Charm mesons hadronic decays

If we assume charm to be a good quantum number under strong and electromagnetic interaction (see Section 13.3), the pseudo-scalar chmm mesons D, D and Df can only decay weakly into old mesons. By contrast, D s can decay both strongly and electromagnetically whereas only the latter mode is available to T> due to its mass threshold, as can be seen from Table 13.1. The naive expectation that heavy flavoured hadron decays are entirely determined by the so-called spectator diagram (Fig. 13.13) leads to immediate predictions for the lifetimes of these... 

As we shall soon see, the total decay rate of D and (into hadrons) can be estimated to be of the order of 10 — 10 s so that the purely leptonic decay rate of charm mesons leads to branching ratios which are, at most, of order 10 — 10 and can, therefore, be neglected. Indeed up to the present, none of the leptonic decays has been observed (on this question, the Particle Data Group (1992) reports BR( > — ... 

Semi-leptonic and hadronic decays of charm mesons... 

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. 

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