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We perform a global fit of parton distribution functions (PDFs) together with the strong coupling constant αs and the quark masses mc, mb and mt at next-to-leading order (NLO) in QCD. The analysis applies the MS¯ renormalization scheme for αs and all quark masses. It is performed in the fixed-flavor number scheme for nf=3,4,5 and uses the same data as the previous ABMP16 fit at next-to-next-to-leading order (NNLO). The new NLO PDFs complement the set of ABMP16 PDFs and are to be used consistently with NLO QCD predictions for hard scattering processes. At NLO we obtain the value αs(nf=5)(MZ)=0.1191±0.0011 compared to αs(nf=5)(MZ)=0.1147±0.0008 at NNLO.

We study the impact of state-of-the-art top-quark data collected at the large hadron collider on parton distribution functions (PDFs). Following the ABMP methodology, the fit extracts simultaneously proton PDFs, the strong coupling α s ( M Z ) and heavy-quark masses at next-to-next-to-leading order (NNLO) accuracy in QCD. It includes recent high-statistics data on absolute total inclusive cross sections for    t t ¯ + X , the sum of ( t + X ) and ( t ¯ + X ) hadroproduction, and normalized inclusive data double-differential in the invariant mass and rapidity of the t t ¯ pair at S = 13  TeV. The gluon PDF at large x and the top-quark mass value derived from these data are well compatible with the previous ABMP16 results, but with significantly smaller uncertainties, reduced by up to a factor of two. At NNLO in QCD we obtain for the strong coupling the value α s ( n f = 5 ) ( M Z ) = 0.1150 ± 0.0009 and for the top-quark mass in the MS ¯ -scheme m t ( m t ) = 160.6 ± 0.6  GeV, corresponding to m t pole = 170.2 ± 0.7  GeV in the on-shell scheme. The new fit, dubbed ABMPtt, is publicly released in grids in LHAPDF format.

A bstract The impact of measurements of heavy-flavour production in deep inelastic ep scattering and in pp collisions on parton distribution functions is studied in a QCD analysis at next-to-leading order. Recent combined results of inclusive and heavy-flavour produc- tion cross sections in deep inelastic scattering at HERA are investigated together with heavy-flavour production measurements at the LHC. Differential cross sections of charm- and beauty-hadron production measured by the LHCb collaboration at the centre-of-mass energies of 5, 7 and 13 TeV as well as the recent measurements of the ALICE experiment at the centre-of-mass energies of 5 and 7 TeV are explored. These data impose additional constraints on the gluon and the sea-quark distributions at low partonic fractions x of the proton momentum, down to x ≈ 10 − 6 . The impact of the resulting parton distribution function in the predictions for the prompt atmospheric-neutrino fluxes is studied.

We evaluate the impact of recent SeaQuest (FNAL-E906 experiment) data on dimuon production in proton-deuteron and proton-proton collisions on parton distribution functions (PDFs). We find these data in a good agreement with the QCD predictions based on PDFs fitted to the Tevatron and LHC data on forward production of W and Z bosons. As a basis for this study we use the ABMP16 PDF fits and show that they turn out to be compatible with the SeaQuest data, and that these data have constraining power, allowing to reduce the uncertainties on the isospin asymmetry of the light-sea-quark distribution at large longitudinal momentum fraction x . We discuss the nuclear corrections needed to describe the deuteron and show that they affect the theoretical description of the proton-deuteron Drell–Yan cross section at the level of O ( 0.5 - 1 ) %. We also comment on the compatibility of the SeaQuest results with other state-of-the-art PDF fits and show that these data are in clear disagreement with models proposing an SU(3)-flavor symmetric quark sea. Finally, we perform a comparison between the second Mellin moments of the light-quark PDFs and recent results from various lattice QCD computations, which demonstrates good compatibility, albeit limited by the uncertainties inherent in current lattice QCD simulations.

We present a detailed comparison of the fixed-order predictions computed by four publicly available computer codes for Drell–Yan processes at the LHC and Tevatron colliders. We point out that while there is agreement among the predictions at the next-to-leading order accuracy, the predictions at the next-to-next-to-leading order (NNLO) differ, whose extent depends on the observable. The sizes of the differences in general are at least similar, sometimes larger than the sizes of the NNLO corrections themselves. We demonstrate that the neglected power corrections by the codes that use global slicing methods for the regularization of double real emissions can be the source of the differences. Depending on the fiducial cuts, those power corrections become linear, hence enhanced as compared to quadratic ones that are considered standard.

