Semi-leptonic and hadronic decays of charm mesons

3 Semi-leptonic and hadronic decays of charm mesons 

Semi-leptonic decays should, in principle, provide the best way to test our ideas about charm currents since the hadronic current appears only once and is multiplied by the well-known leptonic part. 

Semi-leptonic decays of charm mesons with an electron in the final state were first observed at DESY by the DASP collaboration shortly after the first evidence for charm had been reported in hadronic decays. 

Let us consider first semi-leptonic three-body decays. It follows from Fig. 13.13 that possible transitions obey the following selection rules Cabibbo allowed (i.e. proportional to cos 0c) 

Taking into account the different Cabibbo structure K has a 

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