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A meson with total angular momentum one and negative parity. In the ordinary quark model, a quark-antiquark pair with orbital angular momentum zero and total spin one has these quantum numbers; its neutral self-conjugate states have charge conjugation $C=-1$. The light-flavour tensor product gives an octet and a singlet, forming a vector nonet, just as spin-zero negative-parity pairs form a pseudoscalar meson nonet. Nonzero orbital excitations can also produce vector states.

A theory violates charge conjugation when conjugating particles to antiparticles changes a physical interaction or its transition probabilities. This is different from CP violation: an interaction can violate charge conjugation and parity symmetry in quantum field theory separately while preserving their combination.