The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
A. V. Nesterenko - One of the best experts on this subject based on the ideXlab platform.
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Recurrent form of the renormalization group relations for the higher-order hadronic vacuum Polarization Function perturbative expansion coefficients
Journal of Physics G: Nuclear and Particle Physics, 2020Co-Authors: A. V. NesterenkoAbstract:The renormalization group relations for the higher-order hadronic vacuum Polarization Function perturbative expansion coefficients are studied. The folded recurrent and unfolded explicit forms of such relations are obtained. The explicit expression for the coefficients, which incorporate the contributions of the $\pi^{2}$-terms in the perturbative expansion of the R-ratio of electron-positron annihilation into hadrons, is derived at an arbitrary loop level.
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Hadronic vacuum Polarization Function within dispersive approach to QCD
Journal of Physics G: Nuclear and Particle Physics, 2015Co-Authors: A. V. NesterenkoAbstract:The dispersive approach to quantum chromodynamics is applied to the study of the hadronic vacuum Polarization Function and associated quantities. This approach merges the intrinsically nonperturbative constraints, which originate in the kinematic restrictions on the respective physical processes, with corresponding perturbative input. The obtained hadronic vacuum Polarization Function agrees with pertinent lattice simulation data. The evaluated hadronic contributions to the muon anomalous magnetic moment and to the shift of the electromagnetic fine structure constant conform with recent assessments of these quantities.
J J Toscano - One of the best experts on this subject based on the ideXlab platform.
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gauge invariant approach to the beta Function in yang mills theories with universal extra dimensions
Physical Review D, 2020Co-Authors: M Huertaleal, H Novalessanchez, J J ToscanoAbstract:The radiative correction to the beta Function is comprehensively studied at the one-loop level in the context of universal extra dimensions. Instead of using cutoffs to regularize one-loop divergences, the dimensional regularization scheme is used. In this approach, large momenta effects are removed from physical amplitudes by adjusting the parameters of the appropriate counterterms. The use of a $\mathrm{SU}(N)$-covariant gauge-fixing procedure to quantize the theory is stressed. One-loop contributions of Kaluza-Klein (KK) excitations are characterized by discrete KK sums and continuous momenta sums, which can diverge. Two types of ultraviolet divergences are identified, one arising from poles of the gamma Function and associated with short-distance effects in the usual four-dimensional spacetime manifold and the other emerging either from poles of the one-dimensional Epstein Function or from the gamma Function and corresponding to short-distance effects in the compact manifold. We address the cases of 5 and $4+n$ dimensions ($n\ensuremath{\ge}2$) separately. In five dimensions, the one-dimensional Epstein Function is convergent, so the usual counterterm renormalizes the vacuum-Polarization Function. For $4+n$ dimensions, the one-dimensional Epstein Function is divergent, so renormalization is implemented by interactions of canonical dimension higher than 4, already present in the effective theory. The Polarization Function is renormalized using both a mass-dependent scheme and a mass-independent scheme, with extra-dimensions effects decoupling in the former case but not in the latter. The beta Function is calculated for an arbitrary number of extra dimensions. Our main result is that Yang-Mills theory remains perturbative at the one-loop level, which is in disagreement with the results obtained in the literature by using a cutoff regulator, which suggest that Yang-Mills theory in more than four dimensions ceases to be perturbative. We emphasize the advantages of a mass-dependent scheme in this type of theories, in which decoupling is manifest.
S.a. Larin - One of the best experts on this subject based on the ideXlab platform.
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The three loop QED contributions to the photon vacuum Polarization Function in the MS scheme and the four loop corrections to the QED beta Function in the on-shell scheme
Physics Letters B, 1991Co-Authors: S.g. Gorishnii, S.a. Larin, A.l. KataevAbstract:We present the three-loop analytical QED results for the asymptotic expression of the photon vacuum Polarization Function Π in the MS -scheme. Using the recently obtained four-loop results for the QED β-Function in the MS-like and MOM schemes (β MS− and Ψ-Functions) and for ( g −2) μ we get the four-loop QED β-Function in the on-shell scheme.
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the analytical contribution of the three loop diagrams with two fermion circles to the photon propagator and to the eighth order correction to the muon anomalous magnetic moment
Physics Letters B, 1991Co-Authors: R N Faustov, A.l. Kataev, S.a. Larin, V V StarshenkoAbstract:Abstract Using the renormalization group relations between the QED β-Functions in different renormalization schemes and the previously obtained result for the four-loop contribution to the β-Function in the on-shell scheme βOS we obtain the analytical contributions of the three-loop QED diagrams with two fermion circles to the photon vacuum Polarization Function in the on-shell scheme and to the eighth-order correction to the muon anomalous magnetic moment aμ. The result for aμ disagrees with the result of the recent numerical computations. The origin of this disagreement is commented on. The corrected expression for the cubic in the contribution of the number of leptons to the QED βOS-Function is presented.
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The three-loop QED photon vacuum Polarization Function in the MS-scheme and the four-loop QED β-Function in the on-shell scheme
Physics Letters B, 1991Co-Authors: S.g. Gorishny, A.l. Kataev, S.a. LarinAbstract:Abstract We present the three-loop analytical QED results for the asymptotic expression of the photon vacuum Polarization Function Π in the MS -scheme. Using the recently obtained four-loop results for the QED β-Function in the MS-like and MOM schemes (βMS− and Ψ-Functions) and for (g−2)μ we get the four-loop QED β-Function in the on-shell scheme.
