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A. V. Lipatov

Publications and source records attributed to A. V. Lipatov.

At least 91 records · Page 5Linked to original sources
arXiv2011

Prompt J/Psi production at LHC: new evidence for the kt-factorization

In the framework of the kt-factorization approach, the production and polarization of prompt J/Psi mesons in pp collisions at the LHC energy 7 TeV is studied. Both the direct production mechanism as well as feed-down contributions from chic1, chic2 and psi' decays are taken into account. Our consideration is based on the color singlet model supplemented with the off-shell matrix elements for the corresponding partonic subprocesses. The unintegrated gluon densities in a proton are determined using the CCFM evolution equation as well the Kimber-Martin-Ryskin prescription. We compare our numerical predictions with the first experimental data taken by the CMS, ATLAS and LHCb collaborations. The estimation of all polarization parameters which determine J/Psi spin density matrix is performed.

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arXiv2011

Phenomenology of kt-factorization for inclusive top quark pair production at hadron colliders

We investigate the inclusive top quark pair production in proton-proton and proton-antiproton collisions at high energies in the framework of kt-factorization QCD approach. Our study is based on the off-shell partonic subprocesses g*g* -> QQ and q*q* -> QQ, where the transverse momentum of both incoming quarks and gluons are taken into account. The unintegrated parton densities in a proton are determined by the Kimber-Martin-Ryskin prescription as well as the CCFM evolution equation. The conservative error analisys is performed and comparison with the results of traditional NLO pQCD calculations is done. Our predictions agree well with the recent experimental data taken by the D0, CDF, CMS and ATLAS collaborations at the Tevatron and LHC energies.

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arXiv2011

Open b production at LHC and Parton Shower Effects

We present hadron-level predictions from the Monte Carlo generator Cascade and numerical level calculations of beauty quark and inclusive b-jet production in the framework of the kT -factorization QCD approach for CERN LHC energies. The unintegrated gluon densities in a proton are determined using the CCFM evolution equation and the Kimber- Martin-Ryskin (KMR) prescription. We study the theoretical uncertainties of our calcula- tions and investigate the effects coming from parton showers in initial and final states. Our predictions are compared with the recent data taken by the CMS collaboration.

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arXiv2011

Testing for kt-factorization with inclusive prompt photon production at LHC

We study the possibility to analyse the data on inclusive prompt photon production at first LHC runs in the framework of the kt-factorization QCD approach. Our consideration is based on the amplitude for the production of a single photon associated with a quark pair in the fusion of two off-shell gluons. The quark component is taken into account separately using the quark-gluon Compton scatterring and quark-antiquark annihilation QCD subprocesses. The unintegrated parton densities in a proton are determined using the Kimber-Martin-Ryskin (KMR) prescription as well as the CCFM evolution equation.

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arXiv2010

Inclusive J/Psi photoproduction and polarization at HERA in the kt-factorization approach

We investigate the inclusive photoproduction of J/Psi mesons at HERA within the framework of the kt-factorization QCD approach. Our consideration is based on the color singlet model supplemented with the relevant off-shell matrix elements and the CCFM and KMR unintegrated gluon densities in a proton and in a photon. Both the direct and resolved photon contributions are taken into account. Our predictions are compared with the recent experimental data taken by the H1 and ZEUS collaborations. Special attention is put on the J/Psi polarization parameters lambda and nu which are sensitive to the production dynamics.

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arXiv2010

Heavy Flavour Production at Tevatron and Parton Shower Effects

We present hadron-level predictions from the Monte Carlo generator Cascade and numerical calculations of charm and beauty production at the Fermilab Tevatron within the framework of the $k_T$-factorization QCD approach. Our consideration is based on the CCFM-evolved unintegrated gluon densities in a proton. The performed analysis covers the total and differential cross sections of open charm and beauty quarks, $B$ and $D$ mesons (or rather muons from their semileptonic decays) and the total and differential cross sections of $b \bar b$ di-jet hadroproduction. We study the theoretical uncertainties of our calculations and investigate the effects coming from parton showers in initial and final states. Our predictions are compared with the recent experimental data taken by the D0 and CDF collaborations. Special attention is put on the specific angular correlations between the final-state particles. We demonstrate that the final state parton shower plays a crucial role in the description of such observables. The decorrelated part of angular separations can be fully described, if the process $gg^*\rightarrow gg$ is included.

