I report on the progress in the precision studies of hadronic parton distributions by the CTEQ-TEA (Tung Et Al.) group.
In this talk we will summarise the latest updates to PDF fits using the MSHT
approach. This will include details of high-x PDF sensitivity to jet/dijet
data, Z boson transverse distributions and high x data providing information
on quark flavours. We will also discuss the most recent determinations of
the strong coupling constant at both NNLO and N^3LO in perturbation theory.
We will...
I present recent progress in the framework of the NNPDF global PDF analyses. These include a determination of proton structure at aN3LO accuracy and the assessment of its implications for N3LO cross-sections at the LHC; NNPDF4.0 variants with QED effects and missing higher order uncertainties accounted for; the intrinsic valence charm content of the proton; selected methodological studies; and...
We investigate the impact of recent LHC measurements of differential top-quark pair production cross sections on the proton parton distribution functions (PDFs) using the ABMP16 methodology. The theoretical predictions are computed at NNLO QCD using the state-of-the-art MATRIX framework. The top-quark mass and strong coupling constants are free parameters of the fit, and we pay particular...
We present recent updates in the xFitter software framework for global fits of parton distribution functions (PDFs) in high-energy physics. Our focus is on investigating the sensitivity to Z boson couplings using the forward-backward asymmetry in Drell-Yan production. By utilizing an effective approach and simulated data, we assess the accuracy of these couplings, specifically considering the...
In recent years, precision in PDF determinations has significantly improved due to a combination of experimental (better statistics, control over uncertainties) and theoretical improvements (NNLO predictions, N3LO splitting functions). Thanks to this enhanced precision,
differences in the methodologies, data treatment and theory choices can now be resolved between different fitting...
We study the impact of new data sets on the NNPDF4.0 PDF determination. Specifically, we consider measurements for processes that are sensitive to the gluon PDF: legacy H1 and ZEUS DIS + jet and DIS + dijet production and Run II ATLAS and CMS single-inclusive jet, dijet, and top pair production. We take into account theory uncertainties in PDF evolution and in the cross-section matrix...
Recent measurements of jet cross sections in proton-proton collisions with the CMS experiment are presented. The measured jet cross sections are corrected for detector effects and compared with the predictions from perturbative QCD, and exploited to derive constraints on parton distribution functions and to mesure alpha_S.
Nucleon structure functions, as measured in lepton-nucleon scattering, have historically provided a critical observable in the study of partonic dynamics within the nucleon. However, at very large parton momenta it is experimentally and theoretically challenging to extract parton distributions due to the onset of non-perturbative contributions. New results will be presented from experiment...
The available world deep-inelastic scattering data on the proton and deuteron structure functions F2p and F2d, and the ratio F2p/F2d, were leveraged to extract the free neutron structure function, F2n, and associated uncertainties using the latest nuclear effects calculations with the deuteron data. Special attention was devoted to the normalization of the proton and deuteron experimental...
Proton-proton collisions at the LHC generate a high-intensity collimated beam of neutrinos in the forward (beam) direction, characterised by energies of up to several TeV. The recent observation of LHC neutrinos by FASERν and SND@LHC signals that this hitherto ignored particle beam is now available for scientific inquiry. Here we quantify the impact that neutrino deep-inelastic scattering...
We present a next-to-leading order perturbative QCD calculation of dimuon production in neutrino-nucleus collisions. This process is vital in the determination of the strange and anti-strange quark distributions in global PDF analyses. It is usually calculated by assuming factorization to the inclusive DIS charm production cross section, with a multiplicative acceptance correction to account...
The goal of FASER, the ForwArd Search ExpeRiment, at the CERN LHC, is to investigate light, weakly-interacting particles. Aligned with the collision axis line-of-sight of the ATLAS interaction point, it is located $480$ m downstream, and covers the previously unexplored pseudorapidity range of $\eta > 8.8$. Sitting in front of the main electronic detector, the passive FASER$\nu$ neutrino...
