Enhancement of preasymptotic effects in inclusive beauty decays

We extend Voloshin's recent analysis of charmed and beauty hyperon decays based on SU(3) symmetry and heavy quark effective theory, by introducing a rather moderate model-dependence, in order to obtain more predictive power, e.g. the values of lifetimes of the (\Lambda_{b},\Xi_{b}) hyperon triplet and the lifetime of \Omega_{b}. In this way we obtain an improvement of the ratio \tau(\Lambda_{b})/\tau(B_{d}^{0}) \sim 0.9 and the hierarchy of lifetimes \tau(\Lambda_{b}) \simeq \tau(\Xi_{b}^{0}) < \tau(\Xi_{b}^{-}) < \tau(\Omega_{b}) with lifetimes of \Xi_{b}^{-} and \Omega_{b} exceeding the lifetime of \Lambda_{b} by 22% and 35%, respectively.Comment: Latex2e, 12 pages, 3 eps figures include

The Lifetimes of Heavy Flavour Hadrons - a Case Study in Quark-Hadron Duality

The status of heavy quark expansions for charm and beauty lifetime ratios is reviewed. Taking note of the surprising semiquantitative success of this description for charm hadrons I interprete the new data on $\tau (D_s)$ and re-iterate the call for more precise measurements of $\tau (\Xi_c^{0,+})$ and $\tau (\Omega_c)$. A slightly larger $B^-$ than $B_d$ lifetime is starting to emerge as predicted; the largest lifetime difference in the beauty sector, namely in $\tau (B_c)$ vs. $\tau (B)$ has correctly been predicted; the problem posed by the short $\Lambda_b$ lifetime remains. The need for more accurate data also on $\tau (B_s)$ and $\tau (\Xi_b^{-,0})$ is emphasized. I discuss quark-hadron duality as the central theoretical issue at stake here.Comment: 12 pages, LATEX, no figures, 2 tables; slightly extended version of Invited Talk given at the 3rd International Conference on B Physics and CP Violation, Taipeh, Taiwan, Dec. 3 - 7, 199

Theory of Beauty Lifetimes

A critical review of the theoretical understanding of the lifetimes of beauty hadrons is given. A model-independent analysis using the heavy-quark expansion allows for a description of the lifetime ratios tau(B-)/tau(B0) and tau(Lambda_b)/tau(B0) in a small region of parameter space. It is demonstrated that the lifetime ratio tau(B-)/tau(B0) cannot be used to extract the decay constant of the B meson. Implications for the semileptonic branching ratio and charm yield in B decays are pointed out.Comment: 13 pages, 4 figures embedded. Invited talk presented at the Second International Conference on B Physics and CP Violation, Honolulu, Hawaii, 24-27 March 199

Lifetimes of Heavy-Flavour Hadrons -- Whence and Whither?

A theoretical treatment for the weak decays of heavy-flavour hadrons has been developed that is genuinely based on QCD. Its methodology as it applies to total lifetimes and the underlying theoretical issues are sketched. Predictions are compared with present data. One discrepancy emerges: the beauty baryon lifetime appears to be significantly shorter than expected. The ramifications of those findings are analyzed in detail.Comment: 15 pages, no figures, LATEX, two references added and new information concerning a lower charm content in B decays incorporate

Spectator Effects in Inclusive Decays of Beauty Hadrons

We present a model-independent study of spectator effects, which are responsible for the lifetime differences between beauty hadrons. These effects can be parametrized in terms of hadronic matrix elements of four four-quark operators. For $B$ mesons, the coefficients of the non-factorizable operators turn out to be much larger than those of the factorizable ones, limiting considerably the usefulness of the vacuum insertion approximation. Non-factorizable contributions to the lifetime ratio $\tau(B^-)/\tau(B_d)$ could naturally be of order 10--20%, and not even the sign of these contributions can be predicted at present. In the case of the $\Lambda_b$ baryon, heavy-quark symmetry is used to reduce the number of independent matrix elements from four to two. In order to explain the large deviation from unity in the experimental result for $\tau(\Lambda_b)/\tau(B_d)$, it is necessary that these baryon matrix elements be much larger than those estimated in quark models. We have also reexamined the theoretical predictions for the semileptonic branching ratio of $B$ mesons and charm counting, finding that, given the present theoretical and experimental uncertainties, there is no significant discrepancy with experiment.Comment: 32 pages, 5 postscript figures included, revised version to appear in Nuclear Physics

Perspectives on Heavy Quark 98

I summarize and comment upon some highlights of HQ98, the Workshop on Heavy Quarks (strange, charm, and beauty) at Fixed Target.Comment: Summary talk at HQ98. 21 pages, uses aipproc (included

Inclusive Charmed-Baryon Decays and Lifetimes

We have quantitatively reanalyzed the inclusive charmed-baryon decays. New ingredients are the Voloshin preasymptotic effects in semileptonic decays and the Cabibbo-subleading contributions to both semileptonic and nonleptonic decays. It has been found that the Cabbibo-subleading Voloshin contribution essentially improves the theoretical semileptonic branching ratio of $\Lambda_c^{+}$, in agreement with experiment. The semileptonic branching ratios for $\Xi_c^{+}$ and $\Omega_c^{0}$ are found to be large, i.e., of the order of 20%. The lifetimes hierarchy is in a good qualitative and even quantitative agreement with experiment except for the $\Xi_c^{+}$ lifetime, which is somewhat smaller than the experimental value. Future measurements, especially measurements of the semileptonic branching ratios for $\Omega_c^{0}$, $\Xi_c^{+}$ and $\Xi_c^{0}$ should be decisive for the check of this approach.Comment: 13 pages, Latex, 3 figures included, shortened version, to appear in Z.Phys.

Beauty Hadron Lifetimes and B-Meson CP-Violation Parameters from Lattice QCD

The present status of the theoretical estimates of beauty hadron lifetime ratios and of width differences and CP-violation parameters in $B_d$ and $B_s$ systems is reviewed. In the last two years accurate lattice calculations and next-to-leading order perturbative computations have improved these theoretical predictions, leading to the following updated results: \tau(B^+)/\tau(B_d)=1.06 +- 0.02, \tau(B_s)/\tau(B_d)=1.00 +- 0.01, \tau(\Lambda_b)/\tau(B_d)=0.88 +- 0.05, \Delta \Gamma_{d}/\Gamma_{d} = (2.42 +- 0.59)10^{-3}, \Delta \Gamma_{s}/\Gamma_{s} = (7.4 +- 2.4)10^{-2}, |(q/p)_d|-1=(2.96 +- 0.67) 10^{-4}$ and |(q/p)_s|-1=-(1.28 +- 0.28) 10^{-5}Comment: Invited talk at "International Europhysics Conference on High-Energy Physics" (HEP 2003), Aachen, Germany, 17-23 Jul 200