Improved bounds on some weak amplitudes from the b lifetime

Physical Review Letters, 2006

A class of previously unknown strong-interaction corrections is found to enhance the rate of non-leptonic decays of the b quark by 5-8 percent. This effect decreases the predicted fraction of semi-leptonic decays and brings it into fair agreement with experimental results. As well as solving a long-standing puzzle of measurements disagreeing with the Standard Model prediction, our work suggests a way for future precise studies of non-leptonic b quark decays and their application to searching for "new physics."

Physics Letters B, 2015

We present the results of a calculation of the perturbative QCD corrections for the semileptonic inclusive width of a heavy flavored meson. Within the Heavy Quark Expansion we analytically compute the QCD correction to the coefficient of power suppressed contribution of the chromo-magnetic operator in the limit of vanishing mass of the final state quark. The important phenomenological applications are decays of bottom mesons, and to the less extend, charmed mesons.

arXiv (Cornell University), 1993

We present a systematic analysis of the B (*) → π ℓ ν weak decay form factors to order 1/m b in the heavy quark effective theory, including a discussion of renormalization group effects. These processes are described by a set of ten universal functions (two at leading order, and eight at order 1/m b), which are defined in terms of matrix elements of operators in the effective theory. In the soft pion limit, the effective theory yields normalization conditions for these functions, which generalize the well-known current algebra relations derived from the combination of heavy quark and chiral symmetries to nextto-leading order in 1/m b. In particular, the effects of the nearby B *-pole are correctly contained in the form factors of the effective theory. We discuss the prospects for a model independent determination of |V ub | and the BB * π coupling constant from these processes.

1993

We present a systematic analysis of the B (*) → π ℓ ν weak decay form factors to order 1/m b in the heavy quark effective theory, including a discussion of renormalization group effects. These processes are described by a set of ten universal functions (two at leading order, and eight at order 1/m b), which are defined in terms of matrix elements of operators in the effective theory. In the soft pion limit, the effective theory yields normalization conditions for these functions, which generalize the well-known current algebra relations derived from the combination of heavy quark and chiral symmetries to nextto-leading order in 1/m b. In particular, the effects of the nearby B *-pole are correctly contained in the form factors of the effective theory. We discuss the prospects for a model independent determination of |V ub | and the BB * π coupling constant from these processes.

Physical Review Letters, 1983

Modern Physics Letters A, 1998

The form factors for the weak currents between B and light mesons are studied by relating them to the corresponding D form factors at q^2_{max} according to HQET, by evaluating them at q2=0 by QCD sum rules, and by assuming a polar q2 dependence. The results found are consistent with the information obtained from exclusive non-leptonic two-body decays and, with

A field theoretic description for inclusive semileptonic B meson decays is formulated. We argue that large regions of the phase spaces for the decays are dominated by distances near the light cone. The light-cone dominance allows to incorporate nonperturbative QCD effects in a distribution function. A one-to-one correspondence with the heavy quark effective theory is developed, which can estimate the first two moments of the distribution function. These conditions are useful but not restrictive enough to specify the distribution function, which must still be determined from experiment. Several model-independent predictions, such as scaling, sum rules of the hadronic structure functions and relations among them, are made. General formulas for the differential decay rates on several variables are presented, which are used for calculating the electron energy spectra with an Ansatz for the light-cone distribution function.

Nuclear Physics B, 2005

We study the branching ratios of rare K and B decays in models with minimal flavour violation, using the presently available information from the universal unitarity triangle analysis and from the measurements of Br(B → X s γ), Br(B → X s l + l − ) and Br(K + → π + νν). We find the following upper bounds: Br(K + → π + νν) < 11.9 × 10 −11 , Br(K L → π 0 νν) < 4.6 × 10 −11 , Br(

Physical Review Letters, 2006

We present the first experimental limits on high-q 2 contributions to charmless semileptonic B decays of the form expected from the Weak Annihilation (WA) decay mechanism. Such contributions could bias determinations of |V ub | from inclusive measurements of B → X u ℓν. Using a wide range of models based on available theoretical input we set a limit of Γ WA /Γ b→u < 7.4% (90% confidence level) on the WA fraction, and assess the impact on previous inclusive determinations of |V ub |.

Journal of High Energy Physics

We study the decay B --&gt; K l^+ l^- for l = e,mu,tau with a softly recoiling kaon, that is, for high dilepton invariant masses sqrt{q^2} of the order of the b-quark mass. This kinematic region can be treated within an operator product expansion and simplified using heavy quark symmetry, leading to systematic predictions for heavy-to-light processes such as B --&gt; K^(*) l^+ l^-. We show that the decay rates of both B --&gt; K^* l^+ l^- and B --&gt; K l^+ l^- decays into light leptons depend on a common combination of short-distance coefficients. The corresponding CP-asymmetries are hence identical. Furthermore we present low recoil predictions for B --&gt; K l^+ l^- observables, including the flat term in the angular distribution which becomes sizable for taus. We work out model-independently the constraints on Delta B = 1 operators using the most recent data from the experiments BaBar, Belle, CDF and LHCb. For constructive interference with the standard model, generic new physic...