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arXiv2010

Study of non-collinear parton dynamics in the prompt photon photoproduction at HERA

We investigate the prompt photon photoproduction at HERA within the framework of kt-factorization QCD approach. Our consideration is based on the off-shell matrix elements for the underlying partonic subprocesses. The unintegrated parton densities in a proton and in a photon are determined using the Kimber-Martin-Ryskin (KMR) prescription. Additionally, we use the CCFM-evolved unintegrated gluon as well as valence and sea quark distributions in a proton. A conservative error analisys is performed. Both inclusive and associated with the hadronic jet production rates are investigated. The theoretical results are compared with the recent experimental data taken by the H1 and ZEUS collaborations. We study also the specific kinematical properties of the photon-jet system which are strongly sensitive to the transverse momentum of incoming partons. Using the KMR scheme, the contribution from the quarks emerging from the earlier steps of the parton evolution is estimated and found to be of 15 - 20 approximately.

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arXiv2010

On the quark component in prompt photon and electroweak gauge boson production at high energies

In the framework of the kt-factorization approach, we study the production of prompt photons and electroweak gauge bosons in high energy proton-(anti)proton collisions at modern colliders. Our consideration is based on the amplitude for the production of a single photon or W/Z boson associated with a quark pair in the fusion of two off-shell gluons. The quark component is taken into account separately using the quark-gluon scaterring and quark-antiquark annihilation QCD subprocesses. Special attention is put on the contributions from the quarks involved into the earlier steps of the evolution cascade. Using the Kimber-Martin-Ryskin formalism, we simulate this component and demonstrate that it plays an important role at both the Tevatron and LHC energies. Our theoretical results are compared with recent experimental data taken by the D0 and CDF collaborations at the Tevatron.

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arXiv2010

Deep inelastic prompt photon production at HERA in the kt-factorization approach

We investigate the prompt photon production in deep inelastic scattering at HERA in the framework of kt-factorization QCD approach. Our study is based on the off-shell partonic amplitude e q* -> e gamma q, where the photon radiation from the leptons as well as from the quarks is taken into account. The unintegrated quark densities in a proton are determined using the Kimber-Martin-Ryskin prescription. The conservative error analisys is performed. We investigate both inclusive and jet associated prompt photon production rates. Our predictions are compared with the recent experimental data taken by the H1 and ZEUS collaborations. We demonstrate that in the kt-factorization approach the contribution from the quark radiation subprocess (QQ mechanism) is enhanced as compared to the leading-order collinear approximation.

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arXiv2009

Associated production of Higgs boson and heavy quarks at the LHC: predictions with the kt-factorization

In the framework of the kt-factorization approach, we study the production of Higgs bosons associated with a heavy (beauty or top) quark pair at the CERN LHC collider conditions. Our consideration is based mainly on the off-shell gluon-gluon fusion suprocess g + g -> Q + Q + H. The corresponding matrix element squared have been calculated for the first time. We investigate the total and differential cross sections of bbH and ttH production taking into account also the non-negligible contribution from the q + q -> Q + Q + H mechanism. In the numerical calculations we use the unintegrated gluon distributions obtained from the CCFM evolution equation. Our results are compared with the leading and next-to-leading order predictions of the collinear factorization of QCD.

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arXiv2008

Prompt photon hadroproduction in the k_T-factorization approach

We study the production of prompt photons at high energy in the framework of the k_T-factorization approach. The amplitude for production of a single photon associated with quark pair in the fusion of two off-shell gluons is calculated. Theoretical results are compared with the Tevatron data.

