Discovery Scenarios

Dark Matter in the Laboratory

Like the jelly beans in this jar, the universe is mostly dark: 95 percent consists of dark matter and dark energy. Only about five percent (the same proportion as the colored jelly beans) of the universe – including the stars, planets and us – is made of familiar atomic matter.
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Four percent of the universe is familiar matter; 23 percent is dark matter, and the rest is dark energy. Although the amount of dark matter in the universe is now well known, its identity is a complete mystery.

Physicists have proposed many exotically named dark matter candidates: neutralinos, axions, gravitinos, Q balls, and WIMPzillas. For simplicity, most theoretical studies assume that all of dark matter is composed of a single kind of new particle. But if the dark universe is as rich and varied as the visible world, this assumption may someday appear as simplistic as ancient theories of earth, air, fire and water.

A major goal of the LHC and ILC is to identify one or more components of dark matter by producing particles of dark matter in the laboratory and studying their properties. Astrophysical evidence suggests that dark matter particles will show up at the Terascale. The current understanding of particle physics and cosmology allows physicists to extrapolate back to early times in the history of the universe. Assuming that dark matter particles are weakly interacting relics of the Big Bang, physicists can use the observed dark matter density to estimate the particles’ mass. Detailed calculations in many different theoretical frameworks show that the mass of the dark matter particles place them at the Terascale.

Physicists working at the LHC are likely to find the first evidence for Terascale dark matter. But is it really dark matter? Is it all of the dark matter? Why is it there? A linear collider would provide the ideal environment to answer these questions, making precise measurements of the dark matter particles and their interactions with other particles. Linear collider exper iments could establish both the what and the why for this chapter of the dark matter story.