Distribution amplitudes of light mesons and the photon in the instanton model

Abstract

The leading-and higher-twist distribution amplitudes of the pion, the ρ-meson and real and virtual photons are analyzed in the instanton liquid model.

Rho Meson Distribution Amplitudes from QCD Sum Rules with Nonlocal Condensates

“…Their determination within the framework of QCD SRs with nonlocal condensates (NLC) was considered later in [9; 10; 11]. Besides, the ρ-meson DAs were studied in other nonperturbative approaches as well, e.g., lattice QCD [12], AdS/QCD holography [13; 14; 2; 3], the light-front quark model [15], and the instanton liquid model [16]. In this note we improve the previous works in [9; 10; 11] on the ρ-meson longitudinal and transverse DAs in the following respects: (i) we use a corrected expression for the NLO spectral density in the SR for the ρ L DA, (ii) we express the ρ L DA in terms of Gegenbauer coefficients, and (iii) we calculate and use the correct nonperturbative term for the theoretical part of the SR for the ρ T DA.…”

ρ-meson longitudinal leading-twist distribution amplitude within QCD background field theory

“…By using the relations among the Gegenbauer moments a n;ρ and the moments ξ n;ρ , such as Eqs. (16,17,18), we can derive a n;ρ at the scale M . Furthermore, the Gegenbauer moments a n;ρ at any other scale can be obtained via the QCD evolution, i.e.…”

“…The first two Gegenbauer moments a 2;ρ and a 4;ρ for the longitudinal leading-twist DA φ 2;ρ , which is predicted from the sum rules under the BFT. A comparison of predictions under various approaches [9][10][11][12][13][14][15][16] has also been presented. For easy comparison, we have set the scale µ0 = 1GeV.…”

“…We adopt the present DA moments to fix a ρ-meson wavefunction ψ 2;ρ (x, k ⊥ ) that is constructed from the Wu-Huang (WH) model [56] predicted from the sum rules under the BFT (BFTSR). As a comparison, the NLCSR prediction [9], the BB prediction [10], the Lattice QCD prediction [11], the AdS/QCD prediction [13,14], the LFQM prediction [15], and the IM prediction [16] have also been presented. whose radial part is from the BHL-prescription [57].…”

“…Gegenbauer moments have been studied via various approaches [8][9][10][11][12][13][14][15][16]. Most of their predictions are consistent with each other, but are of large theoretical uncertainties.…”