Heavy flavour lifetimes

Aside from the spectator contribution to all charm particle decays (this is sometimes called W-radiation ), several approaches have been suggested in order to estimate possible corrections. Among these, we have  

All these mechanisms improve the agreement with the data to some extent. For detailed calculations, we refer the reader to the specialized literature (Gittelman, 1991 Kuhn et al., 1989 Basdevant et oL, 1987 and references therein). 

Before proceeding further however, let us show that naive arguments at least lead to the correct order of magnitude for both charm and bottom lifetimes. 

Using eqn (13.1.5) with me 1.6 GeV/c, recalling that IKs] 1, noting firom (13.2.1) or Fig. 13.13 which decays are Cabibbo allowed and taking colour into account (a factor of 3 for c — ud as compared with c — we find 

In the case of bottom decay, taking 4.5 GeV/c, V sin c 0.05 [see (9.2.6)] and recalling that a further channel (due to the t-lepton) contributes, we find 

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The subject of heavy flavours has e3q>anded tremendously in recent years stretching from the static properties (mainly spectroscopy, i.e. energy levels, lifetimes, branching ratios, decays, mixing etc.) of hadrons with one or more heavy quarks, e.g. bottom or charm, to more dynamical properties (like fragmentation, structure functions, jets etc.) and on to more exotic topics, e.g. production and decay of as yet undiscovered flavours like top, or speculations on a fourth generation or imphcations on Higgs or on non-standard effects and so on. 

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... 

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