B^0-bar
The term "B^0-bar" refers to the antiparticle of the neutral B meson, denoted as B^0. B mesons are subatomic particles made up of a bottom quark and a light quark, such as an up or down quark. The "bar" indicates that it is the antiparticle, which means it contains the corresponding antiquarks.
B^0-bar plays a significant role in particle physics, particularly in the study of CP violation, which helps explain the matter-antimatter asymmetry in the universe. Experiments involving B^0-bar and its decays contribute to our understanding of fundamental forces and the behavior of particles at high energies.