Heavy flavour masses

As compared with the case of hidden charm, discussed in the previous chapters, the spectroscopy of heavy flavoured particles, especially charm 

Despite this, the masses of charm mesons were predicted (by, for example, de Rujula, Georgi and Glashow, 1975) before their actual discovery. That these predictions (Table 13.3) are quite reasonable can be seen by comparing with the experimental data reported in Table 13.1. 

The accuracy of present calculations is much higher (see Godfrey and Isgur, 1985) but the theoretical basis and limitations are much the same as discussed in Chapter 12. 

Some calculations use very general arguments to derive bounds for as yet undiscovered heavy flavoured particles. For example, Anselmino et al., (1990a) isolate the effects of colour-hyperflne terms and use experimental information to make predictions about the masses of baryons containing at least one heavy quark. Typical results are the predictions 64 ft — ftc 107 MeV/c, and 23 ftj — ftj, 39 MeV/c. These imply that ft and ftj cannot decay strongly. By the same technique one finds also 23 EJ — Efc 39 MeV/c so EJ cannot decay strongly into Ej, but both decay strongly into Aj,. 

To a large degree the considerations that follow can be extended to bottom with only minor changes. We will continue to refer to charm for simplicity. 

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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... 

A new chapter on heavy flavour physics has been initiated at LEP in its studies of decays. The main motivation for heavy flavour searches, i.e. the quest for top (and Higgs), has been frustrating so far and we have repeatedly commented about the top mass limits set by LEP [eqn (8.6.20)] ... 

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