PhD thesis - CP3-Origins

Technicolor 39A particle with this small mass should be seen in the experiments, thus the mass hasto be bigger. We can increase the mass by making Λ ET C to be smaller. On the otherhand large suppression of the flavor changing neutral currents requires just the opposite.Again, we need something more.Walking DynamicsIntuitively the problem can be solved if there is a great difference between condensateat scales Λ T C and Λ ET C , since m f ∝ 〈 ¯QQ〉 ET C . Because of this, we can achieve largeenough masses and suppressed flavor changing neutral currents at the same time. Thisidea was first introduced in reference [43] without providing an explicit model.The coupling constant of a given Yang-Mills theory can behave also differently than inQCD, see Figure 4.1. If the β-function has a non-trivial fixed point α ∗ , the scale evolutionof the theory stops when it flows to this point β(α ∗ ) = 0. If we formulate the theory suchthat it almost reaches the fixed point, its scale evolution slows down near fixed pointbut does not stop. Technicolor model with β(µ) ≪ 1 between Λ T C ≤ µ ≤ Λ ET C is calledwalking technicolor model.Βg 2walkingQCDlikeFigure 4.1.: Different possible beta functions for SU(N) gauge theory.It is also important that α ∗ α c where the subscript refers to the critical value atwhich the condensate forms. If the fixed point is achieved first, the scale evolution stopsand the condensate can not form. On the other hand, formation of the condensate can