Time for a little history lesson.

Wind the clock back to the late 1960s and early 1970s.

At this time, physicists were trying to make sense of some of the "zoo" of particles they were discovering in particle accelerators. One of the methods for making sense of that "zoo" of particles, was to postulate that the electromagnetic force and weak nuclear force were, at suitable energies, unified into a single electroweak force.

Performing this unification of the two forces, required physicists to postulate the existence of three new particles - the two W bosons, one positively charged, the other negatively charged, and the electrically neutral Z boson.

At this point, it's apposite to digress for a moment, and inform you about what a "boson" is.

Subatomic particles possess a quantity known as "spin", which is a measure of intrinsic angular momentum, as opposed to angular momentum acquired as a result of orbiting something else. The connection with classical angular momentum of large rotating bodies is, however, incomplete (you expect anything to be straightforward in quantum mechanics?). As might be expected, the value of spin for a particle is quantised - it's only allowed to take certain discrete values, instead of lying within a continuum. Thanks to a fortuitous historical accident, particles like electrons and protons came to have spins that took values of the form (n+½), where n is an integer, while other particles (e.g., photons of light) came to have spins that took whole integer values (n).

Electrons and other matter particles are fermions - they have half-integer spins of the form (n+½), and obey the Pauli Exclusion Principle.

Particles that are involved with the transmission of forces, on the other hand, are bosons, and they have integer spins.

It turns out that the spin value of a boson, courtesy of that happy accident where fermions were assigned half-integer spins, fortuitously tells us a lot about the type of force a boson is associated with. A boson with spin 0 is a scalar boson, and is associated with scalar quantities like mass. A boson with spin 1 is a vector boson, and is associated with vector quantities, such as velocity, force, momentum etc. It so happens that the Standard Model of particle physics allows for the existence of spin 2 bosons, and these are associated with exotic quantities best represented by mathematical entities known as "rank 2 tensors". Indeed, a scalar quantity is a rank 0 tensor, and a vector quantity is a rank 1 tensor, so rank 2 tensors are, in effect, like vectors but "even more so". The exact details are the cornerstone of some fairly intimidating pure mathematics classes at undergraduate level, which I'll spare you, despite having endured them myself! But, for future reference, note that gravity is postulated in the quantum world to need a spin 2 boson. Which is one of the reasons why gravity is a bitch to integrate with the other forces. But, I digress.

So, having covered what a boson is, back to that 1970s exercise in unifying the electromagnetic and weak nuclear forces.

To do so, physicists required that the W and Z bosons were vector bosons, like photons - i.e., had a spin value of 1. So, the hunt was on for unusual spin 1 particles that had not been seen before, one with a positive electrical charge, one with a negative electrical charge, and one electrically neutral. Upon finding those, the physicists at the time would know that their work had been pretty much correct.

Well, the W and Z bosons were duly found. And, duly found to be spin 1 bosons with the requisite charges.

Just one teeny fly in the ointment at this point.

The theory of electroweak unification predicted that these particles would be massless. This was already a somewhat controversial development, because massless bosons would mean that the weak nuclear force extended over an infinite range, and thus far, its interactions were observed to be confined to small subatomic distances. For the forces to be restricted, the particles needed to possess mass, and fairly substantial mass at that.

When the particle accelerator data was in, what did the physicists find?

They found that the W and Z bosons possessed hefty masses. Masses easily sufficient to restrict the range of action of the weak nuclear force to small distances.

At this point, there was a problem. How to account for those observed masses in the theory.

Say hello to Peter Higgs, who, along with others, devised a mechanism. Namely, the introduction of a new quantum field (subsequently named the Higgs field), and an associated boson, the Higgs Boson. Which was required, since it was a determinant of mass, to be a scalar boson with spin 0.

Thus began a forty year hunt for it.

The Higgs Boson turned out to be an elusive little beast, and persuading a free Higgs Boson to appear in a particle accelerator experiment, so that it could be detected, turned out to be, well, seriously bloody hard. While that search was on, alternative resolutions of the W and Z mass problem were devised, just in case the Higgs Boson turned out to be elusive enough not to exist, as it were.

Then, CERN stepped up to the plate, with a brand new and very powerful accelerator. To give you an idea how powerful, the Large Hadron Collider, when in operation, uses as much electrical power in one day as my house does in forty three years. The construction bill for this behemoth was around $10 billion, and the electricity bill for its operation is around $8 million per year. That's one seriously expensive piece of kit. It's also unusual in another respect. Most physics labs house the equipment within their walls, whereas in the case of CERN, the lab is a building sitting on top of the apparatus, which occupies a circular tunnel 27 miles in diameter.

Well, this massive machine was duly fired up, and ...

... after a LOT of experimental runs, data turned up consistent with the appearance, although very briefly, of a free Higgs Boson. Furthermore, its measured properties, for the time being, slot pretty neatly into the theory that was produced 40 years previously.

Now at this point, if you're wondering why this mass-donating particle doesn't donate mass to photons, well, that takes us into the territory of hardcore quantum operator theory, and again, this isn't for the faint hearted. But apparently, it's responsible for donating mass to just about everything apart from photons and neutrinos. Any particle with a decent mass owes that mass, in no small part, to the Higgs Boson, though in the case of quarks, things are more complicated still, courtesy of confinement and the action of gluons. You should now be in a position to understand why it takes 15 years of hard study to become a properly accredited particle physicist.

Enjoy.