Pion form factor in thekTfactorization formalism

Abstract

Based on the light-cone (LC) framework and the k T factorization formalism, the transverse momentum effects and the different helicity components' contributions to the pion form factor F Q 2 are recalculated. In particular, the contributions to the pion form factor from the higherhelicity components ( 1 2 1), which come from the spin-space Wigner rotation, are analyzed in the soft and hard energy regions, respectively. Our numerical results show that the right power behavior of the hard contribution from the higher-helicity components can only be obtained by fully keeping the k T dependence in the hard amplitude, and that the k T dependence in LC wave function affects the hard and soft contributions substantially. As an example, we employ a model LC wave function to calculate the pion form factor and then compare the numerical predictions with the experimental data.

Heavy pseudoscalar leading-twist distribution amplitudes within QCD theory in background fields

“…By adopting the conventional correlator for the LCSRs, similar to the B → π TFFs [31], the TFF f B c →η c + (q 2 ) shall be formulated as the function involving the η c leading-twist DA, twist-3 DA, and other higher-twist DAs. The higher-twist DAs follow the power suppression rule in large scale region; however, they may have sizable contributions to the TFF in the intermediate energy regions, similar to the pionic cases of the B → π TFFs and the pion TFFs [32,33]. At present, the η c highertwist DAs are still with great uncertainty, thus the possible LCSRs with η c various twist DAs shall inversely greatly dilute our understanding of the leading-twist DA behaviors.…”

$$\gamma \gamma \rightarrow M^{+}M^{-}(M=\pi , K)$$ γ γ → M + M - ( M = π , K ) processes with twist-3 corrections in QCD

“…However, the Fourier transform of the hardscattering amplitude becomes difficult in this situation. For an estimate of the twist-3 effect, we use the Brodsky-HuangLepage (BHL) prescription for the harmonic-oscillator wave function (WF) [28][29][30][31] in this paper, since the BHL DAs have a better endpoint behavior in the soft regions. Our results also indicate that the twist-3 distribution amplitudes of the pion and kaon make significant contributions at the energy region W ∈ (1, 6) GeV.…”

Electromagnetic structure of pion

“…In it, the light-front formalism is applied to the electromagnetic form factor, calculated with the + components of the currents of the quark-antiquark bound states of the pion. Methods based on the lightfront formalism have been successful in the description of the electromagnetic properties of the hadronic wave functions [17,18,19,20,21,22,23,24,25].…”