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Maxim Nefedov

Publications and source records attributed to Maxim Nefedov.

36 records · Page 2Linked to original sources
arXiv2020

Towards stability of NLO corrections in High-Energy Factorization via Modified Multi-Regge Kinematics approximation

The perturbatively-stable scheme of Next-to-Leading order (NLO) calculations of cross-sections for multi-scale hard-processes in DIS-like kinematics is developed in the framework of High-Energy Factorization. The evolution equation for unintegrated PDF, which resums $\log 1/z$-corrections to the coefficient function in the Leading Logarithmic approximation together with a certain subset of Next-to-Leading Logarithmic and Next-to-Leading Power corrections, necessary for the perturbative stability of the formalism, is formulated and solved in the Doubly-Logarithmic approximation. An example of DIS-like process, induced by the operator ${\rm tr}\left[G_{μν}G^{μν}\right]$, which is sensitive to gluon PDF already in the LO, is studied. Moderate ($O(20\%)$) NLO corrections to the inclusive structure function are found at small $x_B<10^{-4}$, while for the $p_T$-spectrum of a leading jet in the considered process, NLO corrections are small ($<O(20\%)$) and LO of $k_T$-factorization is a good approximation. The approach can be straightforwardly extended to the case of multi-scale hard processes in $pp$-collisions at high energies.

hep-ph↗
arXiv2019

Off-shell initial state effects and gauge invariance in the Drell-Yan process

The Helicity Structure Functions in the Drell-Yan process are discussed in a framework of Parton Reggeization Approach, which includes the transverse momentum of initial-state partons in a way compatible with QED gauge-invariance. Relationships with conventional Transverse Momentum Dependent Parton Model formalism are clarified.

hep-ph↗
arXiv2019

Computing one-loop corrections to effective vertices with two scales in the EFT for Multi-Regge processes in QCD

The computation of one-loop corrections to Reggeon-Particle-Particle effective vertices with two scales of virtuality is considered in the framework of gauge-invariant effective field theory for Multi-Regge processes in QCD. Rapidity divergences arising in loop integrals are regulated by "tilted Wilson lines" prescription. General analysis of rapidity divergences at one loop is given and necessary scalar integrals with one and two scales of virtuality are computed. Two examples of effective vertices at one loop are considered: the effective vertex of interaction of (space-like) virtual photon with one Reggeized and one Yang-Mills quark and the effective vertex of Reggeized gluon to Yang-Mills gluon transition with an insertion of the operator ${\rm tr}\left[G_{μν}G^{μν} \right]$ carrying the (space-like) off-shell momentum. All terms $\sim r^{\pmε}$ in the rapidity-regulator variable $r$ cancel between diagrams and only $\log r$-divergence is left. It is checked on several examples, that obtained results indeed allow one to reproduce Regge limit of one-loop QCD scattering amplitudes.

hep-ph↗
arXiv2019

One-loop corrections to multiscale effective vertices in the EFT for Multi-Regge processes in QCD

The computation of one-loop corrections to the $γ^\star Q_+ q$ and $gR_+g$ effective vertices in the framework of gauge-invariant effective theory for Multi-Regge processes in QCD is reviewed. Due to consistent implementation of the "tilted Wilson line" regularization for rapidity divergences, the gauge-invariance has been preserved at all stages of calculation independently on the rapidity regulator and cancellation of the power-like dependence on the regularization variable is traced. Only single-logarithmic rapidity divergence is left in the final result.

hep-ph↗
arXiv2019

Evidence in favor of Single Parton Scattering mechanism in $Υ$ and $D$ associated production at the LHC

Associated production of prompt $Υ(1S)$ and $D^{+,0}$ mesons has been proposed as a golden channel for the search of Double Parton Scattering, because Single Parton Scattering contribution to the cross-section is believed to be negligible on a basis of leading order calculations in the Collinear Parton Model. We study this process in the leading order approximation of the Parton Reggeization Approach. Hadronization of $b\bar{b}$-pair into bottomonium states is described within framework of the NRQCD-factorization approach while production of $D$ mesons is described in the fragmentation model with scale-dependent fragmentation functions. We have found good agreement with LHCb data for various normalized differential distributions, except for the case of spectra on azimuthal angle differences at the small $Δφ$ values. Crucially, the total cross-section in our Single Parton Scattering model accounts for more than one half of observed cross-section, thus dramatically shrinking the room for Double Parton Scattering mechanism.

hep-ph↗
arXiv2018

Correlation observables in $ΥD$ pair production at the LHC within the parton Reggeization approach

