DEMON and high energy theory

A study is carried out to examine several appealing gauge models to accomodate CP violation. There are two sources of DEMON (dipole electric moment of neutron): so-called theta vacuum of QCD, and CP violating weak interaction. The presence of the first source is rather suprising since it is usually considered that the strong interaction, which is well described by QCD, conserves T and CP exactly. Investigation is made of these issues. Another investigation is made of DEMON due to Weak CP violation. It is found that the models examined predict quite different values of the coupling constant (DEMON). In particular, the most popular standard model by Kobayashi and Maskawa seems to give a value of the constant far below the present upper bound. It is interesting to note that both the left-right symmetric and spontaneous CP violation models have the tendency to predict values of the constant not so far from the experimental bound. The spontaneous CP violation model, in particular, appears to be the most promising candidate to give a value of the constant very close to the upper bound. Thus, the improvement of upper bound or measurement of DEMON by ultra cold neutron experiments is very desirable and will shed much light on the mechanism of CP violation. (N.K.)