Phenomenology of semi-leptonic reactions

In the leptonic sector, once we are given the values of a,G and Mz, there are no free parameters left (at least at Born approximation level) so that the entire phenomenology of leptonic reactions is calculable. 

In the hadronic sector, matters are not so clear cut. The coupling strengths Vij which involve four parameters are introduced at the quark level. Thus we have to find a convincing way to relate information at the quark level to the calculation of hadronic reactions. This step, in principle, involves the strong interactions and is therefore highly non-trivial. FVom this point of view the least difficult reactions are the semi-leptonic ones and we shall concentrate upon them in this chapter. 

As always with hadrons the strong interactions play a dominant role, which is largely not understood. Our weak interaction theory is very precise as far as quarks are concerned, but to translate this into precise statements about hadrons requires a model of the quark content of hadrons and the role of the quarks in scattering processes. 

One of the most remarkable discoveries of the past few years is the existence of a large cross-section for the inclusive reactions 

There is an elaborate and beautiful picture built upon this idea, the quark-parton model, which we shall investigate in detail in Chapters 15-17. In the framework of this model very precise and detailed tests of the standard model can be made, and we shall be content, at this point, to note that all aspects of the SM theory are consistent with experiments of the inclusive type up to the present. 

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Phenomenology of semi-leptonic reactions 10.1 Model independent tests... 

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