Anathematizing the Guralnik and Manohar Inequality for \bar{\Lambda}

There is a recent claim by Guralnik and Manohar \cite{GM} to have established a rigorous lower bound on $\bar \Lambda$, the asymptotic difference between the mass of a heavy flavour {\em hadron} and that of the heavy flavour {\em quark}. We point out the flaw in their reasoning and discuss the underlying physical problem. An explicit counterexample to the GM bound is given; one can therefore not count on a refined proof to re-establish this bound. *********** Uses LaTeX No figures No macros file used.Comment: 7 pages Preprint UND-HEP-93-BIG07, CERN-TH.7091/9

D^0 - D^0-bar Oscillations as a Probe of Quark-Hadron Duality

It is usually argued that the Standard Model predicts slow D^0-\bar D^0 oscillations with \Delta M_D, \Delta \Gamma_D < 10^{-3}*\Gamma_D$ and that New Physics can reveal itself through \Delta M_D exceeding 10^{-3}*\Gamma_D. It is believed that the bulk of the effect is due to long distance dynamics that cannot be described at the quark level. We point out that in general the OPE yields soft GIM suppression scaling only like (m_s/\mu_{hadr})^2 and even like m_s/\mu_{hadr} rather than m_s^4/m_c^4 of the simple quark box diagram. Such contributions can actually yield \Delta M_D, \Delta \Gamma_D \sim O(10^{-3})*\Gamma_D without invoking additional long distance effects. They are reasonably suppressed as long as the OPE and local duality are qualitatively applicable in the 1/m_c expansion. We stress the importance of improving the sensitivity on \Delta \Gamma_D as well as \Delta M_D in a dedicated fashion as a laboratory for analyzing the onset of quark-hadron duality and comment on the recent preliminary study on \Delta \Gamma_D by the FOCUS group.Comment: 15 pages, LaTeX. Revised: A reference and a few clarifications in the text are added. A few inconsistencies in equations are eliminated. We found the standard contribution to Delta M_D to differ from the expression usually quoted in the literatur

On Extracting Heavy Quark Parameters from Moments with Cuts

We point out that applying the photon energy cut significantly modifies the moments of energy spectrum in B->X_s+gamma decays, with a certain class of effects not accounted for in the mostly used OPE expressions. This leads to a systematic bias in the extracted values of the b quark mass and other heavy quark parameters. The apparent b quark mass increases typically by 70MeV or more, together with an even more dramatic downward shift in the kinetic expectation value. Accounting for these cut-related shifts brings different measurements into a good agreement, when the OPE-based theory employs the robust approach. These nonperturbative effects are exponential in the effective hardness severely lowered by high cuts, and do not signify a breakdown of the 1/m_b expansion itself. Similar effects in semileptonic b->c decays are briefly addressed. We stress the utility of the second moment of E_gamma once these effects are incorporated.Comment: 8 pages, LaTeX, two figure. Contributed to the Lepton-Photon Conference, 2003, FNA

Strong interaction effects in semileptonic B decays

Strong interaction effects are addressed in connection to extracting |V_{cb}|. A comprehensive approach is described not relying on a 1/m_c expansion; it allows a percent accuracy without ad hoc assumptions about higher-order effects. An alternative to the M_X^2 variable is proposed improving convergence. Intrinsic hardness of integrated observables with a cut on E_\ell is discussed; it can be responsible for the behavior of reported by BaBar. Consequences of the proximity to the `BPS' limit are considered.Comment: 5 pages (two-column), LaTeX, uses espcrc2.sty. Talk given at ICHEP-2002, July 24-31 2002, Amsterda

Key Distributions for Charmless Semileptonic B Decay

We present theoretical predictions for a few phenomenologically interesting distributions in the semileptonic b->u decays which are affected by Fermi motion. The perturbative effects are incorporated at the one-loop level and appear to be very moderate. Our treatment of Fermi motion is based directly on QCD, being encoded in the universal distribution function F(x). The decay distributions in the charged lepton energy, invariant mass of hadrons, hadron energy, and q^2 are given. We note that typically about 90% of all decay events are expected to have M_X < M_D; this feature can be exploited in determination of |V_ub|.Comment: 9 pages, 6 figures (incorporated in the LaTeX file); plain LaTe

Non-factorization effects in heavy mesons and determination of |V_{ub}| from inclusive semileptonic B decays

