D^- is a type of subatomic particle known as a meson. Specifically, it is a combination of a charm quark and an anti-down quark. Mesons are important in the study of particle physics because they mediate the strong force that holds atomic nuclei together. D^- particles are produced in high-energy collisions, such as those occurring in particle accelerators like the Large Hadron Collider. They have a relatively short lifespan, decaying into other particles almost immediately after their creation. Studying D^- and similar particles helps scientists understand the fundamental forces and interactions in the universe.