(*) They were proposed in the Peccei-Quinn theory, and in certain string interactions predicted by quantum chromodynamics, these psuedo-Goldstone bosons may explain the lack of violation of CP-symmetry, which is known as the strong-CP problem.
They couple to both quarks and leptons according to the Dine-Fischler-Srednicki-Zhitnitsky model, which is a competitor of the Kim-Shifman-Vainshtein-Zakharov model.  A namesake solar telescope at CERN has been used to search for them as a result of their supposed production in stellar interiors via the Primakoff effect. (*) They were proposed in the Peccei-Quinn theory, and in certain string interactions predicted by quantum chromodynamics, these psuedo-Goldstone bosons may explain the lack of violation of CP-symmetry, which is known as the strong-CP problem. For 10 points, name these hypothetical light, pseudoscalar particles and dark matter candidates.
They couple to both quarks and leptons according to the Dine-Fischler-Srednicki-Zhitnitsky model, which is a competitor of the Kim-Shifman-Vainshtein-Zakharov model.  
{axions}