arXiv subjects
Publications and source records attributed to G. Stoll.
A model-independent way of computing the mass corrections of vector-meson distribution amplitudes is given. The method is based on resummation of (next-to-)leading twist local operator.
A review of light-cone, covariant and gauge-invariant wave-functions of mesons is presented. They are basic non-perturbative objects needed for hard exclusive processes and for the method of light-cone QCD sum rules. The emphasis is on the vector mesons and a new (model-independent) way of computing the mass corrections of vector-meson wave functions is given.
The different light-cone wave functions of the photon up to twist four are defined. Some explicit expressions are extracted from results of Balitskii and al., Ali and Braun.
We suggest to use operator product expansion and QCD sum rule techniques to estimate the long-distance contribution to the amplitude of the exclusive rare decay $B\to K^* γ$. In contrast to a phenomenological description in terms of $ψ$ resonances converting into a photon, the virtual charm quark loop interacting with soft gluons is represented by a new quark-gluon-photon operator. The matrix element of this operator is calculated in the same approximation as the matrix element of the leading magnetic penguin operator. The overall correction is found to be small, not more than about 5%.
We calculate the contribution of the weak annihilation to the $B\rightarrow ργ$ decay amplitude by means of QCD sum rules using the photon light-cone wave function. We find that this long-distance contribution amounts to about 10\% of the leading short-distance effect in $B^-\rightarrow ρ^-γ$. On the other hand, weak annihilation is the dominant source of the corresponding $D$ meson decays and according to our estimates, yields branching ratios of $O(10^{-4})$ for $D^0\rightarrow \bar{K}^{*0}γ$, $O(10^{-5})$ for $D_s\rightarrow ρ^+γ$, and $O(10^{-6})$ for $D^-\rightarrow ρ^-γ$ and for $D^0\rightarrow ρ^0γ$.