Associated photon and heavy quark production at high energy within kT-factorization

Lipatov, A. V.; Malyshev, M. A.; Zotov, N. P.

doi:10.1063/1.4802162

Cited by 38 publications

(83 citation statements)

References 6 publications

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“…The certain advantages are connected with the fact that, even with the LO partonic amplitudes, one can include a large piece of higher-order corrections (namely, part of NLO + NNLO + ... terms containing leading log 1/x enhancement of cross sections due to real initial state gluon emissions) taking them into account in the form of CCFM-evolved transverse momentum dependent (TMD) gluon densities. In particular, it gives better agreement with Tevatron data on the associated production of prompt photons and charm or beauty quarks compared to the NLO pQCD predictions [15], that is an additional motivation of our present study.…”

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confidence: 57%

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Z-boson production in association with heavy flavor in thek_T-factorization

2017

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Abstract. We present the calculations of associated production of Z bosons and heavy (charm or beauty) quarks at the LHC energies in the framework of k T -factorization QCD approach. Our consideration is mainly based on the O(αα 2 s ) off-shell gluon-gluon fusion subprocess g * g * → ZQQ, where produced Z boson subsequently decays into a lepton pair. Several subleading contributions from the O(αα 2 s ) and O(αα 3 s ) subprocesses are taken into account. Contributions from the double parton scattering mechanism are estimated. The transverse momentum dependent (or unintegrated) gluon densities in a proton are determined using the Catani-Ciafaloni-Fiorani-Marchesini evolution equation. We achieve reasonably good agreement of our predictions and latest experimental data taken by the CMS and ATLAS Collaborations, discuss the theoretical uncertainties of our calculations and demonstrate the importance of subleading quark contributions in description of the LHC data in the whole kinematical region.Very recently, the CMS Collaboration has presented the measurements of Z boson production in association with charm [1] quarks at the LHC energy √ s = 8 TeV. Also measurements of angular correlations of B-hadrons at √ s = 7 TeV were presented [2] and the ATLAS Collaboration has reported the experimental data on the total and differential cross sections of Z boson production in association with beauty quark jets at √ s = 7 TeV [3]. Such processes involve both strong and weak interactions, so are important as global test of the Standard Model (SM). The Z + b-jets production is an important background for studies of the associated production of Higgs and Z bosons, where the Higgs boson decays into bb pairs [4][5][6]. Many physics scenarios beyond the Standard Model (SM), for example, new generations of heavy quarks (b ′ , t ′ ) decaying into Z bosons and b-quarks [7], supersymmetric Higgs bosons produced in association with beauty quarks [8] and some SM extentions with additional S U(2) doublets with enhanced Zbb coupling [9], predict final states with b-quarks and Z bosons. In addition, Z + b/Z + c cross sections ratio is highly sensitive to the charm content of the proton [10]. Finally, such processes may serve as potential indicators of the Double Parton Scattering (DPS) mechanism [11][12][13].In the present work we analyse recent CMS [1, 2] and ATLAS [3] data using so called k Tfactorization QCD approach [14]. This approach is based on the famous Balitsky-Fadin-KuraevLipatov (BFKL) or Ciafaloni-Catani-Fiorani-Marchesini (CCFM) gluon evolution equations and pro-⋆

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confidence: 57%

“…Thus, we rely on a combination of two techniques with each of them being used where it is most suitable. For the subprocesses (2) and (3) we use here the on-shell limit of formulas obtained earlier [15] supplementing them with the Z boson decays.…”

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confidence: 99%

Z-boson production in association with heavy flavor in thek_T-factorization

2017

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“…It was shown very recently [10] that the k t -factorization formalism with commonly used UGDFs (Kimber-Martin-Ryskin (KMR) [11] and Jung CCFM [12]) gives a reasonable description of recent ATLAS data obtained at √ s = 8 TeV [13]. We perform similar calculation and, as will be seen in the following, draw rather different conclusions.…”

Section: Introductionmentioning

confidence: 60%

Inclusive production of Higgs boson in the two-photon channel at the LHC withinκt-factorization approach and with the standard model couplings

