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Description
A phenomenological study of the final combined HERA data on inclusive deep inelastic scattering (DIS) has been performed. The data are presented and investigated for a kinematic range extending from values of the four-momentum transfer, $Q^2$, above 10$^4$ GeV$^2$ down to the lowest values observable at HERA of $Q^2$ = 0.045 GeV$^2$ and Bjorken x, $x_{Bj}$ = 6 x 10−7. The data are well described by fits based on perturbative quantum chromodynamics (QCD) using collinear factorisation and evolution of the parton densities encompassed in the DGLAP formalism from the highest $Q^2$ down to $Q^2$ of a few GeV$^2$. The standard DGLAP evolution was augmented by including an additional higher-twist term in the description of the longitudinal structure function, $F_L$. This additional term, $F_L A_L^{HT}/Q^2$, improves the description of the reduced cross sections significantly. The resulting predictions for $F_L$ suggest that further corrections are required for Q^2 less than about 2 GeV^2. The Regge formalism can describe the data up to $Q^2$ ~ 0.65 GeV$^2$. The complete data set can be described by a new fit using the ALLM parameterisation. The region between the Regge and the perturbative QCD regimes is of particular interest.
Covers 2 papers:
I. Abt et al., Phys. Rev. D 94 (2016) 034032, arXiv:1604.02299
I. Abt et al., arXiv:170403187
