Axion

In theoretical physics, an axion is a hypothetical elementary particle implicitly introduced by the Peccei–Quinn theory in 1977 to resolve the strong CP problem in quantum chromodynamics (QCD). In 1978 Frank Wilczek and Steven Weinberg independently published papers explaining how the Peccei-Weinberg theory implies named the existence of a new hypothetical particle. Wilczek named the new particle the "axion" after Colgate-Palmolive's Axion (brand) brand of laundry detergent, because the new particle cleaned up the strong CP problem. Quotes ... In my view, after more than 25 years, the preferred solution to the strong CP problem still remains the idea that the Standard Model has an additional U(1)PQ symmetry. Such a solution, necessarily, predicts the existence of a concomitant axion. Roberto Peccei, The Strong CP Problem and Axions by Roberto Peccei https://books.google.com/books?id=XdyibnUFagYC&pg=PA15 Axions: Theory, Cosmology, and Experimental Searches 9783540735175 7 December 2007 Springer 3–17 ; quote from p. 15 (edited by Markus Kuster, Georg Raffelt, and Berta Beltrán) … Remember that quark masses arise in the Standard Model because the Higgs field has a non-zero vacuum value. Roberto and I saw that one could add an additional symmetry to the theory in such a way that it is automatic that the vacuum energy is minimized for θeffective = 0. Technically this new global U(1) symmetry is not quite an exact symmetry. Like the strong CP symmetry itself, it is a pseudo-symmetry, broken only by non-perturbative or instanton (tunneling) effects. …The additional pseudo-symmetry has a consequence, as was pointed out by Weinberg … and Wilczek … namely that there is an additional pseudo-Goldstone boson, now known as the axion, associated with it. The fact that Roberto and I did not notice this obvious phenomenological consequence of our model shows that we were focused on the general solution to the strong CP problem. I, at least, was so happy to find a general solution to that that I did not stop to examine other phe- nomenological implications of the model we built to demonstrate the idea before we published it. But the axion implication is common to all such models, for it arises from the symmetry itself. Helen Quinn, hep-ph/0110050 The CP Puzzle in the Strong Interactions 2001 2001hep.ph...10050Q (quote from pages 7 & 8) It is pointed out that a global U(1) symmetry, that has been introduced in order to preserve the parity and time-reversal invariance of strong interactions despite the effects of instantons, would lead to a neutral pseudoscalar boson, the "axion," with mass roughly of order 100 keV to 1 MeV. Steven Weinberg, 10.1103/PhysRevLett.40.223 A New Light Boson? 1978 Physical Review Letters 40 4 223–226 1978PhRvL..40..223W External links axion Category:Quantum mechanics