Breit-Wigner amplitude

The complex energy, 2 of Eq. (5) is normally understood in fhe context of resonance scattering theory as the complex pole in the Breit-Wigner amplitude, or in the S-matrix, or in the optical potential of Feshbach s fheory," or in the Green s function, e.g.. Refs. [2,6-8]. 

The explanation for both phenomena is based on the Breit-Wigner model for resonant tunneling. In the vicinity of a narrow isolated resonance (i.e. jn < jcn — en i )j the transition probability amplitude is given... 

The phase of the transition probability amplitude, arg(t(J5)), changes by 7T when t E) exhibits a maximum (see Fig. 9(a)). This well-known phenomenon can be explained by the Breit-Wigner model for resonant tunneling. 

Assuming that Fig. 11.9 (a) dominates near the resonance mass and parametrizing the resonant amplitude a la Breit-Wigner (see, for example, Blatt and Weisskopf, 1979), for the reaction... 

Combining the Mdller factor and the Wigner rotation matrix, the proton-nucleon t-matrix amplitudes in the pyl COM Breit frame are obtained from the matrix operation [Ra 85]... 

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