SND@LHC started taking data at the beginning of Run 3 of the LHC. The experiment is designed to perform measurements with neutrinos produced in proton-proton collisions at the LHC in an energy range between 100 GeV and 1 TeV. It covers a previously unexplored pseudo-rapidity range of 7.2 < η < 8.4. The detector is located 480 m downstream of the ATLAS interaction point in the TI18 tunnel. The...
Distribution amplitudes are functions of non-perturbative matrix elements describing the hadronization of an initial set of quarks and gluons. They are the crossed-channel analogs of the more commonly known parton distribution functions, which describe the longitudinal momentum distribution inside a hadron. Thanks to factorization theorems, they can be used to compute the scattering amplitude...
The formalism of short-distance factorization, conveyed through the pseudo-distribution approach, allows for the extraction of lightcone correlators from field theories formulated on Euclidean geometries. Thus, within this formalism, the extraction of parton distributions from Lattice-QCD becomes feasible. In this work we take advantage of the pseudo-distribution idea to compute, for the first...
The four-loop DGLAP splitting functions, which govern the scale evolution of the Parton Distribution Functions (PDFs), are of the missing ingredients to push the frontier of QCD calculations to N3LO accuracy, as required to match the experimental precision at the LHC and at the forthcoming EIC. In this talk, I will report on the recent progress in the determination of the splitting functions...
The general mass variable flavor number (GMVFN) scheme S-ACOT-MPS will
be discussed for proton-proton collisions. The impact of heavy-flavor
contributions within this factorization scheme will be shown for the production of a $Z$ boson in association with a charm/bottom quark in pQCD. An amended version of the QCD factorization formula for proton-proton collisions will be discussed as well...
A new measurement of inclusive-jet cross sections in the Breit frame in neutral current deep inelastic scattering using the ZEUS detector at the HERA collider is presented. The data were taken in the years 2004–2007 at a centre-of-mass energy of 318 GeV and correspond to an integrated luminosity of 347 pb$^{-1}$. The jets were reconstructed using the $k_T$-algorithm in the Breit reference...
The H1 Collaboration reports the first measurement of the 1-jettiness event shape observable $\tau_{1}^{b}$ in neutral-current deep-inelastic electron-proton scattering. The analysis is based on data recorded in 2003-2007 by the H1 detector at the HERA collider for ep collisions at $\sqrt{s}=319$ GeV, with integrated luminosity of 351.1 pb$^{-1}$. The observable $\tau_{1}^{b}$ is equivalent to...
The energy-energy correlator(EEC) is an event shape observable that probes the angular correlations of energy depositions in detectors at high-energy collider facilities. It has been investigated extensively in the context of precision QCD. In this talk, I will present our recent works on the energy-energy correlator in DIS. In the back-to-back limit, the observable we propose is sensitive to...
We perform a simultaneous global analysis of hadron fragmentation functions (FFs) to various charged hadrons at next-to-leading order in QCD. The world data set includes results from electron-positron single-inclusive annihilation, semi-inclusive deep inelastic scattering, as well as proton-proton collisions including jet fragmentation measurements which lead to strong constraints on the gluon...
In this talk I will re-examine the definition of PDF errors within the MSHT framework. This is a key issue in light of LHC high precision requirements that must be addressed if we are to provide accurate as well as precise PDF determinations. I will in particular examine the role of the tolerance and the question of parameterisation flexibility and bias, and comment on the implications of this...
This study presents a novel methodology for estimating uncertainty intervals in fits of Parton Distribution Functions (PDFs). By combining toy examples and fitting real-world PDFs, we critically evaluate the robustness of the Monte-Carlo (MC) replica method and the Hessian method in estimating credible intervals for PDFs. Our findings reveal that the methodologies typically used in PDF fits...
As experimental data is becoming more precise, understanding the impact of the uncertainties in the errors, especially the systematic errors, is increasingly becoming a significant focus of PDF groups. In this talk we will explain how the error on errors can be modelled and how this framework can be applied to both uncorrelated and correlated systematic errors, and discuss the potential...
We discuss a Bayesian methodology for the solution of the inverse problem underlying the determination of parton distribution functions (PDFs). In our approach, Gaussian Processes (GPs) are used to model the PDF prior, while Bayes’ theorem is used in order to determine the posterior distribution of the PDFs given a set of data. We discuss the general formalism, the Bayesian inference at the...
