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Particles Tell Stories

For Newton, it was apples. For Einstein, it was trains and Swiss clocks. Today, physicists use particles to discover new laws of nature in the microscopic world. The discovery of a new particle is often the opening chapter of an entirely new story revealing unsuspected features of the universe.

When the positron, the brother of the electron, was first detected, the discovery went beyond the identification of a particle. The positron revealed a hidden half of the universe: the world of antimatter. The positron showed how to reconcile the laws of relativity with the laws of quantum mechanics. The positron told a brand-new story about the structure of space and time.

When physicists first observed the pion in cosmic ray detectors atop the Pyrénées, they were puzzled. Soon, particle accelerators began producing myriad cousins of the pion: etas, deltas, rhos, omegas. Physicists were running out of Greek letters to name them all. Finally the story became clear. These were not elementary particles at all, but tiny bags of quarks, held together by a new force, a force so strong that no quark could ever escape it.

Other aspects of the universe may also unveil themselves in the form of new particles – extra dimensions of space, for example. An electron moving in tiny extra dimensions would not look like an electron to us; it would appear as a much heavier new particle, “heavier” because it is whirling around the extra dimensions. In fact, the tiny extra dimensions imply whole “towers” of new heavy particles. Producing some of these particles with an accelerator would be a great discovery; an equal challenge will be to pin down their identities as travelers in extra dimensions. How much we learn from these particles depends on how well we determine their properties. For example, by measuring their masses, physicists could discover the shape of the extra dimensions.

Using the LHC and a linear collider, physicists hope to produce particles of dark matter in the laboratory. They may well discover an entire dark world, with other new particles that tell a brand-new story of the dark and the visible universe.