A bstract We present a comprehensive study of high-energy double logarithms in inclusive DIS. They appear parametrically as α s n ln 2 n−k x at the n -th order in perturbation theory in the splitting functions for the parton evolution and the coefficient functions for the hard scattering process, and represent the leading corrections at small x in the flavour non-singlet case. We perform their resummation, in terms of modified Bessel functions, to all orders in full QCD up to NNLL accuracy, and partly to N 3 LL and beyond in the large- n c limit, and provide fixed-order expansions up to five loops. In the flavour-singlet sector, where these double logarithms are sub-dominant at small x compared to single-logarithmic α s n x − 1 ln n−k x BFKL contributions, we construct fixed-order expansions up to five loops at NNLL accuracy in full QCD. The results elucidate the analytic small- x structure underlying inclusive DIS results in fixed-order perturbation theory and provide important information for present and future numerical and analytic calculations of these quantities.

A bstract We extract the top-quark mass value in the on-shell renormalization scheme from the comparison of theoretical predictions for pp → t t ¯ + X at next-to-next-to-leading order (NNLO) QCD accuracy with experimental data collected by the ATLAS and CMS collaborations for absolute total, normalized single-differential and double-differential cross-sections during Run 1, Run 2 and the ongoing Run 3 at the Large Hadron Collider (LHC). For the theory computations of heavy-quark pair-production we use the MATRIX framework, interfaced to PineAPPL for the generation of grids of theory predictions, which can be efficiently used a-posteriori during the fit, performed within xFitter. We take several state-of-the-art parton distribution functions (PDFs) as input for the fit and evaluate their associated uncertainties, as well as the uncertainties arising from renormalization and factorization scale variation. Fit uncertainties related to the datasets are also part of the extracted uncertainty of the top-quark mass and turn out to be of similar size as the combined scale and PDF uncertainty. Fit results from different PDF sets agree among each other within 1 σ uncertainty, whereas some datasets related to t t ¯ decay in different channels (dileptonic vs. semileptonic) point towards top-quark mass values in slight tension among each other, although still compatible within 2 . 5 σ accuracy. Our results are compatible with the PDG 2022 top-quark pole-mass value. Our work opens the road towards more complex simultaneous NNLO fits of PDFs, the strong coupling α s ( M Z ) and the top-quark mass, using the currently most precise experimental data on t t ¯ + X total and multi-differential cross sections from the LHC.

A bstract Parton evolution equations in QCD are controlled by the anomalous dimensions of gauge-invariant twist-two spin- N quark and gluon operators. Under renormalization, these mix with gauge-variant operators of the same quantum numbers, referred to as alien operators. Our work addresses the systematic study of these alien operators at arbitrary spin N , using generalized BRST symmetry relations to derive their couplings and Feynman rules at all values of N . We observe how the all- N structure of the generalized (anti-)BRST constraints relates the couplings of alien operators with n + 1 gluons to those with n gluons. Realizing a bootstrap, we present all one-loop results necessary for performing the operator renormalization up to four loops in QCD.

A bstract In perturbation theory, the anomalous dimensions of twist-two operators have poles at negative or small positive integer values of spin and therefore must be resummed at these points. It was observed earlier that a certain quadratic combination of the anomalous dimensions remains finite at the right-most singularities, providing an efficient tool for resummation. In this paper, we analyze the small-spin behavior of the anomalous dimensions for all types of twist-two operators in the O ( N )-symmetric φ 4 model at the four-loop level, in the complex φ 3 model at the three-loop level, and the Gross-Neveu-Yukawa model at the two-loop level. We find that the behavior of the anomalous dimensions at singular points is consistent with theoretical expectations, and we present expressions for the resummed anomalous dimensions.

We determine the strong coupling from high-energy data for the Drell–Yan process and top-quark hadro-production collected at the Large Hadron Collider and the Tevatron combined with the world data on deep-inelastic scattering (DIS) and fixed-target Drell–Yan data. The theory description uses results at next-to-next-to-leading order in perturbative QCD in the MS ¯ -scheme together with leading order QED evolution. The DIS data are subject to stringent kinematic cuts to suppress the contribution of power corrections. We apply a cut on the hadronic invariant mass squared W 2 ≥ 12.5 GeV 2 together with a series of cuts on momentum transfer squared Q 2 . Discarding higher-twist terms we find that the value of strong coupling α s ( m Z ) preferred by the data stabilizes at large enough cuts on Q 2 , when low- Q 2 DIS data sensitive to power corrections are effectively removed. In particular, we extract the value of α s ( m Z , N f = 5 ) = 0.1152 ± 0.0008 for N f = 5 light flavors with the cut Q 2 > 10 GeV 2 . In the absence of higher-twist terms less tight cuts on Q 2 show a clear deterioration of the fit and lead to rising values of the strong coupling, shifted upwards by about two standard deviations.