We study the pion form factor in a broad range of spacelike momentum transfers within the local-duality version of QCD sum rules. We make use of the recently calculated two-loop double spectral density of the AV A correlator including O(1) and O(αs) terms, which allows us to give predictions for the pion form factor and to study the interplay between the nonperturbative and perturbative contributions to the pion form factor without any reference to the pion distribution amplitude. Our results demonstrate the dominance of the nonperturbative contribution to the form factor up to relatively large values of the momentum transfer: namely, the nonperturbative O(1) term, which provides the 1/Q 4 power correction, gives more than half of the pion form factor in the region Q 2 ≤ 20 GeV 2 .
This paper is devoted to the study of leading twist light cone wave functions of J/Ψ meson. The moments of these wave functions have been calculated within three approaches: potential models, nonrelativistic QCD and QCD sum rules. Using the results obtained within these approaches the models for the light cone wave functions of leading twist have been proposed. Similarly to the wave function of ηc meson the leading twist light cone wave functions of J/Ψ meson have very interesting properties at scales µ > mc: improvement of the accuracy of the model, appearance of relativistic tail and violation of nonrelativistic QCD velocity scaling rules. The last two properties are the properties of true leading twist light cone wave functions of J/Ψ meson.
In this paper we carry out a low-temperature scan of the phase diagram of dense two-color QCD with N f = 2 quarks. The study is conducted using lattice simulation with rooted staggered quarks. At small chemical potential we observe the hadronic phase, where the theory is in a confining state, chiral symmetry is broken, the baryon density is zero and there is no diquark condensate. At the critical point µ = mπ/2 we observe the expected second order transition to Bose-Einstein condensation of scalar diquarks. In this phase the system is still in confinement in conjunction with non-zero baryon density, but the chiral symmetry is restored in the chiral limit. We have also found that in the first two phases the system is well described by chiral perturbation theory. For larger values of the chemical potential the system turns into another phase, where the relevant degrees of freedom are fermions residing inside the Fermi sphere, and the diquark condensation takes place on the Fermi surface. In this phase the system is still in confinement, chiral symmetry is restored and the system is very similar to the quarkyonic state predicted by SU(Nc) theory at large Nc.
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