The Higgs Boson Discovery
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This is the first in a series of five posts by Pearson Science on one of the greatest scientific breakthroughs of the year.
1. Higgs Boson Discovery | 2. Collaboration and Competition | 3. Teaching the Higgs Boson | 4. Hands-On Activity: Colliding Particles | 5. Hands-On Activity: What’s in the Box?
Have you ever stopped and wondered why your body’s particles don’t blast off at the speed of light?
Probably not, but maybe you should, because until this summer, scientists had yet to demonstrate why the particles with mass don’t blast into the cosmos at the fastest speed possible. Your particles owe their slowness—their mass—to something called the Higgs field, which was only recently confirmed to exist.
Mass is so familiar that it’s easy to take for granted – from bowling balls to protons, it’s tough to imagine anything without it. Nevertheless, massless particles do exist: specifically, photons, which are responsible for the light you’re using to read this article. Photons travel at the speed of light (3 x 108 m/s), which is exactly how fast your particles would be traveling if they, like photons, lacked mass. Put another way, mass slows matter down. If mass suddenly ceased to exist, everything, including you, would explode forth at light speed.
But if mass anchors matter to the fabric of the universe, what exactly is it attaching to? Could there really be some kind of invisible, nearly undetectable field permeating everything, even the vacuum of space?
Even before this summer’s announcement, there were reasons for scientists to believe that such a field did exist.
First of all, fields make particles of matter do the things they do. The electromagnetic field, for instance, causes electrons to be attracted to protons. If there’s a field for electrical charge, why not mass?
Secondly, the existence of the Higgs field is essential to the workings of modern physics. Over the course of the last century, physicists have put together a unifying theory of almost everything, which is known as the Standard Model. It accounts for every known force and field, except gravity and the mysterious phenomenon known as dark energy. But for the Standard Model to make sense, it requires the existence of a field responsible for mass.
A group of scientists predicted this field in the 1960s, but this hypothesis would take close to 50 years to confirm because the field itself is undetectable. Luckily, every field comes with its own particle, and the Higgs field was no exception. (The particle, the Higgs boson, as well as the Higgs field, bear the name of Peter Higgs, who predicted the particle’s existence in 1964.) The Higgs boson would prove essential to confirming the existence of the Higgs field.
In a 1964 paper, Peter Higgs, now 83, theorized about the existence and role of an unknown boson, which was later named after him. Here he stands near the CMS detector, which was used to observe the Higgs boson. (Credit: CERN)
But first, why do particles and fields come in pairs? The answer is that particles are made of fields, in the same way that a wave in the ocean is made of water.
The photon is the particle, or point of excitation, that corresponds to the electromagnetic field. Even though a photon acts in some ways like a discrete object floating through space like a hockey puck, it’s also a wave traveling through the electromagnetic field, which permeates the entire universe.
Scientists knew that for the Higgs field to exist, it would also have to have a corresponding particle—the Higgs’ version of what the photon is to the electromagnetic field. But this particle, known as the Higgs boson, would be unstable and thus couldn’t be found in nature—as soon as it came into existence, it would disintegrate into smaller particles.
Since the particle couldn’t be found, scientists would have to create it. In theory, the plan sounds complicated: blast high-energy particles together until they produce a Higgs boson, which could only be detected as a result of the particles produced when it decays. In practice, it’s even harder. First, the amount of energy necessary to smash these particles together was huge, only obtainable in the largest particle accelerators in the world, such as the Large Hadron Collider, a massive particle accelerator on the border between France and Switzerland. To make matters worse, scientists didn’t know how much energy it would take to create the particle, so they had to blast particles together using a wide range of different energy levels. And finally, the decay products of the Higgs boson were the same decay products of other particles, meaning that it would be difficult to tell if a Higgs boson, and not a more mundane particle, had been created during each collision.
The experiments took decades before teams at the Large Hadron Collider finally announced they had found a winner (and were reasonably certain it was the Higgs, or at least one example of a Higgs boson). The particle forms at 125 gigaelectron volts (a unit of energy), they discovered.
This yellow circle marks the Large Hadron Collider. Labels mark locations of specific research facilities, such as ATLAS and CMS, whose teams discovered the Higgs boson earlier this year. (Credit: CERN)
Now that we know the Higgs field exists, so what? Most essentially, the subatomic particles in your body can interact with the Higgs field, similar to the way electrons interact with the electromagnetic field, and have mass. It’s important to note that Higgs bosons are not found in atoms, and aren’t directly responsible for your body’s mass. Rather, other subatomic particles composing your body’s protons and neutrons interact with the Higgs field and take on mass themselves.
But the discovery only raises more questions. We still don’t know why different particles take on different amounts of mass. We don’t know how gravity comes into play. We don’t even know if the Higgs is really only one field, or if it’s composed of several fields. But scientists are working hard to find out. And the potential for future discoveries is huge.
A little over a hundred years ago, when scientists first described the electron, electricity wasn’t of much use to anybody at the time, but over the years electricity has permeated almost every aspect of our lives. This year, the Higgs field and its corresponding particle were discovered. It’s difficult to imagine how this discovery will affect our lives in the future. But in the meantime, it’s good to know that you’re not about to explode into a cloud of particles traveling at the speed of light.
The following “comic book” about the Higgs boson does an excellent job of making these concepts more tangible and conveying the enthusiasm that inspires particle physicists to explore a realm that is largely unseen.
The Higgs Boson Explained from PHD Comics on Vimeo.
