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Register a new userAbout QCD coupling constant at NNLO from DIS data
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We give a brief review of our recent QCD analysis carried out over the deep inelastic scattering data on F2 structure function and in the non-singlet approximation to the accuracy up to next-to-next-to-leading-order. Specifically, analysis was performed over high statistics deep inelastic scattering data provided by BCDMS, SLAC, NMC and BFP collaborations. For the coupling constant the following value alpha_s(M_Z^2) = 0.1167 pm 0.0022 was found.
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Deep inelastic scattering data on F2 structure function from various fixed-target experiments were analyzed in the non-singlet approximation with a next-to-next-to-leading-order accuracy. The study of high statistics deep inelastic scattering data provided by BCDMS, SLAC, NMC and BFP collaborations was carried out separately for the first one and the rest, followed by a combined analysis done as well. For the coupling constant the following value alpha_s(M_Z^2) = 0.1167 +/- 0.0021 (total exp.error) +0.0056/-0.0036(theor) was found, which in this approximation turns out to be slightly less than that obtained at the next-to-leading-order, as was generally anticipated. Ditto the theoretical uncertainties reduced with respect to those obtained in the case of the next-to-leading-order analysis thus confirming earlier observations.
We work out the method for evaluating the QCD coupling constant at finite temperature ($T$) by making use of the finite $T$ renormalization group equation up to the one-loop order on the basis of the background field method with the imaginary time formalism. The background field method, which maintains the explicit gauge invariance, provides notorious simplifications since one has to calculate only the renormalization constant of the background field gluon propagator. The results for the evolution of the QCD coupling constant at finite $T$ reproduce partially the ones obtained in the literature. We discuss, in particular, the origin of the discrepancies between different calculations, such as the choice of gauge, the break-down of Lorentz invariance, imaginary versus real time formalism and the applicability of the Ward identities at finite $T$.
This talk covers three contributions from H1: Measurement of the inclusive e^pm p scattering cross section at high inelasticity y and of the structure function F_L, Determination of the integrated luminosity at HERA using elastic QED Compton events and Inclusive deep inelastic scattering at high Q2 with longitudinally polarized lepton beams at HERA. These are new measurements mainly based on the full HREA-II data but include also those from HERA-I in the combination whenever it is relevant. The main results of these measurements are briefly summarized here.
We present next-to-next-to-leading-order (NNLO) QCD corrections to the production of three isolated photons in hadronic collisions at the fully differential level. We employ qT subtraction within MATRIX and an efficient implementation of analytic two-loop amplitudes in the leading-colour approximation to achieve the first on-the-fly calculation for this process at NNLO accuracy. Numerical results are presented for proton-proton collisions at energies ranging from 7 TeV to 100 TeV. We find full agreement with the 8 TeV results of arXiv:1911.00479 and confirm that NNLO corrections are indispensable to describe ATLAS 8 TeV data. In addition, we demonstrate the significance of NNLO corrections for future precision studies of triphoton production at higher collision energies.
We present a global fit to the structure function F_2 measured in lepton-proton experiments at small values of Bjorken-x, x< 0.01, for all experimentally available values of Q^2, 0.045< Q^2 < 800 GeV^2, using the Balitsky -Kovchegov equation including running coupling corrections. Using our fits to F_2, we reproduce available data for F_L and perform predictions, parameter-free and completely driven by small-x evolution, to the kinematic range relevant for the LHeC.
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