Alexander Khodjamirian

QCD sum rules, a modern perspective

An introduction to the method of QCD sum rules is given for those who want to learn how to use this method. Furthermore, we discuss various applications of sum rules, from the determination of quark masses to the calculation of hadronic form factors and structure functions. Finally, we explain the idea of the light-cone sum rules and outline the recent development of this approach.

Decay constants of heavy-light vector mesons from QCD sum rules

We revisit QCD sum rules for the decay constants of heavy-light mesons. In the sum rules for the vector mesons B^*_(s) and D^*_(s) we improve the accuracy of OPE, taking into account the O(alpha_s^2) terms in the perturbative part and calculating the O(alpha_s) corrections to the quark-condensate contribution. With this accuracy, we obtain the ratios of decay constants: f_B^*/f_B=1.02 +0.07 -0.03, f_D^*/f_D=1.20 +0.10 -0.07. The sum rule predictions for the decay constants of pseudoscalar mesons are updated with the results f_B=(207 +17 -9) MeV, f_B_s=(242 +17 -12) MeV, f_D=(201 +12 -13) MeV, f_D_s=(238 +13 -23) MeV. In order to assess the sensitivity of our calculation to the form of the sum rule, we consider alternative versions such as the power moments and Borel sum rules with different weights of the spectral density. We also investigated the heavy quark limit of the sum rules for vector and pseudoscalar mesons, estimating the violations of the heavy-quark spin and flavour symmetry.

Form factors of

The method of light-cone QCD sum rules is applied to the calculation of the form factors of

\gamma^*\rho\to\pi

\gamma^*\rho \to \pi

and

and

\gamma^*\gamma\to\pi^0

\gamma^*\gamma \to \pi^0

transitions and light-cone sum rules

transitions. We consider the dispersion relation for the

Exploring light-cone sum rules for pion and kaon form factors

\gamma^*(Q^2)\gamma^*(q^2) \to \pi^0

Flavor SU(3) symmetry in charmless B decays

amplitude in the variable

Disentangling the Decay Observables in

q^2