Footprints, shadows and reality

Over the last four-five years the world of fundamental physics has been revolving around the concept of the so-called Higgs Boson (HB hereafter), a particle whose media-favourite name is “God’s particle”. To look for this particle, CERN (European Organisation for Nuclear Research) in Geneva, the most advanced laboratory in the world for experiments with very high energy particles, has been desperately carrying out particle collisions.

It is expected that when fundamental particles are made to collide at very high energies they may break and transform into something new. That way one may hope to find new particles and new interactions. Two large teams of scientists hoped to discover the presence of HB in this way. And finally, they seem to have evidence that the HB took part in the aftermath of these collisions. Before taking a look at the experiment itself, let us see why the scientists are so desperate to establish the existence of HB and why it has been given the grandiose title of “God’s particle”.
The history of physics shows that in their attempt to understand the mysteries of nature, physicists like to work in terms of laws of nature. The laws may be many and diverse to begin with, but the ideal situation towards which scientists set their path of progress is one with fewer laws with wider applicability. Take, for example, the Coulomb law of electrical attraction which talks about how electrical charges attract or repel each other. There is a similar law about magnetic attraction and repulsion. These apparently different-looking laws were brought under one umbrella for unification by James Clerk Maxwell with the notion of the electromagnetic field. That was in 1865; more than a century later further unification occurred between the electromagnetic force and another force of nature called the “weak force”. The so-called electro-weak force is the result of the investigation by physicists Abdus Salam and Steven Weinberg. The path of progress now seems to point towards the strong force: can it be brought under the same fold of unification? And, ironically, apparently the last milestone on this route to unification is the force of gravitation, the first force of nature to be formally discovered. This was the discovery by Isaac Newton, allegedly inspired by the falling apple.
There is a rule of the thumb that helps guide the scientist going along the path of unification. Just as the chemist made progress probing matter at smaller and smaller scale, down to the atomic and molecular structure, the physicist proceeds further down the scale looking at sub-atomic and sub-nuclear particles. However, to probe at smaller and smaller scales one needs larger and larger energy for the probing particles. The unification of electricity with magnetism did not require very high energy particles. But the next step did. The verification of the electro-weak force demanded particle collisions at energies around a hundred times the energy of the proton, which is the main component particle in the nucleus of an atom.
As one works towards understanding the basic properties of matter, one is faced with the question: “Where and how does a particle acquire the property of mass?” If one may trace the dawn of modern physics to the three laws of motion proposed by Isaac Newton, then one realises that the above question will claim to have remained unanswered for the longest duration. For, what Newton tells us is that everybody in this universe has the property of inertia. When we try to move a chunk of matter lying at rest, we have to apply force. It is easier to move a football than a canon ball of the same size. These differences reflect that inertia is not the same for all bodies. Newton’s laws tell us that the quantitative measure of inertia is mass. But we still do not know how mass originates, nor do we know what determines the mass of a body.
In a modern theory of subatomic particles this question remains unanswered. However, the ideas proposed by Peter Higgs in the early 1960s assumed that a particle, which later came to be called the Higgs particle, is responsible for assigning masses to other particles. The standard model of particle physics, which has been taken as a starting point for any modern theory of fundamental particles, requires the Higgs particle to exist and prescribes the expected range of its mass and some of its basic properties. For example, all fundamental particles are classified as bosons or fermions, depending on whether their distribution follows the rules laid down by Indian physicist Satyen Bose or Italian physicist Enrico Fermi. The Higgs particle is a boson and hence called the Higgs Boson. Over the years it has acquired the name of “God’s particle”, so referred to by Nobel laureate Leon Lederman because of its fundamental nature. However, many scientists do not like this title which unnecessarily brings God into the picture.
So the discovery of the HB with mass in the expected range will make the standard model of particle physics that much more credible. If it is not found or found with quite a different mass, then a lot of ideas in modern particle physics may have to be revised. Cosmologists, who study the issue of origin of the universe, are also interested spectators on the sidelines, for they have their own list of questions starting with how matter was formed and distributed after the universe supposedly originated in a Big Bang.
It is in this context that we have to look at the important discovery announced by CERN on Wednesday, July 4, 2012. The analysis of observed collision events indicates that a particle which behaves as a boson and with a mass considerably larger than the mass of a typical subatomic particle like the proton or a neutron has been found. It is consistent with the expected properties of the HB but, as the scientists associated with the discovery are at pains to point out, it is too early to conclude that it is the HB they are looking for. One needs patience and more analysis before drawing that conclusion.
In this context I came across an analogy: you are looking for somebody you know on a beach and you see footsteps that match his and you also hear the report of a shadow seen that matches your friend. Thus you are confident that he is somewhere on the beach, but you have not yet seen him in flesh and blood.
The Higgs Boson is like that fleeting shadow.