Deep inelastic scattering, QCD, and generalized vector dominance

Abstract

We provide a formulation of generalised vector dominance (GVD) for low-x deep-inelastic scattering that explicitly incorporates the γ * → q q transition and a QCD-inspired ansatz for the (q q)p forward-scattering amplitude. The destructive interference originally introduced in off-diagonal GVD is recovered in the present formulation and traced back to the generic structure of two-gluon-exchange as incorporated into the notion of colour transparency. Asymptotically, the transverse photoabsorption cross section behaves as (ln Q 2 )/Q 2 , implying a logarithmic violation of scaling for F 2 , while the longitudinal-to-transverse ratio decreases as 1/ ln Q 2 .

Hadronic γZ box corrections in Møller scattering

“…This model combines the electromagnetic structure functions of Cvetic et al [35,36] with the constrained γZ/γγ ratio in Eq. (6), as in the AJM model.…”

“…(6), as in the AJM model. Note that for both the CDP and CDP/VMD models the parametrisation [35,36] of the structure functions is given only for W 2 < 1000 GeV 2 . As shown in Fig.…”

Color dipole picture at low- x DIS: The mass range of active photon fluctuations

“…In the CDP, we are exclusively dealing with the q 2 → ∞ limit, and accordingly we replace the approximate equalities in This expression for the qq mass squared enters (1.1) and (1.2) and all the subsequent considerations; M 2 qq denotes the square of the qq mass in the γ * → qq transition to a qq state with life time of order 1/∆E. W [7] [16], in no way different from e.g. πp or ρ 0 p interaction at asymptotic energies, and it cannot depend on the photon virtuality Q 2 .…”

Color Transparency and Saturation in QCD

“…As in GVD, in the modern approach, the photoabsorption reaction proceeds in two steps, i) the γ * → qq transition and ii) the (qq)-proton interaction, whereby taking into account i) the internal structure of the qq system via the variable 0 ≤ z ≤ 1 that specifies the longitudinal momentum distribution between the quark and the antiquark the photon fluctuates into, compare Fig After Fourier transform to transverse position space, the photoabsorption cross section at low x Q 2 /W 2 < 0.1 takes the form [28,29]…”