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A. L. Kataev

Publications and source records attributed to A. L. Kataev.

108 records · Page 6Linked to original sources
arXiv1998

Testing non-perturbative strong interaction effects via the Adler function

Based on the compilation of the available e^+e^- data, we present a non-perturbative estimation of the Adler function derived from the electromagnetic current correlator, and compare it with theoretical predictions from perturbative QCD (pQCD). The comparison is presented for the Euclidean region where pQCD is supposed to work best. We emphasize that such a comparison only makes sense if one takes into account the exact mass dependence of the perturbative predictions, which are available for the leading and next to leading (two-loop) order. In order to have the correct physical mass dependence in the evolution of the strong coupling as well, we utilize the MOM scheme beta-function to two-loops calculated recently. Three-loop effects, which are available as series expansions for low and high momentum transfer, are included by using Pade improvement. We discuss possible constraints on non-perturbative effects as suggested by the operator product expansion.

hep-ph↗
arXiv1998

The QCD analysis of the CCFR data for $xF_3$: higher twists and $α_s(M_Z)$ extractions at the NNLO and beyond

The improved next-to-next-to-leading order (NNLO) QCD analysis of the experimental data of the CCFR collaboration for the $xF_3$ structure function is made. Theoretical ambiguities of the NNLO fits are estimated by means of the Padé resummation technique, which was applied both in the expanded and non-expanded forms. The NNLO and the new N$^3$LO $α_s(Q^2)$ $\bar{MS}$-matching conditions are used. In the process of the fits we are taking into account the target mas corrections and the twist-4 $1/Q^2$-terms. Our NNLO results for $α_s(M_Z)$ values, extracted from the CCFR $xF_3$ data, are $α_s(M_Z)=0.118 \pm 0.002 (stat)\pm 0.005 (syst) \pm 0.003(theory)$ provided the twist-4 contributions are fixed through the infrared renormalon model and $α_s(M_Z)=0.116^{+ 0.006}_{-0.007}(stat)\pm 0.005 (syst) \pm 0.004(theory)$ provided the twist-4 terms are considered as the free parameters. It is shown that the extracted at the NNLO order $x$-shape of the twist-4 correction is almost unchanged after application of the Padé resummation approximant.

hep-ph↗
arXiv1998

QCD Sum Rules and Hadronic Radial Excitations of Light Mesons

We reminde definite results related to the low-energy hadronic phenomenology, obtained using the QCD sum rules methods. We emphasize that these results can be of interest for the comparison with available and new experimental results, obtained in part by the experimentalists of IHEP (Protvino).

hep-ph↗
arXiv1997

The QCD analysis of the revised CCFR data for xF_3 structure function: the next-to-next-to-leading order and Padé approximants

The next-to-next-to-leading order (NNLO) QCD analysis of the revised experimental data of the CCFR collaboration for the $xF_3$ structure function of the deep-inelastic scattering of neutrinos and antinuetrinos on the nucleons is made by means of the Jacobi polynomial expansion technique. The NNLO values of the QCD coupling constant are determined both without and with twist--4 contributions taken into account. Theoretical ambiguities of $α_s$ are fixed using the methods of the Padé approximants. We observe that the [0/2] Padé approximant is more appropriate for this purpose than the [1/1] one.

hep-ph↗
arXiv1997

The order $O(\barα~\barα_s)$ and $O(\barα^2)$ corrections to the decay width of the neutral Higgs boson to the $\bar{b}b$ pair

We present the analytical expressions for the contributions of the order $O(\barα~\barα_s)$ and $O(\barα^2)$ corrections to the decay width of the Standard Model Higgs boson into the $\bar{b}b$-pair. The numerical value of the mixed QED and QCD correction of order $O(\barα~\barα_s)$ is comparable with the previously calculated terms in the perturbative series for $Γ(H^0\to\bar{b}b)$.

hep-ph↗
arXiv1997

Next-to-next-to-leading order QCD analysis of the revised CCFR data for xF_3 structure function and the higher twist contributions

We present the results of the next-to-next-to-leading order QCD analysis of the recently revised experimental data of the CCFR collaboration for the $xF_3$ structure function using the Jacobi polynomial expansion method. The effects of the higher twist contributions are included into the fits following the infrared renormalon motivated model. The special attention is paid to the checks of the predictive abilities of the infrared renormalon model and to the independent extraction of the $x$-shape of the twist-4 contributions to the $xF_3$ structure function in the process of the leading order, next-to-leading order and next-to-next-to-leading order fits of the revised CCFR data. We stress that at the next-to-next-to-leading order the results for $α_s(M_Z)$ turn out to be almost nonsensitive to the higher-twist terms. We obtain the following result $α_s(M_Z)^{NNLO}=0.117 \pm 0.002(stat) \pm 0.005 (syst)\pm 0.003 (theory)$. The comparison of the outcomes of our next-to-leading order and next-to-next-to-leading order analysis indicate that the theoretical QCD uncertainties were underestimated in the process of the next-to-leading order determination of $α_s(M_Z)$, made recently by the CCFR collaboration itself.

