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Register a new userThe Structure Functions F_2^c, F_L and F_L^c in the Framework of the k_T Factorization
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We present the perturbative parts of the structure functions F_2^c and F_L^c for a gluon target having nonzero transverse momentum squared at order alpha _s. The results of the double convolution (with respect to the Bjorken variable x and the transverse momentum) of the perturbative part and the unintegrated gluon densities are compared with HERA experimental data for F_2^c and F_L at low x values and with predictions of other approaches. The contribution from F_L^c structure function ranges 10div30% of that of F_2^c at the HERA kinematical range.
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We calculate the perturbative parts of the structure functions $F_2^c$ and $F_L^c$ for a gluon target having nonzero transverse momentum squared at order $alpha_s$. The results of the double convolution (with respect to the Bjorken variable $x_B$ and the transverse momentum) of the perturbative part and the unintegrated gluon densities are compared with HERA experimental data for $F_2^c$. The contribution from $F_L^c$ structure function ranges (10-30)% of that of $F_2^c$ at the kinematical range of HERA experiments.
We use results for the structure functions $F_L$ for a gluon target having nonzero transverse momentum square at order $alpha_s$, obtained in our previous paper, to compare with recent H1 experimental data for $F_L$ at fixwd W values and with collinear GRV predictions at LO and NLO approximation.
A novel factorization formula is presented for the longitudinal structure function $F_L$ near the elastic region $x to 1$ of deeply inelastic scattering. In moment space this formula can resum all contributions to $F_L$ that are of order $ln^k N/N$. This is achieved by defining a new jet function which probes the transverse momentum of the struck parton in the target at leading twist. The anomalous dimension $gamma_{J^prime}$ of this new jet operator generates in moment space the logarithmic enhancements coming from the fragmentation of the current jet in the final state. It is also shown how the suggested factorization for $F_L$ is related to the corresponding one for $F_2$ in the same kinematic region.
We present a new approach for the prompt production of quarkonia which is based on the $k_T$-factorization method. The production of even C-parity quarkonia proceeds via the fusion of two (off-shell) gluons. Especially in the kinematics of the LHCb experiment these processes are thus expected to be a sensitive probe of the small-$x$ gluon distribution. We calculate the relevant off-shell matrix elements in terms of the light-front wave functions of the quarkonium states. We present our results for scalar and pseudoscalar charmonia and discuss photon transition form factors as well as cross sections for prompt hadroproduction. We compare our results for the $eta_c$ to recent LHCb data.
We make predictions for the diffractive longitudinal structure function F_L^D to be measured at HERA, based on DGLAP fits of diffractive parton distributions with twist--4 contribution. This contribution describes diffractive qqbar production from longitudinal photons and significantly changes predictions for F_L^D obtained in pure DGLAP analyses.
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