arXiv subjects
Publications and source records attributed to I. I. Bigi.
It has been suggested that the observed $D_s - D^0$ lifetime difference can be `understood' as due to $SU(3)_{Fl}$ breaking in the phase spaces for the exclusive $D^0$ and $D_s$ channels `removing' the need for weak annihilation. It is pointed out that several of the statements in this argument are misleading or even inconsistent with a state-of-the-art description of heavy flavour decays based on the operator product expansion.
The $B$ factories are expected to provide huge samples of single $B$ decay events with little background by reconstructing one of the $B$ mesons produced in $Υ(4S)$ decays. This represents a new experimental paradigm: such samples will allow to make measurements of a quality previously thought unrealistic. As example we discuss how absolute branching ratios for exclusive as well as inclusive charm baryon decays can be extracted. One starts out by observing decays like $B^- \to \bar p X$ as a signature for $B^- \to Λ_c \bar p X$ etc. and then exploits various correlations of the flavour of the $B$ meson with the baryon number of the (anti)proton and other observables like the charge of a lepton, baryon number of another baryon etc. An integrated luminosity of about 500 $fb^{-1}$ as could be available by 2005 should be sufficient for the task.
After sketching heavy quark expansions as applied to heavy flavour decays I emphasize the relevance of nonperturbative dynamics at the charm scale for exclusive $b\to c$ modes. I address the issue of quark-hadron duality for charm and discuss both the experimental and theoretical status of $D^0-\bar D^0$ oscillations. Finally I argue that comprehensive CP studies of charm decays provide novel portals to New Physics and suggest benchmark figures for desirable sensitivities.
After a short review of the theoretical tools available to describe heavy flavour physics I sketch the present profile of the weak dynamics of charm hadrons with respect to lifetimes, oscillations and CP violation. I argue that comprehensive studies of charm decays provide novel portals to New Physics and suggest some benchmark figures for desirable sensitivities.
After a reminder about how $ΔS\neq 0$ physics has been instrumental for the development of the Standard Model I sketch theoretical technologies for dealing with nonperturbative QCD in heavy flavour decays and state predictions for CP odd effects as they were made in 1998. I review the exciting developments in heavy flavour physics as presented at this conference. A central message is presented in the `Rio Manifesto' where I recapitulate the lessons we have learnt from charm physics, point out the special role future dedicated charm studies can play in revealing the presence of New Physics and give an introduction to the relevant phenomenology focussed on CP studies.
After summarizing the status concerning CP violation in 1998 I describe the exciting developments of the last two years and extrapolate to the future. I comment on recent lessons about T and CPT invariance maninly from CPLEAR and emphasize the potential of finding New Physics by analyzing $K_{μ3}$ and charm decays and searching for electric dipole moments.
Pointing out the profound and unique nature of CP violation, I sketch its basic phenomenology, its CKM prescription and QCD technologies relevant for heavy flavour physics. After emphasizing the paradigmatic character of the establishment of direct CP violation I turn to the future, namely indirect searches for New Physics in electric dipole moments, $K_{μ3}$ decays and charm transitions on one hand and in beauty decays on the other; these are described as exciting adventures with novel challenges not encountered before.
After pointing out the amazing success of the CKM description in accommodating the phenomenology of flavour changing neutral currents I review the status of theoretical technologies for extracting CKM parameters from data. I sketch novel directions, namely attempts to deal with quark-hadron duality in a (semi)quantitative way and to develop a QCD description of two-body modes of $B$ mesons. After commenting on predictions for $ε^{\prime}/ε$ and CP asymmetries in B decays I address indirect probes for New Physics in $D^0$ oscillations and CP violation, in $K_{μ3}$ decays and electric dipole moments. I describe in which way searching for New Physics in B decays provides an exciting adventure with novel challenges not encountered before.
Even in 2010 the CKM parameters $V_{cs}$, $V_{cd}$ and $V_{ub}$ will be known with less than desirable accuracy; the discovery potential for New Physics in charm decays -- in particular their CP asymmetries -- will be far from exhausted; important tests of our theoretical tools will not have been performed. I sketch the impact a $ν$fact could have in these areas.
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 $τ(D_s)$ and re-iterate the call for more precise measurements of $τ(Ξ_c^{0,+})$ and $τ(Ω_c)$. A slightly larger $B^-$ than $B_d$ lifetime is starting to emerge as predicted; the largest lifetime difference in the beauty sector, namely in $τ(B_c)$ vs. $τ(B)$ has correctly been predicted; the problem posed by the short $Λ_b$ lifetime remains. The need for more accurate data also on $τ(B_s)$ and $τ(Ξ_b^{-,0})$ is emphasized. I discuss quark-hadron duality as the central theoretical issue at stake here.