hep-ph↗
arXiv1996

Next-to-next-to-leading order QCD analysis of the CCFR data for xF_3 and F_2 structure functions of the deep-inelastic neutrino-nucleon scattering

The next-to-next-to-leading order (NNLO) non-singlet QCD analysis of the experimental data of the CCFR collaboration for the $xF_3$ and $F_2$ structure functions of the deep-inelastic scattering of neutrinos and antineutrinos on the nucleon by means of the Jacobi polinomial expansion method is made. The target mass corrections are also taken into account. We demonstrate that the NNLO corrections have the important: they are decreasing the difference between the values of $α_s(M_Z)$, extracted from the NLO fit of $xF_3$ data and from the NLO non-singlet fit of the combined $xF_3$ and $F_2$ CCFR data. The obtained NNLO results for $α_s(M_Z)$ are :$α_s(M_Z)=0.109 \pm 0.003(stat) \pm 0.005(syst) \pm 0.003 (theor)$ (from $xF_3$ data) and $α_s(M_Z)=0.111\pm 0.002 (stat) \pm 0.003 (syst) \pm 0.003 (theor)$ (from the combined $xF_3$ and $F_2$ data). We also estimate the values of the order $O(α_s^2)$-corrections to the Gottfried sum rule.

hep-ph↗
arXiv1995

The Generalized Crewther Relation in QCD and its Experimental Consequences

We use the BLM scale-fixing prescription to derive a renormalization-scheme invariant relation between the coefficient function for the Bjorken sum rule for polarized deep inelastic scattering and the $R$-ratio for the $e^+e^-$ annihilation cross section. This relation provides a generalization of the Crewther relation to non-conformally invariant gauge theories. The derived relations allow one to calculate unambiguously without renormalization scale or scheme ambiguity the effective charges of the polarized Bjorken and the Gross-Llewellen Smith sum rules from the experimental value for the effective charge associated with $R$-ratio. Present data are consistent with the generalized Crewther relations, but measurements at higher precision and energies will be needed to decisively test these fundamental relations in QCD.

hep-ph↗
arXiv1995

On Connection between Coefficient Functions for Deep-Inelastic and Annihilation Processes

It has been shown that the one-loop behavior of the axial anomaly, occurring when the axial current is appropriately normalized, leads to the cancellation of the corrections of type $C_F^N{\bar α}_s^N,~~ (N\geq 1) $ in the Crewther relation for the coefficient functions of deep-inelastic and annihilation processes. The arguments in favour of the overall factorization of the factor $β({\bar α}_s)/ {\bar α}_s$ in all orders of perturbation theory in this relation are presented.

hep-ph↗
arXiv1995

Estimates of the higher-order QCD corrections to R(s), R_τ and deep-inelasstic scattering sum rules

We present the attempt to study the problem of the estimates of higher-order perturbative corrections to physical quantities in the Euclidean region. Our considerations are based on the application of the scheme-invariant methods, namely the principle of minimal sensitivity and the effective charges approach. We emphasize, that in order to obtain the concrete results for the physical quantities in the Minkowskian region the results of application of this formalism should be supplemented by the explicite calculations of the effects of the analytical continuation. We present the estimates of the order $O(α^{4}_{s})$ QCD corrections to the Euclidean quantities: the $e^+e^-$-annihilation $D$-function and the deep inelastic scattering sum rules, namely the non-polarized and polarized Bjorken sum rules and to the Gross--Llewellyn Smith sum rule. The results for the $D$-function are further applied to estimate the $O(α_s^4)$ QCD corrections to the Minkowskian quantities $R(s) = σ_{tot} (e^{+}e^{-} \to {\rm hadrons}) / σ(e^{+}e^{-} \to μ^{+} μ^{-})$ and $R_τ = Γ(τ\to ν_τ + {\rm hadrons}) / Γ(τ\to ν_τ \overlineν_{e} e)$. The problem of the fixation of the uncertainties due to the $O(α_s^5)$ corrections to the considered quantities is also discussed.

hep-ph↗
arXiv1994

Estimates of the higher-order QCD corrections: Theory and Applications

We consider the further development of the formalism of the estimates of higher-order perturbative corrections in the Euclidean region, which is based on the application of the scheme-invariant methods, namely the principle of minimal sensitivity and the effective charges approach. We present the estimates of the order $O(α^{4}_{s})$ QCD corrections to the Euclidean quantities: the $e^+e^-$-annihilation $D$-function and the deep inelastic scattering sum rules, namely the non-polarized and polarized Bjorken sum rules and to the Gross--Llewellyn Smith sum rule. The results for the $D$-function are further applied to estimate the $O(α_s^4)$ QCD corrections to the Minkowskian quantities $R(s) = σ_{tot} (e^{+}e^{-} \to {\rm hadrons}) / σ(e^{+}e^{-} \to μ^{+} μ^{-})$ and $R_τ = Γ(τ\to ν_τ + {\rm hadrons}) / Γ(τ\to ν_τ \overlineν_{e} e)$. The problem of the fixation of the uncertainties due to the $O(α_s^5)$ corrections to the considered quantities is also discussed.

