By now, the dust has settled around the discovery of the Higgs boson, and no doubt the Higgs mechanism is at work generating the mass. The public was excited on July 4, 2012 with the announcement of the discovery of the Higgs boson. Now they want to know, “What’s next?”
Rolf Heuer, the director general of Cern, came recently to our rather unusual conference in Calcutta, “Frontiers of Science,” carrying the message of this landmark discovery. At the public lecture he delivered at the Centenary Hall of Calcutta University, there must have been at least 1500 young students listening to Heuer in rapt attention. Both of us were ‘mobbed’ afterwards, more so Heuer, obviously. He said in his own way, “This kind of experience is only reserved for rock stars.” I have also felt, time and again, that this kind of euphoria among the youth in Calcutta is just fantastic — only possible in Calcutta; young persons, not all of them from the science stream, just went crazy; they simply wanted to share the excitement. This is a particularly wonderful experience since neither of us is a rock star or a film star, not even a football player and certainly not a political star.
Let me now explain a few basic points about the Higgs boson, which I hope will help readers to understand why Higgs at all, why Higgs is so important. At the centre of the puzzle lies the answer to the very old but fundamental question — how is the mass of any elementary particle generated? A person has a certain amount of mass — and because of gravity he gains weight, and by eating beyond his limit he gains further weight.
Mass comes from all the ingredients of the body, bones, flesh, blood and so on. These ingredients are essentially made of molecules, the DNA of the gene is a molecule. Molecules are made of atoms, at the centre of which lies the atomic nucleus, surrounded by circling electrons. To present an analogue to the size of things: if the atom is like a standard football field, a pea in that field is the nucleus, its size is one-millionth of a millionth of one centimetre. The nucleus is made of neutrons, protons and mesons. Mesons, rather like the shuttlecock in a badminton game, are the messengers between protons and neutrons, one proton to another proton, one neutron to another neutron, strongly binding them together.
The neutrons and the protons are made of quarks and gluons, the gluons binding the quarks together. So, the ultimate question of a body’s mass and its origin boils down to the mass of quarks and gluons. We know these very elementary objects have mass.
But, how is the mass generated? How do quarks acquire mass?
The answer is that the mass is generated by the Higgs mechanism — the Higgs boson interacting with itself generates the mass.
Let us go back to the British science minister, William Waldegrave, in 1993; he threw a challenge to everybody to explain in the simplest terms in the form of a cartoon (oh dear) on an A4 paper the same question, “What was the Higgs and why was it so important?” Britain was hard pressed to contribute 55 million pounds per year to Cern. So Waldegrave had the bright idea around 1993 of explaining to the public and to the legislators the famous Higgs boson in the form of a cartoon. By the way, Waldegrave’s heroine was Margaret Thatcher, who had just left the office of the prime minister. John Major had taken over.
So the cartoon has two components, and David Miller of University College, London was the winner. The prize was a bottle of vintage champagne Brut 1943. It went something like this: “Imagine a roomful of MPs assembled in a room [sic], agitating for the arrival of a very important person. All of a sudden, the door opens and a lady comes in, none other than the former prime minister, Margaret Thatcher. The MPs forget about their point of agitation but cluster around her, gather around her. Thatcher’s progress is impeded, she has to slow down as if she has become heavier.”
Thatcher, as it were, was the particle. By interacting with the members of parliament representing the Higgs field, she gained mass. The cartoon had flaws, but by now is the centrepiece for the Higgs mechanism all over the world. So, Thatcher gained mass by the Higgs mechanism just as a human body gains mass by the same mechanism. This is why the Higgs boson is so godd***ed important.
On July 4, the world woke up with the discovery of a boson whose mass is close to the theoretical prediction. A lot more has to be done to identify it exactly, only the mass has been discovered so far.
The Higgs boson or Higgs field has far-reaching consequences. Alan Guth, working at the Massachusetts Institute of Technology in 1981, suddenly stumbled on to the idea that almost immediately after the Big Bang, the universe expanded exponentially, that is usually known as cosmic inflation. There are many models of inflation in the market, but everybody agrees that the energy driving the inflation is due to a field very much like the Higgs field, rather similar to the original idea of Peter Higgs in 1964.
But the more profound question is to do with dark matter which makes up about a quarter of the mass of the universe. We know that from experimental evidence, verified many times over by now. The visible universe, that is, what we can see, consists of only a few per cent of the total mass of the universe.
This dark world still remains a mystery. Made up of dark particles we still don’t know, it refuses to interact with our visible world, rather like the invisible agents protecting Thatcher. Then what stops dark stars, dark planets even dark life forms from existing; indeed, some argue, the entire dark world may be much simpler than our world, so the complex ‘visible world’ can’t see it.
The Higgs boson may well be the best chance we have ever had to have a feel of the dark world. It is straightforward to assert that the Higgs field will be in some way connected to a different but again, in some sense similar, Higgs field that gives mass to the dark particles of the dark universe. This link is quite likely to be the correct picture and it thus gives us a chance to have our looking glass to the dark world and speculate and eventually discover what the dark particles could be.
Two crucial features of the Higgs boson make it interesting. One, it looks the same from every direction. The second feature is that the Higgs field of the Higgs boson is spread over all space. Thus the Higgs field is extraordinarily sensitive to the tiniest fluctuations in energy; that tiny fluctuation can ripple through, tunnelling from the dark world to our world; indeed that ripple can give us a clue to the dark world.
It is not surprising that all of us who made some contribution to the understanding of the Big Bang through the Alice detector at the Large Hadron Collider and to the discovery of the Higgs boson at the Atlas and CMS are so excited. We may well be on the verge of discovering the dark universe, just as the same way our explorers of yesteryear discovered the various continents.