Anti-quarks do not typically reside in the nucleus of atoms as part of ordinary matter. Quarks and anti-quarks are elementary particles that make up protons and neutrons, which are the building blocks of atomic nuclei. However, in normal matter, only quarks are found within the protons and neutrons.
Anti-quarks are the antiparticles of quarks, carrying opposite electric charge and other quantum numbers. They can be created in laboratory experiments through high-energy particle collisions or in specific particle interactions. These processes generate anti-quarks along with their corresponding quarks.
In certain extreme conditions, such as high-energy particle accelerators or cosmic-ray interactions, quarks and anti-quarks can briefly exist as free particles outside of protons and neutrons. However, they quickly combine with other quarks or anti-quarks to form mesons or baryons due to the strong force, which binds quarks together.
In summary, anti-quarks can be created in laboratory experiments or occur naturally in high-energy interactions, but they are not typically found as constituents of atomic nuclei in ordinary matter.