hep-ph↗
arXiv1994

Estimates of the O(alpha_s^4) corrections to sigma_{tot}(e^+e^- \rightarrow hadrons), Gamma(τ\rightarrow ν_τ +hadrons) and deep inelastic scattering sum rules

We present the estimates of the order $O(α^{4}_{s})$ QCD corrections to $R(s)$, $R_τ$ and to the deep-inelastic scattering sum rules, namely to the non-polarized and polarized Bjorken sum rules and to the Gross-Llewellyn Smith sum rule. The estimates are obtained in the $\overline{MS}$-scheme using the principle of minimal sensitivity and the effective charges approach.

hep-ph↗
arXiv1994

The Ellis-Jaffe Sum Rule: The Estimates of the Next-to-Next-to- Leading-Order QCD Corrections

The procedure of the estimates of the higher-order perturbative QCD corrections to the physical quantities is generalized to the case when the quantities under consideration obey the renormalization group equationts with the corresponding anomalous dimension function. This procedure is used to estimate the $α_s^3$-corrections to the singlet part of the Ellis-Jaffe sum rule for $f=3$ numbers of flavours.

hep-ph↗
arXiv1993

Connections between Deep-Inelastic and Annihilation Processes at Next-to-Next-to-Leading Order and Beyond

We have discovered 7 intimate connections between the published results for the radiative corrections, $\Ck$, to the Gross--Llewellyn Smith (GLS) sum rule, in deep-inelastic lepton scattering, and the radiative corrections, $\Cr$, to the Adler function of the flavour-singlet vector current, in $\ee$ annihilation. These include a surprising relation between the scheme-independent single-electron-loop contributions to the 4-loop QED $β$\/-function and the zero-fermion-loop abelian terms in the 3-loop GLS sum rule. The combined effect of all 7 relations is to give the factorization of the 2-loop $β$\/-function in \[\Ds\equiv\Ck\Cr-1=\frac{\Be}{\Aq}\left\{S_1\Cf\Aq+\left[S_2\Tf\Nf +\Sa\Ca+\Sf\Cf\right]\Cf\Aq^2\right\}+O(\Aq^4)\,,\] where $\Aq=\al(μ^2=Q^2)/4π$ is the $\MS$ coupling of an arbitrary colour gauge theory, and \[S_1=-\Df{21}{2}+12\Ze3\,;\quad S_2=\Df{326}{3}-\Df{304}{3}\Ze3\,;\quad \Sa=-\Df{629}{2}+\Df{884}{3}\Ze3\,;\quad \Sf=\Df{397}{6}+136\Ze3-240\Ze5\] specify the sole content of $\Ck$ that is not already encoded in $\Cr$ and $\Be=Q^2\rd\Aq/\rd Q^2$ at $O(\Aq^3)$. The same result is obtained by combining the radiative corrections to Bjorken's polarized sum rule with those for the Adler function of the non-singlet axial current. We suggest possible origins of $β$ in the `Crewther discrepancy', $\Ds$, and determine $\Ds/(\Be/\Aq)$, to all orders in $\Nf\Aq$, in the large-$\Nf$ limit, obtaining the {\em entire\/} series of coefficients of which $S_1$ and $S_2$ are merely the first two members.

hep-ph↗
arXiv1993

The Effects of the Massless O(alpha_s^2), O(αα_s), O(α^2) QCD and QED Corrections and of the Massive Contributions to Gamma(H^0\rightarrow b\overline{b})

We consider in detail various theoretical uncertainties of the perturbative predictions for the decay width of $H^0\rightarrow b\overline{b}$ process in the region $50\ GeV< M_H\leq 2M_W$. We calculate the order $O(α_s^2)$-contributions to the expression for $Γ_{Hb\overline{b}}$ through the pole quark mass and demonstrate that they are important for the elimination of the numerical difference between the corresponding expression and the one through the running $b$-quark mass. The order $O(αα_s)$ and $O(α^2)$ massless and order $O(m_b^2/M_H^2)$ massive corrections to $Γ_{Hb\overline{b}}$ are also calculated. The importance of the latter contributions for modeling of the threshold effects is demonstrated. The troubles with identifying of the 4 recent L3 events $e^+e^-\rightarrow l^+l^-γγ$ with the decay of a Standard Higgs boson are discussed.

hep-ph↗
arXiv1992

Analytical on-shell QED results: 3-loop vacuum polarization, 4-loop beta-function and the muon anomaly

We present the results of analytical calculations of the 3-loop contributions to the asymptotic photon vacuum polarization function, in the on shell scheme, and of the 4-loop contributions to the on shell QED beta-function. These are used to evaluate various 4-loop and 5-loop contributions to the muon anomaly. Our analytical contributions to (g-2)_μdiffer significantly from previous numerical results. A very recent numerical re-evaluation of 4-loop muon-anomaly contributions has yielded results much closer to ours.

hep-ph↗