Free The Particle at the End of the Universe: How the Hunt for the Higgs Boson Leads Us to the Edge of a New World by Sean Carroll

intently was a modest volume entitled High Energy Physics , by Hal Hellman. I was doing my reading in the late 1970s, but the book had been written in 1968, before the Standard Model was put together—back when quarks were exotic and somewhat scary-sounding theoretical speculations. But hadrons had been discovered in abundance, and High Energy Physics was full of evocative photographs of particle tracks, each representing a fleeting glimpse of nature’s secrets.
    Many of these photographs had been taken at the mighty Bevatron, one of the leading particle accelerators of the 1950s and ’60s. The Bevatron was located in Berkeley, California, but that’s not where the name came from; it was derived from “billions of electron volts,” the energy the accelerator was able to reach. (As we’ll explain below, an electron volt is a weird unit of energy much beloved by particle physicists.) One billion corresponds to the prefix “giga–,” so a billion electron volts is one GeV, but back in those days Americans would often use “BeV,” and besides, “Gevatron” just doesn’t sound right.
    The Bevatron contributed to two Nobel Prizes: in 1959 to Emilio Segrè and Owen Chamberlain, for the discovery of the antiproton, and in 1968 to Luis Alvarez, for the discovery of too many particles to count—all those pesky hadrons. Sometime later, Alvarez and his son Walter were the ones who first demonstrated that an asteroid impact was the likely cause of the extinction of dinosaurs, by discovering an anomalously high concentration of iridium in geological strata that formed around that time.
    The idea behind particle accelerators is simple: Take some particles, accelerate them to very high velocities, and slam them into some other particles, watching carefully to see what comes out. The procedure has been compared to smashing together two fine Swiss watches and trying to figure out what they are made of by watching the pieces fly apart. Unfortunately, this analogy has it backward. When we smash particles together, we’re not looking for what they are made of; we’re trying to create brand-new particles that weren’t there before we did the smashing. It’s like smashing together two Timex watches and hoping that the pieces assemble themselves into a Rolex.
    To attain these velocities, accelerators use a basic principle: Charged particles (such as electrons and protons) can be pushed around by electric and magnetic fields. In practice, we use electric fields to accelerate particles to ever-higher speeds, and magnetic fields to keep them moving in the right direction, such as around the circular tubes of the Bevatron or the LHC. By delicately tuning these fields to push and nudge particles in just the right way, physicists can reproduce conditions that would otherwise never be seen here on earth. (Cosmic rays from outer space can be even more energetic, but they are also rare and hard to observe.)

The influence of a magnetic field on moving particles. If the magnetic field is pointing upward, it pushes positively charged particles in a counterclockwise direction, negatively charged particles in a clockwise direction, and neutral particles not at all. Likewise, stationary particles just remain at rest.
    The technological challenge is clear: Accelerate particles to as high an energy as we can, smash them together, and look to see what new particles are created. None of these steps is easy. The LHC represents the culmination of decades of work learning how to build bigger and better accelerators.
    E = mc 2
    When the Bevatron created antiprotons, it wasn’t because there were antiprotons hidden in the protons and atomic nuclei they were working with. Rather, the collisions brought new particles into existence. In the language of quantum field theory, the waves representing the original particles set up new vibrations in the antiproton field, which we detect as particles.
    In order for that to happen, the crucial ingredient is that