Search

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 1σ 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 αs(MZ) 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The hadroproduction of a W boson in association with a charm quark at the Large Hadron Collider is at the centre of current investigations due to its potential to probe the strangeness content of the proton. In this paper we present an implementation of the W + c production process in the PowHel event generator matched to the PYTHIA8 parton shower approach, allowing to obtain predictions for differential cross-sections with NLO QCD accuracy matched to the accuracy of the Shower Monte Carlo event generator. Effects of non-diagonal CKM matrix elements, finite charm quark mass and off-shell W decays including spin correlations are taken into account. We investigate the production of a leptonically decaying W boson in association with either a charmed meson (W± + D∗∓) or a charmed jet (W± + jc) and compare our predictions with particle-level measurements by the ATLAS and CMS collaborations at s = 7 and 13 TeV. The role of the so-called "opposite sign" and "same sign" contributions to the theoretical cross-sections is presented and discussed, pointing out the importance of including parton shower effects for a reliable estimate of the latter and a faithful comparison with experimental data. [ABSTRACT FROM AUTHOR]

We present predictions for heavy-quark production at the Large Hadron Collider making use of the MS ¯ and MSR renormalization schemes for the heavy-quark mass as alternatives to the widely used on-shell renormalization scheme. We compute single and double differential distributions including QCD corrections at next-to-leading order and investigate the renormalization and factorization scale dependence as well as the perturbative convergence in these mass renormalization schemes. The implementation is based on publicly available programs, MCFM and xFitter, extending their capabilities. Our results are applied to extract the top-quark mass using measurements of the total and differential t t ¯ production cross-sections and to investigate constraints on parton distribution functions, especially on the gluon distribution at low x values, from available LHC data on heavy-flavor hadro-production. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]