We study angular correlations in associated hadroproduction of $Υ(1S)$ with the $D^{\pm}$ and $D^0$-mesons at the LHC in the Leading Order of the parton Reggeization approach. Hadronization of $b\bar{b}$-pair to $Υ(1S)$ is described within the NRQCD-factorization framework. Production of $D-$mesons is described in the fragmentation model with scale-dependent fragmentaion functions. We have found good agreement with LHCb data for various differential distributions, except for the case of spectra on azimuthal angle differences at the small $\triangleφ$ values. The total cross-section in our Single Parton Scattering model, calculated under conservative assumptions, accounts for almost one half of observed cross-section, thus dramatically shrinking the room for Double Parton Scattering mechanism.

hep-ph↗
arXiv2018

Off-shell initial state effects, gauge invariance and angular distributions in the Drell-Yan process

We discuss production of Drell-Yan lepton pairs at hadron colliders in the framework of the parton Reggeization approach, which includes off-shell initial state effects in a gauge-invariant way. Other possible prescriptions to restore gauge-invariance of hard-scattering coefficient with off-shell initial-state partons are also investigated and significant differences for the resulting structure functions are found, especially for the $F_{UU}^{(\cos2ϕ)}$. We compare our numerical results for $q_T$-spectra of the lepton pair with experimental data, obtained by E-288 collaboration ($\sqrt{S}=19.4$ and 23.8 GeV) and find a good agreement. Also we perform predictions for the Drell-Yan structure functions at NICA $pp$-collider ($\sqrt{S}=24$ GeV).

hep-ph↗
arXiv2017

DIS structure functions in the NLO approximation of the Parton Reggeization Approach

The main ideas of the NLO calculations in Parton Reggeization Approach are illustrated on the example of the simplest NLO subprocess, which contributes to DIS: $γ^\star+R\to q + \bar{q}$. The double counting with the LO contribution $γ^\star + Q \to q$ is resolved. The problem of matching of the NLO results for single-scale observables in the Parton Reggeization Approach on the corresponding NLO results in the Collinear Parton Model is considered. In the developed framework, the usual NLO PDFs in the $\overline{MS}$-scheme can be consistently used as the collinear input for the NLO calculation in the Parton Reggeization Approach.

hep-ph↗
arXiv2017

On the one-loop calculations with Reggeized quarks

The technique of one-loop calculations for the processes involving Reggeized quarks is described in the framework of gauge invariant effective field theory for the Multi-Regge limit of QCD, which has been introduced by Lipatov and Vyazovsky. The rapidity divergences, associated with the terms enhanced by $\log (s)$, appear in the loop corrections in this formalism. The covariant procedure of regularization of rapidity divergences, preserving the gauge invariance of effective action is described. As an example application, the one-loop correction to the propagator of Reggeized quark and $γQ q$-scattering vertex are computed. Obtained results are used to construct the Regge limit of one-loop $γγ\to q\bar q$ amplitude. The cancellation of rapidity divergences and consistency of the effective field theory prediction with the full QCD result is demonstrated. The rapidity renormalization group within the effective field theory is discussed.

hep-th↗
arXiv2017

$B{\bar B}$ angular correlations at the LHC in parton Reggeization approach merged with higher-order matrix elements

We calculate the angular distribution spectra between beauty ($B$) and anti-beauty ($\bar B$) mesons in proton-proton collisions in the leading order approximation of the parton Reggeization approach consistently merged with the next-to-leading order corrections from the emission of additional hard gluon. To describe b-quark hadronization we use the universal scale-depended parton-to-meson fragmentation functions extracted from the world $e^+e^-$ annihilation data. We have obtained good agreement between our predictions and data from the CMS Collaboration at the energy $\sqrt{S}=7$ TeV for $B \bar B$ angular correlations within uncertainties and without free parameters. Predictions for analogous correlation observables at $\sqrt{S}=13$ TeV are provided.

hep-ph↗
arXiv2017

Heavy quark production at the LHC in the Parton Reggeization Approach

We present the general introduction to the Parton Reggeization Approach and discuss some new results on large-p_T production for heavy quarks at the LHC. We concentrate here on study of different correlation spectra for b\barb-jet pairs, D\barD-meson pairs and DD-meson pairs.

hep-ph↗
arXiv2016

Towards NLO calculations in the parton Reggeization approach

Parton Reggeization approach is the scheme of kT-factorization for multiscale hard processes, which is based on the Lipatov's gauge invariant effective field theory (EFT) for high energy processes in QCD. The new type of rapidity divergences, associated with the log 1/x-corrections, appears in the loop corrections in this formalism. The covariant procedure of regularization of rapidity divergences, preserving the gauge invariance of effective action is described. As an example application, the one-loop correction to the propagator of Reggeized quark and gamma Q q -scattering vertex are computed. Obtained results are used to construct the Regge limit of one-loop gamma+gamma -> q + barq amplitude. The cancelation of rapidity divergences and consistency of the EFT prediction with the full QCD result is demonstrated. The rapidity renormalization group within the EFT is discussed.