A.l. Kataev - One of the best experts on this subject based on the ideXlab platform.
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The three loop QED contributions to the photon vacuum Polarization Function in the MS scheme and the four loop corrections to the QED beta Function in the on-shell scheme
Physics Letters B, 1991Co-Authors: S.g. Gorishnii, S.a. Larin, A.l. KataevAbstract:We present the three-loop analytical QED results for the asymptotic expression of the photon vacuum Polarization Function Π in the MS -scheme. Using the recently obtained four-loop results for the QED β-Function in the MS-like and MOM schemes (β MS− and Ψ-Functions) and for ( g −2) μ we get the four-loop QED β-Function in the on-shell scheme.
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the analytical contribution of the three loop diagrams with two fermion circles to the photon propagator and to the eighth order correction to the muon anomalous magnetic moment
Physics Letters B, 1991Co-Authors: R N Faustov, A.l. Kataev, S.a. Larin, V V StarshenkoAbstract:Abstract Using the renormalization group relations between the QED β-Functions in different renormalization schemes and the previously obtained result for the four-loop contribution to the β-Function in the on-shell scheme βOS we obtain the analytical contributions of the three-loop QED diagrams with two fermion circles to the photon vacuum Polarization Function in the on-shell scheme and to the eighth-order correction to the muon anomalous magnetic moment aμ. The result for aμ disagrees with the result of the recent numerical computations. The origin of this disagreement is commented on. The corrected expression for the cubic in the contribution of the number of leptons to the QED βOS-Function is presented.
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The three-loop QED photon vacuum Polarization Function in the MS-scheme and the four-loop QED β-Function in the on-shell scheme
Physics Letters B, 1991Co-Authors: S.g. Gorishny, A.l. Kataev, S.a. LarinAbstract:Abstract We present the three-loop analytical QED results for the asymptotic expression of the photon vacuum Polarization Function Π in the MS -scheme. Using the recently obtained four-loop results for the QED β-Function in the MS-like and MOM schemes (βMS− and Ψ-Functions) and for (g−2)μ we get the four-loop QED β-Function in the on-shell scheme.
K. G. Chetyrkin - One of the best experts on this subject based on the ideXlab platform.
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Recent progress in computing four-loop massive correlators
Nuclear Physics B - Proceedings Supplements, 2007Co-Authors: K. G. Chetyrkin, J. H. Kühn, Christian SturmAbstract:We report about recent progress in computing four-loop massive correlators. The expansion of these correlators in the external momentum leads to vacuum integrals. The calculation of these vacuum integrals can be used to determine Taylor expansion coefficients of the vacuum Polarization Function and decoupling Functions in perturbative Quantum chromodynamics. New results at four-loop order for the lowest Taylor expansion coefficient of the vacuum Polarization Function and for the decoupling relation are presented.
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Four-loop moments of the heavy quark vacuum Polarization Function in perturbative QCD
The European Physical Journal C, 2006Co-Authors: K. G. Chetyrkin, J. H. Kühn, Christian SturmAbstract:New results at four-loop order in perturbative QCD for the first two Taylor coefficients of the heavy quark vacuum Polarization Function are presented. They can be used to perform a precise determination of the charm- and bottom-quark mass. Implications for the value of the quark masses are briefly discussed.
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Recent Results on Four-loop Tadpoles
Nuclear Physics B - Proceedings Supplements, 2006Co-Authors: K. G. Chetyrkin, J. H. Kühn, Christian SturmAbstract:The experimental measurable R -ratio can be used to perform a precise determination of the charm- and bottom-quark mass with the help of theoretical computable expansion coefficients of the vacuum Polarization Function. The four-loop contributions in perturbative QCD to the first two expansion coefficients of the vacuum Polarization Functions are presented.
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three loop Polarization Function and cal o alpha_s 2 corrections to the production of heavy quarks
arXiv: High Energy Physics - Phenomenology, 1996Co-Authors: K. G. Chetyrkin, J H Kuehn, Matthias SteinhauserAbstract:The three-loop vacuum Polarization Function $\Pi(q^2)$ induced by a massive quark is calculated. A comprehensive description of the method is presented. From the imaginary part the ${\cal O}(\alpha_s^2)$ result for the production of heavy quarks $R(s)=\sigma(e^+e^-\to \mbox{hadrons})/\sigma(e^+e^-\to \mu^+\mu^-)$ can be extracted. Explicit formulae separated into the different colour factors are given.
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Three-loop Polarization Function and O(αs2) corrections to the production of heavy quarks
Nuclear Physics B, 1996Co-Authors: K. G. Chetyrkin, Jens H. Kuhn, Matthias SteinhauserAbstract:Abstract The three-loop vacuum Polarization Function Π ( q 2 ) induced by a massive quark is calculated. A comprehensive description of the method is presented. From the imaginary part the O ( α s 2 ) result for the production of heavy quarks R ( s ) = σ ( e + e − → hadrons)/ σ ( e + e − → μ + μ − ) can be extracted. Explicit formulae separated into the different colour factors are given.