"I think we have it" said the Director General of CERN, Rolf-Dieter Heuer on 4th July. He was referring to 'The God particle'. The term for the Higgs boson coined by the physicist Leon Lederman (noble laureate) in his 1993 popular science book, "The God Particle: If the Universe Is the Answer, What Is the Question? The elusive nature of the particle has baffled the scientists for over 45 years but finally it was found. Its discovery has created a great excitement not only among the scientists but among the common masses and religious scholars as well because this strange particle is giving mass to the universe and its ability to explain why the universe is the way it is. It is as if we have found the key to solve the mysteries of the universe that has been puzzling us for thousands of years.
The theories and discoveries of physicists over the past century have resulted in a remarkable insight into the fundamental structure of matter. The discovery of 'The God particle' is regarded as a major breakthrough in the field of particle physics. Though Peter Higgs, an atheist reportedly finds 'the God Particle' terminology offensive because it shifts our focus from science to religion, he was overwhelmed by the announcement of the discovery. Finding 'the God Particle' is a great scientific discovery and a landmark day in physics but at the same time it is just one stop in the long journey in which Physics still has a long way to go.
Going back to the history of the atom, John Dalton (1766-1844) introduced the idea of atom for the first time when he developed the first useful atomic theory of matter famously called Dalton's atomic theory which states that atoms are the fundamental building blocks of matter.
In 1898, the J. J. Thompson discovered the first component part of the atom, the electron, a particle with negative electric charge. In 1911 Rutherford discovered that the atom has a concentrated positive nucleus and in 1913 Neil Bohr moved ahead with Rutherford's model of the atom to include that electrons are orbiting the nucleus in discrete radii. Rutherford's discovery of the nucleus demonstrated that these positive charges were concentrated in a very small fraction of the atoms volume and it led the discovery of proton in 1919 and its credit goes to Rutherford. After that In1932 James Chadwick announced the discovery of neutron. Therefore during 1930s the structure of the atom was realized such that, that atom has a central nucleus made of neutrons and protons and electrons were circling around it in discrete regions.
The things did not stop here. In 1963 Murray Gell-mann came up with the idea of quarks, the ultimate entities from which neutrons, protons (called hadrons) are composed of. Though these quarks have not been observed directly but the theoretical predictions based on their existence have been confirmed experimentally.
Today we have reached a stage where we say that everything around us and in the universe is found to be made from twelve basic building blocks called fundamental particles. These fundamental particles are grouped into quarks and leptons (lighter particles class) and are governed by four fundamental forces of the universe. This has been encapsulated in a mathematical Model know by the name standard model which was developed through a combination of theory and experiment over a period of time. Though the gravity is not consistent with the theory, the model is predictive guide for describing the known fundamental particles and their interactions. It has successfully explained a host of experimental results and precisely predicted a wide variety of phenomena and has become an established and well-tested physics theory.
The 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. These particles did not have any mass at that time. As the universe cooled and the temperature fell below a critical value, an invisible force field which became commonly know as the 'Higgs field' was formed together with the associated particle, now called the 'Higgs boson' postulated in 1964 by Peter Higgs. The Higgs field was thought to be a theoretical and invisible energy field that pervades the whole cosmos. It is through their interaction with the Higgs field that particles gained mass and eventually formed the universe. The more the particle interacts, the heavier they become, whereas particles that never interact are left with no mass at all. Some particles, like the photons that make up light, are not affected by it and therefore have no mass.
The Grand Unified Theory is a vision of physicists to combine all the four fundamental forces viz. the strong force, the weak force, the electromagnetic force and the gravitational force into one single formula to explain the whole universe. The first step toward the unification of these forces was achieved when the weak and electromagnetic interactions were unified under electroweak theory by Prof Abdul Salam and others who were awarded the Nobel Prize for this in 1979. The confirmation of the theory was established in two stages first in 1973 and latter in 1983. The discovery of the three massive W+, W¬ and Z particles called vector bosons, in 1983 was hailed as a confirmation of the theories.
In order for this theoretical unification of electroweak theory to make a mathematical sense, all three particles have to be massless which was not true according to experiments. And only if these particles could obtain a mass by interacting with a background field – the Higgs field – will the underlying unified theory explain why the two forces appear different at the scales we measure them today, while remaining mathematically consistent. Thus this special type of coupling to a particle could make the weak interaction bosons able to become massive without destroying the symmetries.
For nearly 30 years since the discovery of the W+,W¬ and Z particles, experimental physicists have been trying to build particle accelerators with the energy necessary to recreate a very small model of the state of the universe as it was in the first trillionth of a second after the Big Bang, to produce a Higgs field. First in Fermi Lab's at Tevatron particle Collider near Chicago and later in a similar machine at CERN, the European Organization for Nuclear Research, the search was on. Now the search for the Higgs boson is over as the two teams hunting for it in proton-proton collision at Large Hadron Collider, the most powerful particle accelerator at CERN have now independently confirmed, that they have found the subatomic particle.
The Higgs boson was the last missing piece of the Standard Model, the theory that describes all the particles, forces and interactions that make up the universe. The discovery is just the end of the beginning and confirming the existence of the Higgs boson would be the start of a new era of physics. More is unknown than is known. The "God particle" could possibly unlock some of the universe's great mysteries which include dark matter, dark energy, unification of all the forces, besides testing countless theories in physics.
The author is Associate Professor & Head Dept of Physics, Amar Singh College, Srinagar. Feedback at (Emails: email@example.com)