B^- refers to the negatively charged version of the B meson, a type of subatomic particle made up of a bottom quark and an anti-up quark. It is part of the family of particles known as mesons, which are composed of a quark and an antiquark. B^- mesons are important in the study of particle physics and help scientists understand the behavior of matter and antimatter. The B^- meson can decay into various other particles through weak interactions, which are one of the four fundamental forces in nature. Studying these decays provides insights into the Standard Model of particle physics and the properties of flavor physics, which examines how different types of quarks transform into one another.