Search

We present the exact results obtained in [1], which relate the hatted and standard -values and are valid in all orders of perturbation theory. We demonstrate their compact integral representation. The results were obtained using the Landau–Khalatnikov–Fradkin transformation between massless charged particle propagators interacting with gauge fields in two different gauges. A reason for the appearance of hatted -values is not clear and needs to be explained. [ABSTRACT FROM AUTHOR]

The experimental data obtained for the polarized Bjorken sum rule for small values of Q2 are approximated by the predictions obtained in the framework of analytic QCD up to the fifth order perturbation theory, whose coupling constant does not contain the Landau pole. We found an excellent agreement between the experimental data and the predictions of analytic QCD, as well as a strong difference between these data and the results obtained in the framework of perturbative QCD. [ABSTRACT FROM AUTHOR]

We give predictions for the ratio at small values of Bjorken variable x in the first three orders of perturbation theory. We show an approximate x-independence of at low x and non-large values (), irrespectively on the gluon density in a proton used in the calculations. This observation could be useful in subsequent phenomenological studies of the heavy flavor production at future lepton–hadron and hadron–hadron colliders. [ABSTRACT FROM AUTHOR]

We present a nonlinear modification of the evolution of the gluon density, obtained at small x from the Berger-Block-Tan form of the deep inelastic structure function F2 in the leading order of perturbation theory. [ABSTRACT FROM AUTHOR]

An exact formula that relates standard functions and so-called hatted () functions in all orders of perturbation theory is presented. This formula is based on the Landau–Khalatnikov–Fradkin transformation. [ABSTRACT FROM AUTHOR]

We investigate the polarized Bjorken sum rule (BSR) in three approaches to QCD with analytic (holomorphic) coupling: Analytic Perturbation Theory (APT), Two-delta analytic QCD (2anQCD) and Three-delta lattice-motivated analytic QCD in the three-loop and four-loop MOM scheme (3l3anQCD, 4l3anQCD). These couplings do not have unphysical (Landau) singularities, and have finite values when the transferred momentum goes to zero, which allows us to explore the infrared regime. With the exception of APT, these theories at high momenta practically coincide with the underlying perturbative QCD (pQCD) in the same scheme. We apply them in order to verify the Bjorken sum rule within the range of energies available in the data collected by the experimental JLAB collaboration, i.e. and compare the results with those obtained by using the perturbative QCD coupling. The results of the new frameworks with respective couplings (2 and 3) are in good agreement with the experimental data for already when only one higher-twist term is used. In the low- regime , we use PT-motivated expression or an expression motivated by the light-front holography (LFH) QCD used earlier in the literature. [ABSTRACT FROM AUTHOR]

We present results for the universal anomalous dimension γuni( j) of Wilson twist-2 operators in the $$ \mathcal{N} $$ = 4 supersymmetric Yang-Mills theory in the first four orders of perturbation theory. [ABSTRACT FROM AUTHOR]

Experimental data obtained for the polarized Bjorken sum rule (BSR) Γ1p-n(Q2) are fitted by using predictions derived within a truncated operator product expansion (OPE) approach to QCD. Four QCD versions are considered: perturbative QCD (pQCD) in the MS¯ scheme, Analytic Perturbation Theory (APT), and 2δ and 3δ analytic QCD versions. In contrast to pQCD, these QCD variants do not have Landau singularities at low positive Q2, which facilitates the fitting procedure significantly. The fitting procedure is applied first to the experimental data of the inelastic part of BSR, and the known elastic contributions are added after the fitting. In general, when 2δ and 3δ QCD coupling is used the fitted curves give the best results, within the Q2-range of the fit as well as in extended Q2-intervals. When the fitting procedure is applied to the total BSR, i.e., to the sum of the experimental data and the elastic contribution, the quality of the results deteriorates significantly. [ABSTRACT FROM AUTHOR]

Abstract: In this Letter we evaluate Wilson coefficients for “deep inelastic scattering” (DIS) in SYM theory at NLO in perturbation theory, using as a probe an R-symmetry conserved current. They exhibit uniform transcendentality and coincide with the piece of highest transcendentality in the corresponding QCD Wilson coefficients. We extract from the QCD result a NNLO prediction for the SYM Wilson coefficient, and comment on the features of its Regge limit asymptotics. [Copyright &y& Elsevier]

We present a new approach to consider and include both the perturbative and the nonperturbative contributions to the multiplicities of gluon and quark jets. Thanks to this new method, we have included for the first time new contributions to these quantities obtaining next-to-next-to-leading-logarithmic resummed formulas. Our analytic expressions depend on two nonperturbative parameters with a clear and simple physical interpretation. A global fit of these two quantities shows how our results solve a long- standing discrepancy in the theoretical description of the data. [ABSTRACT FROM AUTHOR]