of the basic laws was correct. So, in a sense this should concern all of humanity. But it has nothing to do with it being God’s Particle.

Being at CERN
It was absolutely fantastic. I have been going to CERN a lot in the last few years to teach at the summer school or for workshops and conferences and interacted quite a bit with experimental physicists as well. I reached CERN on June 14 and there were already rumours that something big was going to happen. We would speculate in the cafeteria about what it could be and when the announcement would take place. On the day of the announcement, my lecture series was supposed to begin in the morning, but was pushed off to the afternoon for obvious reasons. The atmosphere was just electric.

Published: Wednesday, Jul 18, 2012, By Aishhwariya Subramanian: Bangalore
Prof Rohini Godbole of the Centre for High Energy Physics, Indian Institute of Science, the discovery of the Higgs Boson particle was special as she was present at CERN European Laboratory for Particle Physics in Geneva, delivering a series of lectures at its summer school. One of the top scientists in the field as well as a frequent visitor to CERN, Godbole elaborates what Higgs Boson really means and why it had generated excitement in the cafeterias of CERN.