Possible saturation effects at HERA and LHC in the kTk_T-factorization approach

We consider possible saturation effects in the structure function $F_L$ at fixed W in HERA energy range and in $b\bar b-$production at LHC energies in the framework of $k_T-$facrorization approach.Comment: 5 pages, 3 figures, prepared for the Proceedings of XXXV International Symposium on Multipaticle Dynamics 2005, Kromeriz, Czech Republic, Aug. 9-15, 200

TMD parton densities in associated real and virtual photon and jet production at LHC

We study the associated production of real (isolated) or virtual photons (with their subsequent leptonic decay) and hadronic jets in proton-proton collisions at the LHC using the $k_T$-factorization approach of QCD. The consideration is based on the off-shell quark-gluon QCD Compton scattering subprocesses. In the case of virtual photon production, the contributions from Z boson exchange as well as gamma*-Z interference with the full spin correlations are included. The transverse momentum dependent (TMD) quark and gluon densities in a proton are determined from the Kimber-Martin-Ryskin prescription or Catani-Ciafoloni-Fiorani-Marchesini (CCFM) equation. In the latter, we restricted to the case where the gluon-to-quark splitting occurs at the last evolution step and calculate the sea quark density as a convolution of the CCFM-evolved gluon distribution and the TMD gluon-to-quark splitting function. Our numerical predictions are compared with the recent experimental data taken by the ATLAS Collaboration. We discuss the theoretical uncertainties of our calculations and argue that further studies are capable of constraining the TMD parton densities in a proton.Comment: 11 pages, 4 figures. arXiv admin note: text overlap with arXiv:1402.549

On the possibility to detect the Higgs decay H→bbˉH\to b\bar b in the associated Z+bbˉZ + b\bar b production at the LHC

We investigate the possibility to detect the scalar Higgs boson decay $H\to b\bar b$ in the associated $Z$ and $b\bar b$ production at the LHC using the $k_T$-factorization QCD approach. Our consideration is based on the off-shell (i.e. depending on the transverse momenta of initial quarks and gluons) production amplitudes of $q^* \bar q^* \to Z H \to Z q^\prime \bar q^\prime$, $q^* \bar q^* \to Z q^\prime \bar q^\prime$ and $g^* g^* \to Z q^\prime \bar q^\prime$ partonic subprocesses supplemented with the Catani-Ciafoloni-Fiorani-Marchesini (CCFM) dynamics of parton densities in a proton. We argue that the $H \to b\bar b$ signal could be observed at large transverse momenta near Higgs boson peak despite the overwhelming QCD background, and point out an important role of angular correlations between the produced $Z$ boson and $b$-quarks.Comment: 11 pages, 6 figure

The contribution of off-shell gluons to the longitudinal structure function F_L

We present results for the structure function F_L for a gluon target having nonzero transverse momentum square at order \alpha_s. The results of double convolution (with respect to Bjorken variable x and the transverse momentum) of the perturbative part and the unintegrated gluon densities are compared with recent experimental data for F_L at low x values and with predictions of other approaches.Comment: 21 pages, 4 figures, late