Soft contribution to the pion form factor from light-cone QCD sum rules

We propose a simple method to calculate the pion form factor at not very large momentum transfers, which combines the technique of the QCD sum rules with the description of the pion in terms of the set of wave functions of increasing twist. This approach allows one to calculate the soft (end point) contribution to the form factor in a largely model-independent way. Our results confirm existing expectations that the soft contribution remains important at least up to the momentum transfers of order 10 GeV2, and suggest that it comes from the region of relatively small transverse separations of order 1 GeV−1

On the heavy quark mass expansion for the operator Qbar gamma_5 Q and the charm content of eta, eta'

Recently in the context of studies of the intrinsic charm content of the nucleon and of the eta' meson two groups have arrived at different results for the 1/m^3 term of the heavy quark expansion for operator $\bar Q\gamma_5Q$ differing by the factor of six. We show that the form of both results violates certain general conditions. Using the expression for the axial anomaly with the finite Pauli-Villars regularization we obtain a new expression for 1/m^3 term of the heavy quark expansion for $\bar Q\gamma_5 Q$. With this new result we obtain an estimate for the constant f_{\eta'}^{(c)}=-2 MeV.Comment: 4 page

Bridge between Abelian and Non-Abelian Fractional Quantum Hall States

We propose a scheme to construct the most prominent Abelian and non-Abelian fractional quantum Hall states from K-component Halperin wave functions. In order to account for a one-component quantum Hall system, these SU(K) colors are distributed over all particles by an appropriate symmetrization. Numerical calculations corroborate the picture that the proposed scheme allows for a unification of both Abelian and non-Abelian trial wave functions in the study of one-component quantum Hall systems.Comment: 4 pages, 2 figures; revised version, published in Phys. Rev. Let