We argue that the Large Energy Effective Theory (LEET), originally proposed by Dugan and Grinstein, is applicable to exclusive semileptonic, radiative and rare heavy-to-light transitions in the region where the energy release E is large compared to the strong interaction scale and to the mass of the final hadron, i.e. for q 2 not close to the zero-recoil point. We derive the Effective Lagrangian from the QCD one, and show that in the limit of heavy mass M for the initial hadron and large energy E for the final one, the heavy and light quark fields behave as two-component spinors. Neglecting QCD short-distance corrections, this implies that there are only three form factors describing all the pseudoscalar to pseudoscalar or vector weak current matrix elements. We argue that the dependence of these form factors with respect to M and E should be factorizable, the M -dependence ( √ M ) being derived from the usual heavy quark expansion while the E-dependence is controlled by the behaviour of the light-cone distribution amplitude near the end-point u ∼ 1. The usual expectation of the ∼ (1 − u) behaviour leads to a 1/E 2 scaling law, that is a dipole form in q 2 . We also show explicitly that in the appropriate limit, the Light-Cone Sum Rule method satisfies our general relations as well as the scaling laws in M and E of the form factors, and obtain very compact and simple expressions for the latter. Finally we note that this formalism gives theoretical support to the quark model-inspired methods existing in the literature.

We explicitly formulate the vacuum quark-pair-creation model (QPC) of strong-interaction vertices (Micu, Carlitz and Kislinger) in terms of the harmonic-oscillator spatial-SU(6) wave functions and an explicit vacuum quark-antiquark-pair transition matrix (both displaying the quark internal momenta). The coupling constants are expressed as functions of masses and the oscillator radius. The structure of the formulas is in agreement with the expressions coming from VMD (vector-meson dominance) and PCAC (partial conservation of axial-vector current), and the quark-model calculation of leptonic decays. We carefully investigate the relation of this QPC model with the additive quark model with elementary meson emission, which is known to explain most of the hadronic decay? We show that we recover this model in a given limit. It is shown that in this limit, a term G ( i ) . ( g , -k i ) (depending on the internal quark momentum) appears in place of the usual Z(i).$, term; the additional contribution is similar to the well-known "recoil" term of Mitra and Ross. The main limits of the model lie (i) in the presence of a phenomenological pair-creation constant and (ii) in the nonrelativistic character of the treatment. A critical test of our model is provided by prediction of the decay-products polarization. We find a striking agreement with experiment for the crucial A , and B decays. We make a comparison with the parameter-dependent model of Colglazier and Rosner.

No abstract

No abstract

Using the Bogoliubov-Valatin variational method, we show that the chiral-invariant vacuum is unstable for a color, fourth-component vector powerlike potential r a ( 0

No abstract

Once chosen the dynamics in one frame, the rest frame in this paper, the Bakamjian and Thomas method allows to define relativistic quark models in any frame. These models have been shown to provide, in the infinite quark mass limit, fully covariant current form factors as matrix elements of the quark current operator. In this paper we use the rest frame dynamics fitted from the meson spectrum by various authors, already shown to provide a reasonable value for ρ 2 . From the general formulae for the scaling invariant form factors ξ (n) (w), τ1/2 (w) and τ (n) 3/2 (w), we predict quantitavely the B semileptonic branching ratios to the ground state and orbitally excited charmed mesons D, D * and D * * . We check Bjorken's sum rule and discuss the respective contributions to it. We find ξ(w) ≃ (2/(1 + w)) 2 , resulting from the fact that the ground state wave function is Coulomb-like. We also find τ 3/2 ≃ 0.5(2/(1+w)) 3 and τ 1/2 (w) ≪ τ 3/2 (w). Very small branching ratios into j = 1/2 orbitally excited D's results. The overall agreement with experiment is rather good within the present accuracy which is poor for the orbitally excited charmed mesons. We predict a ratio Br(B → D * 2 lν)/Br(B → D1lν) = 1.55 ± 0.15 as a mere consequence of the heavy quark symmetry. If some faint experimental indications that Br(B → D1lν) ≃ Br(B → D * 2 lν) were confirmed, it would indicate a sizeable O(1/mc) correction. LPTHE Orsay-97/19PCCF RI 9707 hep-ph/9706265

The Bogoliubov-Valatin variational method is used to show analytically that the chiralinvariant vacuum is unstable for a color, fourth-component vector linear potential. The physical origin of the instability is the fermion self-energy, which is negative and overcomes the positive potential energy, destabilizing the vacuum by pair condensation.