Models for hadronic and leptonic processes at high energy

Proton structure function at smallQ 2

“…According to the parton model, the same Regge powers appear [9] as powers of 1/x in the small-x behaviour of νW 2 . The parton model is drawn in figure 2, where the amplitude T is the amplitude for the emission of a parton of momentum k by the proton.…”

“…The parton model is drawn in figure 2, where the amplitude T is the amplitude for the emission of a parton of momentum k by the proton. From simple kinematics [9] , the energy variable for this amplitude is…”

“…To derive such slow rescaling one would need two assumptions: (i) that the mass scale associated with the fragmentation of the charmed quark after it has absorbed the virtual photon is m c rather than that of the lightest hadron to which it can fragment; and (ii) one can ignore the fact that the momentum k of the quark before it absorbs the photon is not on shell. The fact that µ c needs to be so large indicates that neither of these assumptions is tenable [9] : not only is the minimum mass of the hadron to which the quark fragments important, so also is the minimum mass of the residual fragments of the proton left behind when the quark has been pulled out of it. The only way that such a mass can be supported is for the quark momentum k to go off shell and become negative: see (3).…”

Generalized Parton Distributions: Visions, Basics, and Realities

“…Since parton diagonal overlap representations can be naturally converted in the form of DD representations, one can utilize GPD-duality to calculate the full GPD from the parton diagonal LFWF overlap, however, only for the case that the LFWF respects the underlying Lorentz symmetry [73; 96; 97]. Note also that 'Regge' behavior can be implemented in such simple models from the s-channel view [98], however, the problem to implement a t-dependent 'Regge'-trajectory in such a manner that positivity holds true by construction is not solved yet.…”

Model independent analysis of gluonic pole matrix elements and universality of transverse-momentum-dependent fragmentation functions

“…These represent scattering amplitudes and their analytic structure enables one to make statements about the support of the associated parton correlation functions. This can be done for quark-quark [27] and multi-parton correlators [28] and for TMD as well as collinear correlators [29]. In this language the diagrams of Figs.…”