Essay: 2nd Award 2004: Probing Gravitational Interactions of Elementary Particles

The gravitational interactions of elementary particles are suppressed by the Planck scale M _* ~ 10¹⁸ GeV and are typically expected to be far too be weak to be probed by experiments. We show that, contrary to conventional wisdom, such interactions may be studied by particle experiments in the next few years. As an example, we consider conventional supergravity with a stable gravitino as the lightest supersymmetric particle. The next-lightest supersymmetric particle (NLSP) decays to the gravitino through gravitational interactions after about a year. This lifetime can be measured by stopping NLSPs at colliders and observing their decays. Such studies will yield a measurement of Newton's gravitational constant on unprecedentedly small scales, shed light on dark matter, and provide a window on the early universe.