Model-Independent Determinations of B -> D l nu , D* l nu Form Factors

We present nonperturbative, model-independent parametrizations of the individual QCD form factors relevant to B -> D* l nu and B -> D l nu decays. These results follow from dispersion relations and analyticity, without recourse to heavy quark symmetry. To describe a form factor with two percent accuracy, three parameters are necessary, one of which is its normalization at zero recoil, F(1). We combine the individual form factors using heavy quark symmetry to extract values for the product |V_{cb}| F(1) from B -> D* l nu data with negligible extrapolation uncertainty.Comment: uses harvmac and epsf, 22 pages, 3 eps figures include

The Phenomenology of Inclusive Heavy-to-Light Sum Rules

By calculating the O(\alpha_s) corrections to inclusive heavy-to-light sum rules we find model independent upper and lower bounds on form factors for B to pi and B to rho. We use the bounds to rule out model predictions. Some models violate the bounds only for certain ranges of sum rule input parameters \bar{lambda} \simeq m_B-m_b and lambda_1, or for certain choices of model parameters, while others obey or violate the bounds irrespective of the inputs. We discuss the reliability and convergence of the bounds, point out their utility for extracting V_{ub}, and derive from them a new form factor scaling relation.Comment: 15 pages, 3 figures include

Lattice QCD Impact on Determination of the CKM Matrix

We review many lattice QCD calculations that impact the precise determination of the CKM matrix. We focus on decay constants and semileptonic form factors of both light ($\pi$ and K) and heavy-light ($D_{(s)}$ and $B_{(s)}$) mesons. Implication of $\Lambda_b$ form factors will be shown. When combined with experimental results for branching fractions and differential decay rates, the above calculations strongly constrain the first two rows of the CKM matrix. We discuss a long standing difference between $|V_{ub}|$ and $|V_{cb}|$ as determined from exclusive or inclusive decays.Comment: 10 pages, 6 figures, Proceedings of 16th Conference on Flavor Physics and CP Violation (FPCP 2018), July 14-18, 2018, Hyderabad, Indi

Resummation Methods at Finite Temperature: The Tadpole Way

We examine several resummation methods for computing higher order corrections to the finite temperature effective potential, in the context of a scalar $\phi^4$ theory. We show by explicit calculation to four loops that dressing the propagator, not the vertex, of the one-loop tadpole correctly counts ``daisy'' and ``super-daisy'' diagrams.Comment: 18 pages, LaTeX, CALT-68-1858, HUTP-93-A011, EFI-93-2

Bounding Heavy Meson Form Factors Using Inclusive Sum Rules

We utilize inclusive sum rules to construct both upper and lower bounds on the form factors for B to D, D*, rho, pi, omega, K and K* semi-leptonic and radiative decays. We include the leading nonperturbative 1/E corrections and point out cases when alpha_s corrections are equally important. We compute the alpha_s correction to the lower bound on the B to D* form factor f(w) at zero recoil, thereby constraining its normalization f(1) to within 6-8% of the upper bound. We show that the B to rho form factor a_+ is suppressed at small momentum transfer by either a factor of 1/E or alpha_s. These bounds can be used to rule out phenomenological models as well as to determine values for the CKM matrix elements once radiative corrections are included.Comment: LATEX file, 16 pages, 3 figures include

Semileptonic B and Lambda_b Decays and Local Duality in QCD

The inclusive and exclusive semileptonic decay distributions for b -> c decay are computed in the Shifman-Voloshin limit. The inclusive decay distributions (computed using an operator product expansion) depend on quark masses, and the exclusive decay distributions depend on hadron masses. Nevertheless, we show explicitly how the first two terms in the 1/m expansion match between the inclusive and exclusive decays. Agreement between the inclusive and exclusive decay rates requires a minimum smearing region of size Lambda_QCD before local duality holds in QCD. The alpha_s corrections to the inclusive and exclusive decay rates are also shown to agree to order (log m)/m^2. The alpha_s/m^2 corrections are used to obtain the alpha_s correction to Bjorken's inequality on the slope of the Isgur-Wise function.Comment: 22 pages, 3 eps figures, uses revtex (Revision: a discussion of radiative corrections to the bound K>0 of Section 7.B has been added; some typos, including labels in fig 2