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Register a new userRegge asymptotics and color suppressed heavy meson decays
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We discuss a possible generation of color suppressed B-decays amplitudes through a soft final state interaction. As a typical example, we consider in detail the decay $ bar{B}^{0} rightarrow D^{0} pi^{0} $ (and also $ bar{B}^{0} rightarrow 2 pi^{0} $). We show that in the approximation of the two particle unitarity and at zero order in $ alpha_{s} $ this process can be related to the weak decay $ bar{B}^{0} rightarrow D^{+} pi^{-} $ followed by the strong charge exchange scattering in the Regge kinematics. We estimate the amplitude of this process using the light cone QCD sum rule technique and find that it is supppressed as a power of $ 1/m_{B} $ in comparison to the amplitude generated by the effective non-leptonic Hamiltonian, but remains important for the physical value of $m_{B}$.
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A phenomenological analysis of the scalar meson f0(980) is performed that relies on the quasi-two body decays D and Ds -> f0(980)P, with P=pi, K. The two-body branching ratios are deduced from experimental data on D or Ds -> pi pi pi, K Kbar pi and from the f0(980) -> pi+ pi- and f0(980) -> K+ K- branching fractions. Within a covariant quark model, the scalar form factors F0(q2) for the transitions D and Ds -> f0(980) are computed. The weak D decay amplitudes, in which these form factors enter, are obtained in the naive factorization approach assuming a quark-antiquark state for the scalar and pseudoscalar mesons. They allow to extract information on the f0(980) wave function in terms of u-ubar, d-dbar and s-sbar pairs as well as on the mixing angle between the strange and non-strange components. The weak transition form factors are modeled by the one-loop triangular diagram using two different relativistic approaches: covariant light-front dynamics and dispersion relations. We use the information found on the f0(980) structure to evaluate the scalar and vector form factors in the transitions D and Ds -> f0(980), as well as to make predictions for B and Bs -> f0(980), for the entire kinematically allowed momentum range of q2.
I discuss the interplay of infrared sensitivity in large order perturbative expansions with the presence of explicit nonperturbative corrections in the context of heavy quark expansions. The main focus is on inclusive decays and the status of the kinetic energy of the heavy quark. This talk summarizes work done with Braun and Zakharov.
We present a general study on exclusive semileptonic decays of heavy (B, D, B_s) to light (pi, rho, K, K^*) mesons in the framework of effective field theory of heavy quark. Transition matrix elements of these decays can be systematically characterized by a set of wave functions which are independent of the heavy quark mass except for the implicit scale dependence. Form factors for all these decays are calculated consistently within the effective theory framework using the light cone sum rule method at the leading order of 1/m_Q expansion. The branching ratios of these decays are evaluated, and the heavy and light flavor symmetry breaking effects are investigated. We also give comparison of our results and the predictions from other approaches, among which are the relations proposed recently in the framework of large energy effective theory.
We calculate the form factors for the semileptonic decays $B_sto Kell u$ and $Bto Kellell$ with lattice QCD. We work at several lattice spacings and a range of light quark masses, using the MILC 2+1-flavor asqtad ensembles. We use the Fermilab method for the $b$ quark. We obtain chiral-continuum extrapolations for $E_K$ up to $sim1.2$ GeV and then extend to the entire kinematic range with the model-independent $z$ expansion.
We revisit QCD calculations of radiative heavy meson decay form factors by including the subleading power corrections from the twist-two photon distribution amplitude at next-to-leading-order in $alpha_s$ with the method of the light-cone sum rules (LCSR). The desired hard-collinear factorization formula for the vacuum-to-photon correlation function with the interpolating currents for two heavy mesons is constructed with the operator-product-expansion technique in the presence of evanescent operators. Applying the background field approach, the higher twist corrections from both the two-particle and three-particle photon distribution amplitudes are further computed in the LCSR framework at leading-order in QCD, up to the twist-four accuracy. Combining the leading power point-like photon contribution at tree level and the subleading power resolved photon corrections from the newly derived LCSR, we update theory predictions for the nonperturbative couplings describing the electromagnetic decay processes of the heavy mesons $H^{ast , pm} to H^{pm} , gamma$, $H^{ast , 0} to H^{0} , gamma$, $H_s^{ast , pm} to H_s^{pm} , gamma$ (with $H=D, , B$). Furthermore, we perform an exploratory comparisons of our sum rule computations of the heavy-meson magnetic couplings with the previous determinations based upon different QCD approaches and phenomenological models.
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