July 16, 2012

What does the discovery of Higgs boson mean?


Arvind Gupta

July 9, 2012
On 4 July 2012, the Geneva based European Organisation of Nuclear Research (CERN) announced the discovery of the Higgs Boson particle. The CERN press release said, “We observe in our data clear signs of a new particle, at the level of 5 sigma, in the mass region around 126 GeV.” The press release was, however, cautious: “The results presented today are labelled preliminary. They are based on data collected in 2011 and 2012, with the 2012 data still under analysis... A more complete picture of today’s observations will emerge later this year after the LHC provides the experiments with more data…” Thus, while the possibility that it may be a more exotic particle than the Higgs particle has not been ruled out, the confidence that the newly discovered particle is indeed the elusive Higgs particle is within an error tolerance of one in a million.

The discovery of the elusive particle will be rated as one of the greatest discoveries. The particle had been eluding scientists since its existence was predicted in 1964 by Peter Higgs, a British physicist, and five other scientists independently. It cost $10 billion to build the Large Hadron Collider, particle accelerator, at the CERN lab in Geneva. The LHC experiment involved colliding opposite beams of protons at energy levels of 4 TeV per nucleon. The LHC can generate energies up to 7 TeV. One terraelectronvolt is 1,000,000,000,000 eV. (On a lighter note, someone has calculated that the LHC, running at full energy levels, will be operating with about the same amount of energy that seven flying mosquitoes have in kinetic energy. But remember this much energy is supplied to each proton. That is a huge kick for the particle.)

The Higgs Boson has a mass of about 125 GeV. Electron volt or eV is the unit of energy used to measure the mass of elementary particles. One GeV is one billion electron volts. The Higgs particle has no charge and it disintegrates within a tiny fraction of a second after its birth. It leaves behind particles that can be detected. The Higgs particle was observed in proton-proton collisions at the Large Hadron Collider at extremely high energies.

With the discovery of the Higgs boson, the missing link in the Standard Model of physics has been found. The Standard Model had predicted a number of fundamental particles like quarks and leptons which have already been found. The discovery of the Higgs particle will strengthen the Standard Model further.

The Standard Model is a quantum mechanical theory that has been evoked to peer into the structure of matter. Being one of the most successful theories in physics, its validation through the discovery of the Higgs particle is a big relief for scientists. Had Higgs not been found, the very basis of particle physics would have been challenged.

One of the problems that had been nagging scientists was how the fundamental particles acquire mass. In order to explain the existence of mass, scientists had postulated what in particle physics parlance is called the Higgs mechanism. In simplified terms, it means that the universe is permeated by a field called the Higgs field. Elementary particles acquire mass when they interact with this field. Without the Higgs field, the particles would move at the speed of light and have no mass. No mass would mean no structure in the universe. Thus, to explain the structure of matter, the Higgs field was postulated. The field is associated with a particle which is called the Higgs Boson. That particle has now been found.

The Standard Model can be understood in another way. There are four fundamental forces in nature that give rise to matter and its structure. These are: the familiar electro-magnetic force; the weak force; the strong force which operates within the atom’s nucleus; and gravity, which keeps the planets and galaxies in the universe moving. Each force is associated with a particle or a set of particles. The electromagnetic force is associated with electrons and the weak and strong forces are associated with a host of other fundamental particles. The Higgs particle is associated with the strong force.

Scientists have been looking to find one single unified force to unify the four fundamental forces. They have, however, succeeded in unifying the three forces, the electromagnetic, the weak and the strong forces through the Standard Model. The Higgs particle provides the evidence that the unification of the three forces is correct. However, the force of gravity has resisted any attempt at unification with the other three forces.

The discovery of the Higgs particle notwithstanding, physics still has to grapple with a number of puzzles. Why is there prevalence of matter over anti-matter in the universe? Why is there so little mass in the universe—only four per cent of what ought to be there. Where is the missing 96 per cent? The mystery of missing matter, also dubbed as Dark Matter, has yet to be explained. Physics is replete with speculative theories like the ‘theory of everything’, ‘string theory’ of extra dimensions and so on. The discovery of Higgs boson may throw some light on these fundamental questions.

Particle physics and the Standard Model are too complicated to be understood by laymen. Yet, the public has been glued to the Higgs Boson and the Large Hadron Collider for several years now. There were speculations that the high energy collision experiment in the 27 km long tunnel of the LHC would create black holes that would gobble up the planet earth. The name ‘God particle’ for Higgs boson also caught media attention.

What about the Indian connection to Higgs Boson? Is there one? India, an observer member of CERN, has been involved in the building of some components of the LHC. It will be a stretch to claim a direct Indian connection to the discovery of the Higgs Boson. But the discovery of the particle has certainly thrown a spotlight on the much neglected Indian physicist Satyendra Nath Bose, a contemporary of Albert Einstein. In quantum mechanics, the Bose-Einstein statistics is a critical tool used to understand the behaviour of a category of particles known as Bosons.

Along with the Higgs Boson, the world is rediscovering S. N. Bose. The Higgs particle, like many others, is a Boson, and also the heaviest Boson discovered so far. There are several of them, for instance, the Z-boson and the W-boson. Z-boson was discovered in the nineties in high energy collisions. But S.N. Bose, who died in 1974, was not directly connected with the formulation of the Standard Model.

Pakistan has a more direct connection to the recent discovery. Noble laureate Abdus Salam, a Pakistani scientist, had contributed in a significant way to the development of the Standard Model. He formulated the electroweak theory, which unifies the electromagnetic forces with weak forces at the sub-atomic level. He also suggested how to incorporate the Higgs mechanism into the Standard Model. It is unfortunate that the great scientist was humiliated in Pakistan because he was an Ahmediya. He had collaborated with an Indian origin scientist Jogesh Pati in developing the Pati-Salam model in 1974, which throws light on the unification of quarks and leptons. Jogesh Pati is an Orissa born professor emeritus at the University of Maryland.

Truth is elusive and has many shades. One can approach it but never actually find it. There will always be more to be done. Scientists will now get busy in investigating the characteristics of the newly found particle. The discovery of Higgs boson renews the faith in the scientific method. A theory must be supported by evidence. Here is a lesson for researchers who are trying to uncover truth in their respective fields.

The discovery of the Higgs boson represents the triumph of big science which requires big money. Some people may argue whether spending such large sums is justified when billions of people in the world go hungry every day. The history of science has shown that spending on intellectual enquiry is as important as spending on basic necessities. It is worthwhile to remember that the ‘world wide web’, which has made stupendous contribution to the growth of the internet, originated at CERN. The techniques used to analyse the massive raw data collected by the sensors from billions of collisions will be useful in other spheres too. The chances are that there will be spin offs from the experience gained in building and operating the LHC.

The author is Director General, IDSA. The views expressed are his personal.

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