hep-ph↗
arXiv2015

Diphoton production at Tevatron and the LHC in the NLO* approximation of the Parton Reggeization Approach

The hadroproduction of prompt isolated photon pairs at high energies is studied in the NLO* framework of the Parton Reggeization Approach. The real part of the NLO corrections is computed, and the procedure for the subtraction of double counting between real parton emissions in the hard-scattering matrix element and unintegrated PDF is constructed for the amplitudes with Reggeized quarks in the initial state. The matrix element of the important NNLO subprocess RR->2gamma with full dependence on the transverse momenta of the initial-state Reggeized gluons is obtained. We compare obtained numerical results with diphoton spectra measured at Tevatron and the LHC, and find a good agreement of our predictions with experimental data at the high values of diphoton transverse momentum, pT, and especially at the pT larger than the diphoton invariant mass, M. In this multi-Regge kinematics region, the NLO correction is strongly suppressed, demonstrating the self-consistency of the Parton Reggeization Approach.

hep-ph↗
arXiv2014

B-meson production in the Parton Reggeization Approach at Tevatron and the LHC

We study the inclusive hadroproduction of $B^0$, $B^+$, and $B_s^0$ mesons at leading order in the parton Reggeization approach using the universal fragmentation functions extracted from the combined $e^+e^-$ annihilation data from CERN LEP1 and SLAC SLC colliders. We have described $B$-meson transverse momentum distributions measured in the central region of rapidity by the CDF Collaboration at Fermilab Tevatron and CMS Collaboration at LHC within uncertainties and without free parameters, applying Kimber-Martin-Ryskin unintegrated gluon distribution function in a proton. The forward $B$-meson production ($2.0<y<4.5$) measured by the LHCb Collaboration also has been studied and expected disagreement between our theoretical predictions and data has been obtained.

hep-ph↗
arXiv2014

Open charm production in the parton Reggeization approach: from Tevatron to LHC

We study the inclusive hadroproduction of D^0, D^+, D^star+, and D_s^+ mesons at leading order in the parton Reggeization approach endowed with universal fragmentation functions fitted to $e^+e^-$ annihilation data from CERN LEP1. We have described $D$-meson transverse momentum distributions measured in the central region of rapidity by the CDF Collaboration at Tevatron (|y|<1) and ALICE Collaboration at LHC (|y|<0.5) within uncertainties and without free parameters, using Kimber-Martin-Ryskin unintegrated gluon distribution function in a proton. The forward D-meson production (|y|>2.0) measured by the LHCb Collaboration also has been studied and expected disagreement between our theoretical predictions and data has been obtained.

hep-ph↗
arXiv2014

Heavy quarkonium production at the LHC in the framework of NRQCD and parton Reggeization approach

Heavy quarkonium production in the framework of the nonrelativistic quantum chromodynamics and leading order of the parton Reggeization approach at the Tevatron and LHC Colliders is discussed. The new results, which are reviewed in this report, include the comparison with recent data on chi_{c1,c2} production from ATLAS Collaboration and special discussion of heavy quarkonium polarization issues in the considered framework.

hep-ph↗
arXiv2013

Prompt Upsilon(nS) production at the LHC in the Regge limit of QCD

We study prompt Upsilon(nS) hadroproduction (n=1,2,3) invoking the hypothesis of gluon Reggeization in t-channel exchanges at high energy and the factorization formalism of nonrelativistic quantum chromodynamics at leading order in the strong-coupling constant alpha_s and the relative velocity v of the bound quarks. The transverse-momentum distributions of prompt Upsilon(nS)-meson production measured by the ATLAS Collaboration at the CERN LHC are fitted to obtain the color-octet nonperturbative long-distance matrix elements, which are used to predict prompt Upsilon(nS) production spectra measured by the CMS and LHCb Collaborations. At the numerical calculation, we adopt the Kimber-Martin-Ryskin prescription to derive unintegrated gluon distribution function of the proton from its collinear counterpart, for which we use the Martin-Roberts-Stirling-Thorne set. We find good agreement with measurements by the ATLAS, CMS and LHCb Collaborations at the LHC at the hadronic c.m. energy sqrt S=7 TeV as well as with measurements by the CDF Collaboration at the Fermilab Tevatron.

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