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N. P. Zotov

Publications and source records attributed to N. P. Zotov.

At least 37 records · Page 2Linked to original sources
arXiv2011

Investigation of beauty production and parton shower effects at LHC

We present hadron-level predictions from the Monte Carlo generator Cascade and parton level calculations of open b quark, b-flavored hadron and inclusive b-jet production in the framework of the kt-factorization QCD approach for the LHC energies. The unintegrated gluon densities in a proton are determined using the CCFM evolution equation and the Kimber-Martin-Ryskin (KMR) prescription. Our predictions are compared with the first data taken by the CMS and LHCb collaborations at 7 TeV. We study the theoretical uncertainties of our calculations and investigate the effects coming from parton showers in initial and final states. The special role of initial gluon transverse momenta in description of the data is pointed out.

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arXiv2011

Drell-Yan lepton pair production at high energies in the kt-factorization approach

In the framework of the kt-factorization approach, the production of unpolarized Drell-Yan lepton pair at high energies is studied. The consideration is based on the O(alpha) and $O(alpha alpha_s) off-shell partonic matrix elements with virtual photon and Z boson exchange. The calculations include leptonic decays of Z bosons with full spin correlations as well as gamma - Z interference. The unintegrated parton densities in a proton are determined by the Kimber-Martin-Ryskin prescription. Our numerical predictions are compared with the data taken by the D0, CDF and CMS collaborations at the Tevatron and LHC energies. Special attention is put on the specific angular distributions measured very recently by the CDF collaboration for the first time.

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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.

hep-ph↗
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.

hep-ph↗
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.

hep-ph↗
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.

hep-ph↗
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.

hep-ph↗
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.

hep-ph↗
arXiv2008

Production and polarization of Upsilon mesons in the k_T-factorization approach in more detail

In the framework of the k_T-factorization approach, the production and polarization of Upsilon mesons at the Fermilab Tevatron is considered, and a comparision of the calculated double differential distributions and spin alignment parameter $α$ with the D0 experimental data is shown. We argue that measuring the double differential cross section and the polarization of upsilonium states can serve as a crucial test discriminating two competing theoretical approaches to the parton dynamics in QCD.

hep-ph↗
arXiv2008

Upsilonium Polarization as a Touchstone in Understanding the Parton Dynamics in QCD

In the framework of the $k_T$-factorization approach, the production of Upsilon mesons at the Fermilab Tevatron is considered, and the comparisions of calculated $p_T$-distributions and spin alignment parameter $α$ with the D0 experimental data are shown. We argue that measuring the double cross section and the polarization of upsilonium states can serve as a crucial test discriminating two competing theoretical approaches to parton dynamics in QCD.

hep-ph↗
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↗