2014

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We calculate differential cross sections for Higgs boson and/or two-photon production from intermediate (virtual) Higgs boson within the formalism of k t -factorization. The off-shell g * g * → H matrix elements are used. We compare results obtained with infinite top fermion (quark) mass and with finite mass taken into account. The latter effect is rather small. We compare results with different unintegrated gluon distributions from the literature. Two methods are used. In the first method first Higgs boson is produced in the 2 → 1 gg → H k t -factorization approach and then isotropic decay with the Standard Model branching fraction is performed. In the second method we calculate directly two photons coupled to the virtual Higgs boson. The results of the two methods are compared and differences are discussed. The results for two photons from the Higgs boson are compared with recent ATLAS collaboration data. In contrast to a recent calculation the leading order gg → H contribution is rather small compared to the ATLAS experimental data (γγ transverse momentum and rapidity distributions) for all unintegrated gluon distributions from the literature. We include also higher-order contribution gg → H(→ γγ)g, gg → gHg and the contribution of the W + W − and Z 0 Z 0 . The gg → Hg mechanism gives similar cross section as the gg → H mechanism. We argue that there is almost no double counting when adding gg → H and gg → Hg contributions due to different topology of Feynman diagrams. The final sum is comparable with the ATLAS two-photon data. We discuss uncertainties related to both the theoretical approach and existing UGDFs.

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“…The cross sections for isolated-photon production in photoproduction have been calculated to nextto-leading order (NLO) by Fontannaz, Guillet and Heinrich (FGH) [13][14][15]. Calculations based on the k T -factorisation approach have been made by Lipatov, Malyshev and Zotov (LMZ) [16][17][18][19].…”

Section: Jhep08(2014)023mentioning

confidence: 99%

“…Fragmentation terms and the quark content of the resolved photon are not included, but the box diagram is included together with 2 → 3 subprocesses to represent the LO direct and resolved photon contributions. The calculation used in the previous ZEUS analysis [1] has been augmented by a term that takes account of the gluon content of the resolved photon, and further technical changes have been implemented [19]. Uncertainties associated with the hard scale were provided by the authors.…”

Section: Theoretical Modelsmentioning

confidence: 99%

Further studies of the photoproduction of isolated photons with a jet at HERA

Abramowicz¹,

Abt²,

Adamczyk³

et al. 2014

J. High Energ. Phys.

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In this extended analysis using the ZEUS detector at HERA, the photoproduction of isolated photons together with a jet is measured for different ranges of the fractional photon energy, x meas γ , contributing to the photon-jet final state. Cross sections are evaluated in the photon transverse-energy and pseudorapidity ranges 6 < E γ T < 15 GeV and −0.7 < η γ < 0.9, and for jet transverse-energy and pseudorapidity ranges 4 < E jet T < 35 GeV and −1.5 < η jet < 1.8, for an integrated luminosity of 374 pb −1 . The kinematic observables studied comprise the transverse energy and pseudorapidity of the photon and the jet, the azimuthal difference between them, the fraction of proton energy taking part in the interaction, and the difference between the pseudorapidities of the photon and the jet. Higher-order theoretical calculations are compared to the results.

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Associated photon and heavy quark production at high energy within kT-factorization

Cited by 38 publications

References 6 publications

Z-boson production in association with heavy flavor in thek_T-factorization

Z-boson production in association with heavy flavor in thek_T-factorization

Inclusive production of Higgs boson in the two-photon channel at the LHC withinκt-factorization approach and with the standard model couplings

Further studies of the photoproduction of isolated photons with a jet at HERA

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Associated photon and heavy quark production at high energy within kT-factorization

Cited by 38 publications

References 6 publications

Z-boson production in association with heavy flavor in thekT-factorization

Z-boson production in association with heavy flavor in thekT-factorization

Inclusive production of Higgs boson in the two-photon channel at the LHC withinκt-factorization approach and with the standard model couplings

Further studies of the photoproduction of isolated photons with a jet at HERA

Contact Info

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Z-boson production in association with heavy flavor in thek_T-factorization

Z-boson production in association with heavy flavor in thek_T-factorization