Related papers: F2c at low x
We compare the results of the fixed-flavor scheme calculation of Laenen, Riemersma, Smith and van Neerven with the variable-flavor scheme calculation of Aivazis, Collins, Olness and Tung for neutral-current (photon-mediated) heavy-flavor…
New results on charm quark production at HERA in an increased phase space in deep-inelastic scattering and photoproduction are discussed. Single & double-differential cross section distributions are compared to next-to-leading order QCD…
We investigate the evolution of parton densities at small values of the momentum fraction, x, by including resummed anomalous dimensions in the renormalization group equations. The resummation takes into account the leading-logarithmic…
We present a method for the analytic solution of small $x$ structure functions. The essential small $x$ logarithms are summed to all orders in the anomalous dimensions and coefficient functions. Although we work at leading logarithmic…
We accomplish for the first time the next-to-leading-order QCD computations of the leading-twist contributions to the Dirac form factors of both the proton and the neutron by applying the hard-collinear factorization theorem rigorously. The…
We study inclusive electroproduction on the proton at low $x$ and low $Q^2$ using a soft and a hard Pomeron. The contribution of the soft Pomeron is based on the Stochastic Vacuum Model, in which a nonperturbative dipole-dipole cross…
We check the impact of the gluon distribution due to the number of active flavor employed in the calculation of heavy-quark deep-inelastic scattering (DIS) electro-production on the reduced cross section and structure functions determined…
We have completed the next-to-leading order perturbative QCD corrections to the virtual-photon exclusive differential cross sections for heavy quark production in deep-inelastic electron-proton scattering, i.e. $e + P \rightarrow Q +…
The numerical study of QED radiative corrections in the low x region for the H1 experiment at HERA was performed. The analytical program TERAD91 was used to obtain the values of the radiative correction factor for the first measurement of…
The structure function of the proton has been investigated and has been found to possess the power law behaviour in conformity with the empirical fits to the experimental findings. We have estimated F$_{2}$(x, Q$^{2}$)/F$_{2}$(x,…
Electroproduction in deep inelastic scattering at HERA is studied in a model considering a finite sum of gluon ladders, associated with a truncation of the BFKL series. The approach contains the bare two gluon exchange and both one and two…
We consider heavy quark mass ($m$) effects in the Energy-Energy Correlation function in $e^+e^- \to hadrons$ at high energy $Q$, in the back-to-back (two-jet) region. In the ultra-relativistic limit, $Q \gg m$, the QCD Sudakov form factor…
We illustrate geometric scaling for the photon-proton cross section with a very simple saturation model. We describe the proton structure function F2 at small x in a wide kinematical range with an elementary functional form and a small…
We present a QCD analysis of the proton structure function $F_2$ measured by the H1 experiment at HERA, combined with data from previous fixed target experiments. The gluon density is extracted from the scaling violations of $F_2$ in the…
We compute the imaginary part of the heavy quark contribution to the photon polarization tensor, i.e. the quarkonium spectral function in the vector channel, at next-to-leading order in thermal QCD. Matching our result, which is valid…
During the last year, analytic expressions for the two-loop QCD corrections to the form factors for the vector, axial-vector, scalar and pseudo-scalar vertices involving a pair of heavy quarks, $Q \bar{Q}$, were calculated. The results are…
We report on the extension of the data fitting considering the QCD inspired model based on the summation of gluon ladders applied to the $ep$ scattering. In lines of a two Pomeron approach, the structure function $F_2$ has a hard piece…
Higher twist corrections to the structure function F_2 at small x are studied for the case of a flat initial condition for the twist-two QCD evolution in the next-to-leading order approximation. We present an analytical parameterization of…
We describe a next-to-leading-order calculation of the fully exclusive parton cross section for the photoproduction of heavy quarks. We use our result to compute quantities of interest for current fixed-target experiments. We discuss…
We review small $x$ contributions to perturbative evolution equations for parton distributions, and their resummation. We emphasize in particular the resummation technique recently developed in order to deal with the apparent instability of…