Conceptual problems of unified two-nucleon force models are discussed. The force models are based on the pion-nucleon vertex and attempt a description of the nucleon-nucleon interaction below and above pion threshold. The conceptual problems arise from the nucleon renormalization due to pionic degress of freedom. Keeping channels with a single pion only no renormalization procedure can be given...

We explore the relationship between exclusive and inclusive electromagnetic scattering from the pion, focusing on the transition region at intermediate Q2. Combining Drell-Yan data on the leading twist quark distribution in the pion with a model for the resonance region at large x, we calculate QCD moments of the pion structure function over a range of Q2, and quantify the role of higher twist ...

We test the positivity property of the chiral perturbation theory (ChPT) pion-pion scattering amplitudes within the Mandelstam triangle. In the one-loop approximation, O(p4), the positivity constrains only the coefficients b3 and b4, namely one obtains that b4 and the linear combination b3 + 3b4 are positive quantities. The two-loops approximation gives inequalities involving all the six arbitr...

We evaluate the vector and scalar form factor of the pion in the presence of virtual photons at next–to–leading order in two–flavor chiral perturbation theory. We also consider the scalar and tensor pion form factors of the energy–momentum tensor. We find that the intrinsic electromagnetic corrections are very small for the vector and charged pion scalar form factor. The scalar radius of the ne...

Independent of assumptions about the form of the quark-antiquark scattering kernel we derive the explicit relation between the pion Bethe-Salpeter amplitude, Γπ, and the quark propagator in the chiral limit; Γπ necessarily involves a non-negligible γ5γ · P term (P is the pion four-momentum). We also obtain exact expressions for the pion decay constant, fπ, and mass, both of which depend on Γπ; ...

The availaible data on the D0 → K0 S π+π− decays are analysed in the framework of the quasi two-body QCD factorization approximation. The annihilation, via Wexchange, amplitudes are added to the weak-decay tree amplitudes. The doubly Cabibbo suppressed parts of the amplitudes are also considered. The strong interactions between the kaon-pion and pion-pion pairs in the S -, Pand D-final states a...

We compute the matrix elements for pion emission from the nucleon induced by twist-two light-cone operators in the kinematics where the pion is close to threshold. It is shown that the results of heavy baryon ChPT are in agreement with the results from the soft-pion theorem approach. Therefore the amplitude of soft-pion emission is directly related to the generalized parton distributions in the...

We present a model for the structure of the pion. Based on ideas of a recently developed statistical model of the nucleon, we assume the pion to be a gas of partons. The finite-size corrections (FSC) are incorporated through two parameters. Using the same two FSC parameters for the proton and pion we reproduce quantitatively the data on πN → μ+μ−X Drell-Yan production and valence quark distribu...

Objective: The electric (ᾱ) and magnetic (β̄) pion Compton polarizabilities characterize the pion’s deformation in the electromagnetic field of the γ during γπ Compton scattering. They depend on the rigidity of the pion’s internal structure as a composite particle. The polarizabilities deduced by Antipov et al. in their low statistics Primakoff experiment (∼ 7000 events) were ᾱπ = −β̄π = 6.8± 1.4...

∫ dk⊥Ψπ(x,~k⊥)k 2 ⊥ = 〈~k 2 ⊥〉 = −M〈ūu〉/f 2 π for the second moment of the pion light-cone wave function, where M is the constituent quark mass and fπ is the pion decay constant. After the QCD Gegenbauer evolution of the pion distribution amplitude good end-point behavior is recovered, and a satisfactory agreement with the analysis of the experimental data from CLEO is achieved. This allows us ...