A comprehensive program of \cp~studies in heavy flavour decays has to go beyond observing large \cp asymmetries in nonleptonic B decays and finding that the sum of the three angles of the KM triangle is consistent with 180$^{\circ}$. There are many more correlations between observables encoded in the KM matrix; those can be expressed through five KM triangles in addition to the one usually considered. To test the completeness of the KM description one has to obtain a highly overconstrained data set sensitive to ${\cal O}(λ^2)$ effects with $λ= \sin θ_C$. Those fall into two categories: (i) Certain large angles agree to leading order only, yet differ in order $λ^2$ in a characteristic way. (ii) Two observables angles are - for reasons specific to the KM ansatz - ${\cal O}(λ^2)$ and ${\cal O}(λ^4)$ thus generating an asymmetry of a few percent and of about 0.1 %, respectively. The former can be measured in $B_s \to ψη, ψϕ$ {\em without} hadronic uncertainty, the latter in Cabibbo suppressed D decays. The intervention of New Physics could boost these effects by an order of magnitude. A special case is provided by $D^+ \to K_{S,L}π^+$ vs. $D^- \to K_{S,L}π^-$. Finally, \cp~asymmetries involving $D^0 - \bar D^0$ oscillations could reach observable levels only due to New Physics.
Data from the CPLEAR collaboration coupled with the assumption that the Bell-Steinberger relation holds have provided {\em direct} evidence for \ot~violation. In this note we investigate what we can say about \ot~violation {\em without} such an assumption. We show that both the modulus and the phase of $η_{+-}$ can be reproduced with \ot~{\em invariant} dynamics through finetuning \cpt~breaking. The large \ot~odd correlation observed by the KTeV collaboration in $K_L \to π^+π^- e^+ e^-$ thus does not yield direct evidence for \ot~violation. In such a world the phase of $\frac{ε'}ε$ is $δ_2-δ_0-ϕ_{SW}\sim -(85.5\pm 4)^\circ$. Also, $K^{\pm} \to π^{\pm} π^0$ could exhibit a \cpt~asymmetry of up to few$\times 10^{-3}$ without upsetting any known bound.
Heavy Quark Expansions for semileptonic decays of beauty hadrons are briefly reviewed. I analyze how $|V(cb)|$ can be extracted from the semileptonic width of $B$ mesons, the average semileptonic width of all weakly decaying beauty hadrons and from $B \ra l νD^*$ at zero recoil. Special attention is paid to present theoretical uncertainties (including correlations among them) and on how to reduce them in the future. Finally I will comment on theoretical uncertainties in $|V(ub)/V(cb)|$.
Several experiments are about to measure the CP asymmetry for $B \to ψK_S$ and other decays. The standard model together with the Kobayashi-Maskawa ansatz for CP violation predicts the sign as well as the magnitude for this asymmetry. In this note we elucidate the physics and conventions which lead to the prediction for the sign of the asymmetry.
The heavy quark expansion implemented through an operator product expansion provides us with a treatment of inclusive decays of beauty and charm hadrons that is genuinely derived from QCD,though it requires one additional assumption, namely that of 'local' quark-hadron duality. Subtleties in the application of factorization to hadronic expectation values are pointed out. The observed pattern in the charm lifetime ratios is reproduced in a semi-quantitative manner. The ratio $τ(Λ_b)/τ(B_d)$ cannot be pushed significantly below 0.9 -- unless one invokes a new hitherto unknown paradigm for evaluating baryonic matrix elements. One confidently predicts $τ(B^-)$ to exceed $τ(B_d)$ by several percent only. Failure of those predictions would force us to pay a hefty theoretical price, namely ultimately to abandon local duality as a practical concept.
Phenomenological models of heavy flavour decays differ significantly in their predictions of global features of $B_c$ decays, like the $B_c$ lifetime or the relative weight of $c\ra s$ and $b\ra c$ transitions. The $1/m_Q$ expansion which is directly based on QCD allows predictions on the pattern to be expected, namely $τ(B_c)$ to lie well below 1 psec with $c\ra s$ dominating over $b\ra c$ and a reduced semileptonic branching ratio. Due to interference effects one also predicts a lower charm content in the final states of $B_c$ decays than naively anticipated. The numerical aspect of the predictions, however, has to be viewed with considerable caution since one cannot expect the $1/m_c$ expansion to converge readily for $ΔC=1$ transitions.
Over the last few years a theoretical treatment for the weak decays of heavy-flavour hadrons has been developed that is genuinely based on QCD. Its methodology is described as it applies to total lifetimes, and the underlying theoretical issues are discussed. Theoretical expectations are compared with present data. One discrepancy emerges: the beauty baryon lifetime appears to be significantly shorter than predicted. The ramifications of those findings are analyzed in detail, and future refinements are described.
The recent progress in our understanding of heavy-flavour decays allows us to define more reliably which future measurements on charm decays are needed to further advance our understanding of QCD and to get our theoretical tools ready for treating beauty decays. After sketching the theoretical landscape I list those required measurements. I argue that some -- in particular those concerning inclusive semileptonic charm decays and their lepton spectra -- can presumably be performed only at a tau-charm factory.