the proton in the rest frame of the proton is given by $y = P \cdot q / P \cdot k$. At HERA energies, the masses of the incoming electrons (protons) with energies $E_e$ ($E_p$) can be neglected and the variables $Q^2$, $x_{\rm{Bj}}$ and $y$ are related as $Q^2=sx_{\rm{Bj}}y$, where $s=4E_eE_p$ is the square of the electron–proton centre-of-mass energy. The components of the Standard Model necessary to describe the data are the electroweak (EW) theory and perturbative Quantum Chromo Dynamics (pQCD). At leading order, the EW theory supplies the cross sections for electron scattering from partons with electric charge, i.e. the quarks. The EW theory is subject to pQCD corrections, which already at next-to-leading order make the electron scattering sensitive to the gluons in the proton. The dynamics of the partons, quarks and gluons, are described via their PDFs. The PDFs provide the probability of finding a given parton with a momentum fraction $x$ for an interaction at a given factorisation scale, $\mu_{\rm f}$, which is usually chosen to be $Q^2$. In pQCD, the PDFs evolve with $Q^2$ depending on the order of the strong coupling constant, $\alpha_s$, at which the perturbative series is truncated. The analysis presented in this 