Why does matter have mass? In other words, what decides how heavy a particle is? Why are some matter particles heavier than others? These are some of the fundamental questions answered by the concept of a Higgs Field pervading all space and its quantum or mediating particle, the Higgs Boson.
Till date, the idea of such a field was entirely conjecture, but today it is closer to reality with the actual discovery of a Higgs-like particle, which may indeed be the real deal. One of the primary goals behind building the LHC (Large Hadron Collider - The most powerful particle smashing machine ever created) at CERN was the detection of this boson.
At the time of writing, the two teams working on ATLAS and CMS experiments at CERN have announced the detection of a boson at an energy scale of 125.3 ± 0.6 GeV (Giga electron volt - A measure of energy), which fits the Higgs particle profile, but confirmation can only be provided after further investigation.
To explain why this discovery of a new fundamental building block of the universe is as momentous as man's landing on the Moon or the discovery of nuclear fission, let me explain the whole idea in the simplest possible way.
The Party Analogy - A Simple Explanation For the Higgs-Curious Layman
Now imagine a popular movie star walking into the party venue. Guests throng around him, making it difficult for our star to move around freely. He is slowed down by the 'field' of guests surrounding him.
Now picture a particle, like an electron, entering the Higgs field and being thronged by bosons in a similar way. That's how every particle is slowed down by interaction with the Higgs field, endowing it with apparent mass, in the process. It's analogous to a swimmer being slowed down by molasses in a pool he is swimming through.
Depending on how well the Higgs field sticks to a particle, it gains mass in that proportion. With this discovery, we now understand how the stuff that we are made of, gains mass. If it wasn't for the Higgs field, the fabric of matter which weaves the material world wouldn't exist. The 'God Particle' reference however, has no religious relations whatsoever.
About Fermions, Bosons and the Higgs Hunt
Particle physics has discovered the entirety of all stuff in the visible universe to be made up of just 12 particles. They include six quarks (up, down, top, bottom, strange, charmed) and six leptons (electron, electron neutrino, muon, muon neutrino, tau, tau neutrino).
There is an additional set of antiparticles (particles with same mass but opposite charge), which are mysteriously low in number in the universe. Protons and neutrons, the particles which make all the atomic nuclei in the universe are made up of up and down quarks.
Along with electrons they make bonding between atoms possible, making the creation of beautifully complex structures possible. All these 12 particles that constitute the fabric of the material world are known as fermions (After the great physicist Enrico Fermi). The property that distinguishes them is their inability to clump together too closely.
Quarks and Leptons are the building blocks of the universe. They are bound together by the four fundamental forces of nature - Gravitation, Strong, Weak and Electromagnetic force to create the beautiful complexity of the world around us. These forces, excluding gravity, are now known to be mediated by the latter set of particles, which are bosons.
Named after the Indian Physicist Satyendra Nath Bose, who collaborated with Albert Einstein to develop the statistics that govern these particles, bosons can clump together closely in great numbers. Photons mediate the electromagnetic force between particles, gluons mediate the strong force between quarks, and the weak force is mediated by W and Z bosons.
Bosons are quantum excitations of their corresponding fields. When the associated field gets excited, a boson is created. The Higgs boson is also the quantum excitation of a Higgs field, which permeates spacetime. It was hypothesized by a bunch of scientists including Peter Higgs in 1964, to solve a particularly vexing problem in theoretical physics.
For the established theory related to the electromagnetic and weak forces to work, the particles involved had to be massless, but in actuality they had mass. Ergo, the Higgs mechanism and the Higgs Field was proposed to create a method by which the mathematics came out right and the theory stayed consistent with its underlying framework.
As the lowest state excitation of this field, the Higgs Boson followed as a theoretical consequence. So in a way, the theory demanded that there be a Higgs field and a boson associated with it!
Subsequently, the Higgs mechanism was used successfully to unify the electromagnetic and weak forces, making it a cornerstone of the Standard Model of particle physics, which describes the entire hierarchy of particles and forces that make our world.
Therefore, finding the Higgs Boson naturally became the single most important piece of evidence, the Holy Grail, which would validate the standard model. However, finding it proved to be a tough job, because it was known to be massive, with no precise mass value predicted.
Just like the periodic table of atomic elements hinted towards an underlying structure of protons, neutrons, and electrons, physicists are curious about what kind of structure makes the basis of the quark-gluon periodic table of elements. That was another motivation for the Higgs hunt, which has now succeeded in finding the mass endowing particle.
How Does the Higgs Boson Endow Mass to Particles?
Matter particles swim through a Higgs Field which pervades all space and depending on how they interact with this field, they acquire mass.
Particles which experience more resistance or drag, while traversing through this field, appear to have more mass. There are some particles like photons, which do not interact with the field at all. That may be the reason why photons have no mass. The particle associated with this field, which supposedly endows mass to other particles, is the Higgs Boson.
According to this model, in the absence of such a boson, all particles would be massless and would simply zoom past each other into space at the speed of light, making binding of particles and their clumping due to gravity impossible, thereby wiping out the chances of life emergence in the future.
The universe as we know it, wouldn't exist if there was no Higgs-like field endowing mass to particles. Einstein's special theory of relativity showed us that energy and matter are inter-convertible.
The Large Hadron Collider is a phenomenal particle smashing machine, which accelerates two proton beams close to the speed of light and makes them collide to create pure energy, from which a host of particles get generated.
Among this plethora of particles, created for minute fractions of a second, scientists have now found a Higgs-like particle, whose precise nature will be revealed in the coming few months. This event has altered our understanding of the universe forever.
As we delve deeper into the mysteries of spacetime and matter, we develop an even greater respect for the beautiful complexity of our world, stretching from quarks, Higgs bosons to human minds, who question the working of it all.