The Particle at the End of the Universe: How the Hunt for the Higgs Boson Leads Us to the Edge of a New World Read Free Page A

Democritus’s sense of indivisible building blocks of matter. Today we call them “elementary particles.” Two kinds of quarks—known playfully as “up” and “down”—go into making the protons and neutrons of an atomic nucleus. So, all told, we need only three elementary particles to make up every single piece of matter that we immediately perceive in the environment around us—electrons, up quarks, and down quarks. That’s an improvement over the five elements of antiquity, and a big improvement over the periodic table.
    Boiling the world down to just three particles is a bit of an exaggeration, however. While electrons and up and down quarks are enough to account for cars and rivers and puppies, they aren’t the only particles we’ve discovered. There are actually twelve different kinds of matter particles: six quarks that interact strongly and get confined inside larger collections like protons and neutrons, and six “leptons” that can travel individually through space. We also have force-carrying particles that hold them together in the different combinations we see. Without force particles, the world would be a boring place indeed—individual particles would just move on straight lines through space, never interacting with one another. It’s a fairly small set of ingredients to explain everything we see around us, but frankly, it could be simpler. Modern particle physicists are driven by a desire to do better.
    The Higgs boson
    That’s the Standard Model of particle physics: twelve matter particles, plus a group of force-carrying particles to hold them all together. Not the tidiest picture in the world, but it fits all the data. We have assembled all the pieces needed to successfully describe the world around us, at least here on earth. Out in space we find evidence for things like dark matter and dark energy, stubborn reminders that we certainly don’t understand everything yet—these are most certainly not explained by the Standard Model.
    For the most part the Standard Model divides nicely into matter particles and force-carrying particles. The Higgs boson is different. Named after Peter Higgs, who was one of several people who proposed the idea back in the 1960s, the Higgs boson is somewhat of an ugly duckling. Technically speaking it’s a force-carrying particle, but it’s a different kind of force carrier from the ones we’re most familiar with. From the viewpoint of a theoretical physicist the Higgs seems like an arbitrary and whimsical addition to an otherwise beautiful structure. If it weren’t for the Higgs boson, the Standard Model would be the epitome of elegance and virtue; as it is, it’s a bit of a mess. And finding the mess-maker has proven to be quite a challenge.
    So why were so many physicists convinced that the Higgs boson must exist? You’ll hear explanations like “to give mass to other particles” and “to break symmetries,” both of which are true but not easy to absorb at first glance. The main point is that without the Higgs boson, the Standard Model would look very different, and not at all like the real world. With the Higgs boson, it’s a perfect match.
    Theoretical physicists certainly tried their best to come up with theories that didn’t have a Higgs boson, or one in which the boson was quite different from the standard story. Many of the theories failed when confronted with the data, and others seemed unnecessarily complicated. None looked like a true upgrade.
    And now we’ve found it. Or something very much like it. Depending on how careful physicists are being, they will say either, “We’ve discovered the Higgs boson,” or “We’ve discovered a Higgs-like particle,” or even “we’ve discovered a particle that resembles the Higgs.” The July 4 announcement described a particle that behaves very much like the Higgs is supposed to behave—it decays into certain other particles in more or less the ways we expect it to. But it’s still early,