Conveners
WG1: Structure Functions and Parton Densities: Parallel session 1
- TIMOTHY J HOBBS (Argonne National Laboratory)
WG1: Structure Functions and Parton Densities: Parallel session 2
- Mateusz Dyndal (AGH University of Krakow)
WG1: Structure Functions and Parton Densities: Parallel session 3
- Chiara Bissolotti (Argonne National Laboratory)
WG1: Structure Functions and Parton Densities: Parallel session 5
- Tanjona R. Rabemananjara (NIKHEF & VU Amsterdam)
WG1: Structure Functions and Parton Densities: Parallel session 6
- Claire Gwenlan (University of Oxford (GB))
WG1: Structure Functions and Parton Densities: Parallel session 7
- Mpho Gift Doctor Gololo (University of Johannesburg (ZA))
In this talk, I will show how ambiguities related to solutions of renormalisation group equations (RGEs) can contribute significantly to systematic uncertainties of theoretical predictions for physical observables. I will discuss a general method to estimate these systematic effects using techniques inspired by soft-gluon and transverse-momentum resummation approaches. As application cases, I...
The LHC generates a beam of high-energy neutrinos in the forward direction, whose scientific potential has been ignored in the past. The FASERv and SND@LHC experiments have recently measured signals from these LHC neutrinos for the first time. To produce accurate predictions including NLO QCD corrections for FASER$\nu$ and SND@LHC and the planned experiments at the proposed Forward Physics...
We present an update to our SIDIS-based approach for dimuon production in neutrino-nucleus collisions [1]. Dimuon production, an important constraint for the strange-quark distribution in global analyses of both proton and nuclear parton distributions, has traditionally been calculated by assuming factorization to the inclusive DIS charm production process. In our approach, we forego this...
Mass-dependent quark contributions are of great importance to DIS processes. The simplified-ACOT-$\chi$ scheme includes these effects over a wide range of momentum transfers up to next-to-leading order in QCD. In recent years an improvement in the case of neutral current DIS has been achieved by using zero-mass contributions up to next-to-next-to-leading order (NNLO) with massive phase-space...
I present updates related to the parton distribution functions (PDFs) obtained using the MSHT approach. I address inclusion of new data types, e.g. LHC dijet data, studies of strong coupling dependence and determinations, and closure tests and comparison to the neural network approach and implications for best fits and uncertainties.
We study the impact of state-of-the-art top-quark data collected at the Large Hadron Collider (LHC) on proton parton distribution functions (PDFs) using the ABMP16 methodology. 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 reduced uncertainties by up to a factor of two. We discuss the...
We summarize latest developments in the CTEQ-TEA global QCD analysis of parton distributions in the nucleon.
We report on recent advancements in the global determination of the unpolarised proton PDFs by the NNPDF collaboration. Since the previous major release, several improvements have been made in both theoretical frameworks and methodological approaches, supplemented with high-statistic measurements from LHC Run II. On the theoretical front, we present the current state-of-the-art PDF...
We investigate the impact of recently computed N3LO corrections to QCD splitting and DIS coefficient functions on global fits of parton distribution functions (PDFs) using the xFitter framework. By comparing fits performed at different perturbative orders, we analyze the modifications introduced to PDFs and their associated uncertainties, incorporating correlated experimental errors....
We will discuss several key updates to the MSHT approximate N3LO PDFs; including the combination of these aN3LO QCD PDFs with QED effects, the first determination of the strong coupling constant at aN3LO, and further updates based on new theoretical information available at N3LO including more precise splitting functions for N3LO PDF evolution. All of this work has important consequences for...
The strong coupling $\alpha_s(Q^2)$ represents one of the fundamental parameters of the Standard Model, and its precise determination is required a variety of phenomenological applications. We present an updated determination of $\alpha_s(m_Z)$ from the global NNPDF4.0 analysis carried out at approximated N$^3$LO (aN$^3$LO) accuracy, which also accounts for NLO QED corrections and the photon...
