ABSTRACT
In the previous two chapters, we have studied the basic techniques in the construction of a supersymmetric Lagrangian. SUSY cannot, however, be an exact symmetry of Nature. In fact, if it were, it would imply the existence of, e.g., a selectron with the same mass as the electron, ∼ $ \sim $ https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315367903/c2682a74-a79a-4ae8-b55f-fb03894f6bcd/content/inline-math3_1.tif"/> 0.5 MeV, and squarks with the same mass of quarks, for which there is no experimental evidence. Thus, in order for SUSY to play a role in particle physics, it must be a broken symmetry at energies at least of the order of the EW scale. As any other symmetry, SUSY can be broken either spontaneously, dynamically or explicitly.
