In the late 1960's, the Standard Model (SM) of physics was developed to study elementary particles and forces of nature. It is a menagerie of 17 structureless fundamental particles (6 of them quarks), which are the basic building block of the universe. Quarks exist inside particles called hadrons - composites of either three quarks or a quark-antiquark pair bound together by gluons.
Despite the success of the SM in explaining sub-nuclear physics, it cannot explain how the particles acquire masses. In order to understand the origin of masses, a hypothetical, ubiquitous quantum field was introduced into the model by the Scottish physicist Peter Higgs. Hence, it is called the Higgs field and the particle associated with the field is called the Higgs boson. It is a zero-spin electrically neutral particle. The Higgs boson is sometimes referred to as “God” particle after Nobel physicist Leon Lederman described it as a “goddamn particle.” As the last remaining particle out of 17 particles of the SM that has not been observed, Higgs has become the “most sought after particle in modern physics.”
How does the Higgs boson give mass to the particles? According to the SM, the Higgs field forms the basic underlying structure of the universe and it permeates throughout the cosmos. When a massless particle passes through the Higgs field, it gains mass by interacting with the field, i.e. the particle will cause the field to cluster around it. The more clustering there is, the more mass the particle will accumulate. It will give quarks and gluons their large masses, but little or no mass to the neutrinos and photons.
Experimental hunt to find the Higgs boson is being carried out at the Large Hadron Collider (LHC) at CERN, Geneva. Experiments were also performed at the Tevatron at Fermi Lab near Chicago until its closure last year. The biggest obstacle to finding the Higgs is that before the search began, no one knew exactly in what energy range to look for it. In order to detect it, theorists determined that conditions that existed in the universe nanoseconds after the Big Bang have to be simulated in the lab. This can be achieved by making high energy (greater than 1 trillion electron volt) proton beams crash into each other, hoping that the Higgs will appear “fleetingly in the wreckage.” The LHC is the first accelerator capable of reaching such high energy. But even with the LHC, the journey has not been easy and the search still continues.
If Higgs boson is detected, it would put the half-century old Standard Model and all its predictions on a secure foundation. It would also help to unify two of the fundamental forces of the universe the electromagnetic force that governs interactions between charged particles and the weak nuclear force that's responsible for radioactive decay. The unification will be a step closer towards the Grand Unified Theory of all the forces Einstein dreamed of. It will also open the door to a whole new world of super particles, “overweight twins” of the existing particles, predicted by Supersymmetry an extension of the Standard Model. This will eventually allow us to have a better understanding of cosmology and the origin of dark matter, extra dimensions of String Theory and black holes.
If the Higgs boson is not discovered, it will possibly lead to more subtle and exotic theories, like the Technicolor theory, to explain what gives particles mass. It could also mean that quarks are not fundamental particles, but made up of some more complex but smaller particles.
Whether the “god” particle is detected or not, there is no denial that we are at the threshold of a momentous event, an event that will determine the future course of direction of physics. According to the leader of one of CERN's two experiments scheduled for this year, “we're close to getting something in focus. We know we're close to the stage where we're going to see something."
Quamrul Haider, PhD, is professor and Chairman, Dept of Physics and Engineering Physics, Fordham University, New York.
e-mail: haider@fordham.edu
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