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arXiv2008

Production of electroweak gauge bosons in off-shell gluon-gluon fusion

We study the production of electroweak gauge bosons at high energies in the framework of kt-factorization QCD approach. Contributions from the valence quarks are calculated using the quark-gluon interaction and quark-antiquark annihilation QCD subprocesses. The total and differential cross sections (as a function of the transverse momentum and rapidity) are presented and the ratio of cross sections for W and Z boson production is investigated. The conservative error analysis is performed. In the numerical calculations two different sets of unintegrated gluon distributions in the proton are used: the one obtained from Ciafaloni-Catani-Fiorani-Marchesini evolution equation and the other from Kimber-Martin-Ryskin prescription. Theoretical results are compared with experimental data taken by the D0 and CDF collaborations at the Tevatron. We demonstrate the importance of the quark component in parton evolution in description of the experimental data. This component is very significant also at the LHC energies.

hep-ph↗
arXiv2008

Associated production of prompt photons and heavy quarks in off-shell gluon-gluon fusion

In the framework of the kt-factorization approach, we study the production of prompt photons associated with heavy (charm and beauty) quarks in hadron-hadron collisions at high energies. Our consideration is based on the amplitude for the production of a single photon associated with a quark pair in the fusion of two off-shell gluons. The total and differential cross sections are presented and the conservative error analysis is performed. Two sets of unintegrated gluon distributions in the proton have been used in numerical calculation: the one obtained from Ciafaloni-Catani-Fiorani-Marchesini evolution equation and the other from Kimber-Martin-Ryskin prescription. The theoretical results are compared with recent experimental data taken by the CDF collaboration at the Fermilab Tevatron. Our analysis extends to specific angular correlations between the produced prompt photons and muons originating from semileptonic decays of the final charmed or beauty quarks. We point out the importance of such observables, which can serve as a crucial test for the unintegrated gluon densities in a proton. Finally, we extrapolate the theoretical predictions to the CERN LHC energies. This paper is dedicated to the memory of P.F. Ermolov, who died on May 14, 2008.

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arXiv2008

Prompt photon hadroproduction at high energies in off-shell gluon-gluon fusion

The amplitude for production of a single photon associated with quark pair in the fusion of two off-shell gluons is calculated. The matrix element found is applied to the inclusive prompt photon hadroproduction at high energies in the framework of kt-factorization QCD approach. The total and differential cross sections are calculated in both central and forward pseudo-rapidity regions. The conservative error analisys is performed. We used the unintegrated gluon distributions in a proton which were obtained from the full CCFM evolution equation as well as from the Kimber-Martin-Ryskin prescription. Theoretical results were compared with recent experimental data taken by the D0 and CDF collaborations at Fermilab Tevatron. Theoretical predictions for the LHC energies are given.

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arXiv2007

Beauty production in two-photon interactions at LEP2: kt-factorization versus data

Inclusive beauty quark production in photon-photon collisions at CERN LEP2 is considered in the framework of the kt-factorization approach. Both direct and resolved photon contributions are taken into account. The unintegrated gluon distributions in a photon are either obtained from the full CCFM evolution equation or from the Kimber-Martin-Ryskin prescription. The predicted beauty cross section reasonably agrees with the recent experimental data taken by the ALEPH collaboration. We argue that theoretical and experimental studies of the azimuthal correlations in heavy quark production at high energies can serve as a crucial probe of the unintegrated gluon densities.

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arXiv2007

Critical tests of unintegrated gluon distributions

We use the unintegrated Parton Density Functions of the gluon obtained from a fit to measurements of the structure functions F2 and F2c at HERA to describe the experimental data for F2b, FL and FL at fixed W.

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arXiv2007

Heavy Quarks: Summary Report

The present status of the heavy-quark production theory is critically reviewed in the first contribution. The second contribution summarises the present heavy flavour data from HERA and gives an outlook of what can be expected from HERA-II. The potential of the LHC experiments for charm and beauty physics is reviewed in the 3rd contribution. Then the relevance of saturation and small-x effects to heavy quark production at HERA and at the LHC are discussed. The non-perturbative aspects of heavy-quark fragmentation and their relevance to HERA and LHC are discussed in the next contribution. Finally, a comparison of different theoretical predictions for HERA and LHC based on different approaches is presented.

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