What Is the Higgs Boson and Higgs Field?

To make sense of the Higgs boson, it is necessary to begin with the Higgs field. This field endows certain fundamental particles with mass and distinguishes two of nature’s four fundamental forces from one another.

The possibility of such a field was first proposed in the early 1960s. Physicists explored what a theoretical field might mean for the separation of electromagnetism and the weak force, as well as for the fact that some force-carrying, or gauge, particles have mass – including W and Z bosons – whereas others, such as photons, do not.

British physicist Peter Higgs was among several scientists developing this model. His name subsequently became associated with the field, its particle and the process through which it works.

So, what is the Higgs boson?

Like every quantum field, the Higgs field produces a corresponding type of fundamental particle: the Higgs boson. It is a comparatively heavy, electrically neutral and extremely unstable boson – a force-carrying particle with zero spin – which survives only briefly before decaying into one of several possible combinations of other particles.

In 2012, two detectors at the Large Hadron Collider identified a particle of precisely this kind. Its discovery formally established the Higgs boson within the Standard Model and offered compelling evidence for the Higgs mechanism.

What makes particles massive?

In daily life, mass is felt as resistance to motion. Objects with substantial mass are difficult to set moving and, once moving, difficult to bring to a halt.

Albert Einstein’s theory of special relativity offers a further perspective: mass is a manifestation of an object’s energy.

While at rest, an object’s mass equals its energy divided by the speed of light squared – a variation on the well-known equation E=mc2. Put an object in motion, particularly close to light speed, and it acquires energy that behaves as mass.

Atoms derive most of their mass from the energetic activity of quarks moving within their nuclei, where the strong force binds them together.

However, quarks possess mass even in isolation, as do the electrons around them. Since there is nothing 'buzzing' within these particles, another form of activity must explain the energy equivalent to their mass at rest.

Furthermore, physicists in the mid-20th century found that earlier descriptions of gauge bosons did not fit the evidence. Short-range particles, such as the W and Z bosons of the weak force, were 80 times more massive than an entire proton, while the photon of the long-range electromagnetic field had no mass whatsoever.

Physicists urgently needed an explanation for this disparity in mass and for the sharp distinction between the two fields.

How does the Higgs field give fundamental particles mass?

During the extraordinarily hot moments immediately after the Big Bang, the electromagnetic and weak nuclear force fields would have been almost indistinguishable.

As the Universe expanded and cooled, those fields would have separated. One would operate through heavy bosons across the tiny distances within a nucleus, while the other would use bosons light enough to extend over immense distances through space.

Several teams of physicists worldwide developed similar accounts of this division and the differing masses involved. History credits the 1964 proposal by Higgs and his colleagues François Englert and Robert Brout, which centred on a new type of quantum field active everywhere, including apparently empty space.

A field with a non-zero value throughout every part of the Universe would disrupt a basic quantum-mechanical balance. In theory, this ought to create a type of particle that experiments had already excluded.

Higgs, Englert and Brout, however, demonstrated that connecting this hypothetical field to the weak-force field would allow the unseen, problematic particle to be absorbed. What remained would be heavyweight W and Z bosons, alongside a relatively heavy, spinless and uncharged 'Higgs' boson that would rapidly break apart.

Picture the Higgs field as a sweet shop, where bosons are slow to hurry because they are busy eating chocolate, leaving a scattering of short-lived 'Higgs wrappers' behind them.

It quickly emerged that essentially the same mechanism could apply to almost any quantum field. The Higgs field accounts for the masses of numerous other fundamental particles, including quarks and electrons, all of which resist being pushed as they pause to satisfy their sweet tooth.

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