Terms Of Light-cone Wave Functions Research Articles

Transverse-momentum distributions in a diquark spectator model

All the leading-twist parton distribution functions are calculated in a spectator model of the nucleon, using scalar and axial-vector diquarks. Single gluon rescattering is used to generate $T$-odd distribution functions. Different choices for the diquark polarization states are considered, as well as a few options for the form factor at the nucleon-quark-diquark vertex. The results are listed in analytic form and interpreted in terms of light-cone wave functions. The model parameters are fixed by reproducing the phenomenological parametrization of unpolarized and helicity parton distributions at the lowest available scale. Predictions for the other parton densities are given and, whenever possible, compared with available phenomenological parametrizations.

Deeply Virtual Compton Scattering in e- e- and e- γ Collisions

The matrix elements of the local operators such as electromagnetic current, energy momentum tensor, angular momentum, and generalized parton distributions have exact representations in terms of light-cone Fock state wavefunctions of bound states such as hadrons. We present formulae which express the form factors of the local operators in terms of the light-cone wavefunctions. We propose the measurement of the generalized parton distributions of the high energy real photon by the deeply virtual Compton scattering experiments.

Applications of light-cone wavefunctions to QCD phenomena

Abstract The matrix elements of the local operators such as electromagnetic current, energy momentum tensor, angular momentum, and skewed parton distribution functions have exact representations in terms of light-cone Fock state wavefunctions of bound states such as hadrons. We present formulae which express the form factors of the local operators in terms of the light-cone wavefunctions.

QUARK STRUCTURE OF PSEUDOSCALAR MESONS

I review to which extent the properties of pseudoscalar mesons can be understood in terms of the underlying quark (and eventually gluon) structure. Special emphasis is put on the progress in our understanding of η–η′ mixing. Process-independent mixing parameters are defined, and relations between different bases and conventions are studied. Both, the low-energy description in the framework of chiral perturbation theory and the high-energy application in terms of light-cone wave functions for partonic Fock states, are considered. A thorough discussion of theoretical and phenomenological consequences of the mixing approach will be given. Finally, I will discuss mixing with other states (π0, ηc, …).

Form factors of γ * ρ → π and γ * γ → π 0 transitions and light-cone sum rules

The method of light-cone QCD sum rules is applied to the calculation of the form factors of γ * ρ → π and γ * γ → π 0 transitions. We consider the dispersion relation for the γ *(Q 2)γ *(q 2) → π 0 amplitude in the variable q2. At large virtualities q2 and Q2, this amplitude is calculated in terms of light-cone wave functions of the pion. As a next step, the light-cone sum rule for the γ *(Q 2)ρ → π form factor is derived. This sum rule, together with the quark-hadron duality, provides an estimate of the hadronic spectral density in the dispersion relation. Finally, the γ *(Q 2)γ → π 0 form factor is obtained taking the q 2 = 0 limit in this relation. Our predictions are valid at Q 2 ≥ 1 GeV2 and have a correct asymptotic behaviour at large Q2.

Form factors of

The method of light-cone QCD sum rules is applied to the calculation of the form factors of γ * ρ → π and γ * γ → π 0 transitions. We consider the dispersion relation for the γ *(Q 2)γ *(q 2) → π 0 amplitude in the variable q2. At large virtualities q2 and Q2, this amplitude is calculated in terms of light-cone wave functions of the pion. As a next step, the light-cone sum rule for the γ *(Q 2)ρ → π form factor is derived. This sum rule, together with the quark-hadron duality, provides an estimate of the hadronic spectral density in the dispersion relation. Finally, the γ *(Q 2)γ → π 0 form factor is obtained taking the q 2 = 0 limit in this relation. Our predictions are valid at Q 2 ≥ 1 GeV2 and have a correct asymptotic behaviour at large Q2.

Large rapidity gap events in deep inelastic scattering

Large Rapidity Gap Events in Deep Inelastic Scattering are discussed in terms of lightcone wave functions for quarks and gluons inside the photon. It is shown that this approach is consistent with earlier, conventional Feynman diagram calculations. An updated parametrization for the cross section is given and a numerical analysis presented.

Distribution of valence quarks and light-cone QCD sum rules

A method for calculating the pion structure function directly in terms of light-cone wave functions is suggested. Taking twist-2 and twist-4 pion light-cone wave functions into account, it is shown that the QCD sum rule prediction is in agreement with quark distribution obtained from analysis of the Drell-Yan process. Twist-4 quark-gluon light-cone wave functions give a large positive contribution to the pion structure function for x_B<0.2. A new constraint on the twist-2 pion light-cone wave function is obtained. We argue that the leading twist pion wave function \phi_\pi(u) \simeq 1 for u=0.3 with an accuracy of about 20-30%.