The effects of spectator light quark in decays of heavy mesons are considered, which vanish in the limit of factorization of matrix elements of four-quark operators over the mesons. These effects include the difference of the total widths as well as of the semileptonic decay rates between the D^0 and D_s mesons and also a contribution to inclusive semileptonic decay rates of B^0 and B^\pm into the channel X_u l nu related to determination of the weak mixing parameter V_{ub}. If the observed difference of the lifetimes between D_s and D^0 mesons is attributed to non-factorizable terms, such terms can naturally give rise to a significant difference in inclusive semileptonic decay rates of these mesons, and to a light-flavor dependent contribution to decays B -> X_u l nu. The latter contribution affects mostly the upper part of the inclusive spectrum of the invariant mass of the lepton pair, and may significantly exceed the previously claimed in the literature theoretical uncertainty in determination of |V_{ub}|^2 from that part of the spectrum.Comment: 10 page

Interference Between Cabibbo Allowed and Doubly Forbidden Transitions in D\ra K_{S,L} + \pi 's Decays

Both Cabibbo allowed and doubly forbidden transitions contribute coherently to $D\rightarrow K_{S,L}+\pi 's$ decays. This leads to several intriguing and even quantitatively significant consequences, among them: (i) A difference between $\Gamma (D^+\rightarrow K_S \pi ^+)$ and $\Gamma (D^+\rightarrow K_L \pi ^+)$ and between $\Gamma (D^0\rightarrow K_S \pi ^0)$ and $\Gamma (D^0\rightarrow K_L \pi ^0)$ of roughly 10\% ; similarly $\Gamma (D^+\rightarrow [K_S\pi ^0]_{K^*} \pi ^+) \neq \frac{1}{4}\Gamma (D^+\rightarrow [K^-\pi ^+]_{K^*} \pi ^+)$, and more generally $\Gamma (D\rightarrow \bar K^0+\pi 's) \neq 2\Gamma (D\rightarrow K_S+\pi 's)$. (ii) A change in the relative phase between the isospin 3/2 and 1/2 amplitudes as extracted from the observed branching ratios for $D^+\rightarrow K_S\pi ^+$, $D^0\rightarrow K_S\pi ^0 ,\, K^-\pi ^+$. (iii) If New Physics intervenes to provide the required {\em weak} phase, then CP asymmetries of up to a few per cent can arise in $D^+\rightarrow K_S\pi ^+$ vs. $D^-\rightarrow K_S\pi ^-$, $D^0\rightarrow K_S\pi ^0$ vs. $\bar D^0\rightarrow K_S\pi ^0$, $D^+\rightarrow [K_S\pi ^0]_{K^*}\pi ^+$ vs. $D^-\rightarrow [K_S\pi ^0]_{K^*}\pi ^-$, etc.; an asymmetry of the same size, but opposite in sign occurs when the $K_S$ is replaced by a $K_L$ in the final state.Comment: 6 pages, latex, no figure

Moments of semileptonic B decay distributions in the 1/m_b expansion

We report the OPE-based predictions for a number of lepton energy and hadronic mass moments in the inclusive semileptonic B -> X_c \ell\nu decays with a lower cut on the charged lepton energy. We rely on the direct OPE approach where no expansion in the charm mass is employed and the theoretical input is a limited set of underlying OPE parameters including m_b and m_c. A Wilsonian treatment with a `hard' cutoff is applied using running low-scale masses m_Q(\mu) and kinetic expectation value \mu_\pi^2(\mu). This leaves for perturbative corrections only genuinely short-distance effects and makes them numerically small. Predictions are also given for the modified hadronic moments of the kinematic variable \cal N_X^2 which is a combination of M_X^2 and E_X. Measurement of such moments would allow a more reliable extraction of higher-order nonperturbative heavy quark parameters from experiment.Comment: 16 pages, LaTeX, three figure

Radiative Corrections to Nonleptonic Inclusive B Decays and the Semileptonic Branching Ratio of B Mesons

We calculate the radiative corrections to the nonleptonic inclusive B decay mode $b\to c ud$ taking into account the charm quark mass. The corrections increase the decay rate by (4--8)\%, depending on the renormalization point. Using these results, we obtain an improved theoretical prediction for the semileptonic branching ratio of B mesons. This talk relies on work done in collaboration with E. Bagan, V.M.\ Braun and P. Gosdzinsky.Comment: Talk given at QCD 94, Montpellier July 94, 5 p., TUM-T31-74/94, uses epsf.sty and a4wide.sty, 2 uuencoded PS figures include

CP Violation and the Cathedral Builders' Paradigm

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, $K_{\mu 3}$ 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.Comment: 20 pages, LaTex, Introductory Lecture given at CPconf2000, Intern. Conf. on CP Violation Physics, Sept. 18 - 22, 2000, Ferrara, Italy; few additions, in particular one reference to an early paper by Mohapatra on CP violatio