We discuss how the two existing approximate N3LO (aN3LO) sets of parton distributions (PDFs) from the MSHT20 and NNPDF4.0 series can be combined for LHC phenomenology, both in the pure QCD case and for the QCD⊗QED sets that include the photon PDF. Using the resulting combinations, we present predictions for the total inclusive cross-section for Higgs production in gluon fusion, vector boson...
There have been rapid developments in the direct calculation in lattice QCD (LQCD) of the Bjorken-$x$ dependence of hadron structure through large-momentum effective theory (LaMET) and other similar effective approaches. These methods overcome the previous limitation of LQCD to moments (that is, integrals over Bjorken-$x$) of hadron structure, allowing LQCD to directly provide the kinematic...
We investigate the systematic uncertainties and potential biases arising from the inclusion of large-$x$ corrections to proton and deuteron DIS data in global QCD analyses. Using the CTEQ-JLab framework, we examine various approaches to implementing higher-twist corrections in nucleon structure functions and off-shell PDF modifications in deuteron targets. We analyze how these components...
Fantômas is a C++ module implemented in xFitter for universal approximation of parton densities and other quantum correlator functions using Bézier curves. We review its operating principles and an application of the Fantômas framework to obtain parton distributions in a charged pion with detailed estimates of parametrization and nuclear uncertainties.
In this talk we will critically assess the robustness of uncertainties on parton distribution functions (PDFs) determined using neural networks from global sets of experimental data collected from multiple experiments. The determination of PDFs is an inverse problem, and we study the way the neural network model tackles it when inconsistencies between input datasets are present. We use a...
I will analyse the theoretical uncertainties inherent in the determination of the strong coupling from the transverse momentum (pT) spectrum of the Z boson. Such analyses require fine control of percent-level theoretical effects in small pT region, not only in terms of their magnitude but also of their shape and that of the corresponding theoretical uncertainties. This is theoretically...
Accurately propagating uncertainties is essential for parton distribution functions (PDFs), particularly with the high-precision data expected from the HL-LHC. Traditional methodologies often struggle with strong non-linear dependencies in parameters, underscoring the need for innovative approaches. In this talk, we introduce Colibri, a flexible Bayesian analysis framework for PDFs, enabling...
We present a new global analysis of nuclear PDFs in the nCTEQ approach. Building on a modern proton baseline without nuclear data and extending the kinematic range, we combine and update previous separate analyses that focused on JLab neutral-current DIS, neutrino DIS and dimuon production, and the currently available LHC data, in particular on W/Z-boson and heavy-quark production. For the...
Within the nCTEQ collaboration, we have developed a novel nuclear parton distribution function (nPDF) framework inspired by Short-Range Correlations (SRCs) to bridge the nuclear and particle physics descriptions of nuclei. Initial investigations show that this SRC-based approach yields improved fits as compared to traditional methods, suggesting it may better capture nuclear properties....
The study of hadronization—the process by which quarks and gluons transition into hadrons—is fundamental to understanding the strong interaction dynamics within quantum chromodynamics (QCD). Using the CLAS12 detector at Jefferson Lab, the Run Group E (RGE) experiment offers unprecedented insights into hadronization in the nuclear medium. This talk will present preliminary results from the...
With the LHC transitioning to a precision measurement machine, the proton Parton Distribution Functions (PDFs) are becoming a leading source of uncertainty in analyses such as the measurements of top quark mass or the Higgs boson width. Furthermore, the high-momentum-fraction (high-x) regime is of particular interest when probing the most energetic collisions at the LHC. Thus, it is crucial to...
We study the internal structure of the deuteron at the level of its partons using the basis light-front quantization approach. The Hamiltonian is constructed by incorporating the fundamental QCD interactions arising from the six-quarks and six-quarks-gluon Fock components. We examine the deuteron’s electromagnetic form factors, parton distribution functions, and tensor-polarized properties....
Basis light-front quantization (BLFQ) is a fully relativistic, nonperturbative approach that employs a light-front quantized Hamiltonian with Quantum Chromodynamics (QCD) inputs, aiming for first-principles calculations. For QCD applications in limited Fock space of the nucleon, we incorporate effective confinement into the Hamiltonian, achieving results consistent with global fits and...