The current scientific standard in PDF uncertainty estimation relies either on repeated fits over artificially generated data to arrive at Monte Carlo samples of best fits or on the Hessian method, which uses a quadratic expansion of the figure of merit, the $\chi^2$-function. Markov chain Monte Carlo methods allows one to access the uncertainties of PDFs without making use of quadratic...
We discuss the preliminary results of our new global nuclear PDF analysis that combines a number of our previous improvements into one consistent framework with updates to the underlying theoretical treatment as well as the addition of new available data. In particular, the new global analysis will be the first to include neutrino DIS scattering data together with JLab high-$x$ DIS data and...
Nuclear Parton Distribution Functions (nPDFs) are crucial for understanding nuclear structure and for providing predictions for heavy-ion collisions. nPDFs have been determined via ‘global QCD analyses’, which is a statistical approach based on performing a fit of nPDF-dependent theoretical predictions to the relevant experimental data. One of the crucial aspects of nPDF determination is the...
Deeply inelastic scattering (DIS) of a high-energy leptons ($\ell$ or $\nu$) off hadronic targets remains an incredibly powerful probe of both hadronic substructure and leptonic couplings to matter. As current and near-future experiments will investigate DIS kinematics at large Bjorken $x$ and small momentum transfers to unrivaled precision on a variety of nuclei, it remains crucial that...
We study the systematic uncertainty and possible biases introduced by theoretical assumptions needed to include DIS data at large x in a global QCD analysis. In particular, working in the CTEQ-JLab framework, we focus on different implementations of higher-twist corrections to the nucleon structure functions, and of off-shell deformations of PDF in deuteron targets, and how their interplay...
We study nuclear DIS basing on a microscopic model [1], which addresses a number of nuclear corrections arising from energy-momentum spectrum of bound nucleons, off-shell modification of bound nucleon structure functions, corrections from meson-exchange currents, focusing on the region of large Brorken x and the light nuclei with two and three bound nucleons, for which the energy-momentum...
Results published in 1983 by the European Muon Collaboration (EMC) at CERN suggested that a nucleon's partonic structure is modified when multiple nucleons are bound together in the nuclear environment. This phenomenon, now known as the EMC Effect, came as a surprise due to the relatively small energies involved in nucleon-nucleon interactions when compared to the energies present in DIS...
New preliminary results from COMPASS on pion and kaon multiplicities in Semi-Inclusive Deep Inelastic Scattering on a proton target are presented. These proton findings serve as a complementary dataset to the deuteron results published in 2017. In this updated analysis, we have implemented an enhanced treatment of Radiative Corrections using DJANGOH MC. A comparison with the previously...
In light of recent progress on both the experimental and lattice-QCD sides, our understanding of the pion’s structure has evolved. Phenomenological, or global, QCD analyses — the focus of this talk— play a crucial role in establishing a bridge between experimental data, theoretical predictions, and lattice-QCD studies. I will present recent efforts in the determination of the distribution of...
We present an analysis to extract kaon parton distribution functions (PDFs) using meson-induced Drell-Yan and quarkonium production data. Starting from the statistical model, first developed for describing the partonic structure of nucleons and later applied to the pion, we have extended this approach to perform a global fit to existing kaon-induced Drell-Yan and charmonium production data....
We present a systematic quantum algorithm, which integrates both the hadronic state preparation and the evaluation of real-time light-front correlators, to study parton distribution function (PDF) and light cone distribution amplitude (LCDA). As a proof of concept, we demonstrate the first direct simulation of the PDF and LCDA in the 1+1 dimensional Nambu-Jona-Lasinio model. We show the...
We introduce our novel Bayesian parton density determination code, \partondensity. The motivation for this new code, the framework and its validation are described. As we show, \partondensity provides both a flexible environment for the determination of parton densities and a wealth of information concerning the knowledge update provided by the analyzed data set.
The energy dependence for the singlet sector of Parton Distributions Functions (PDFs) is described by an entangled pair of ordinary linear differential equations. Although there are no closed analytic solutions, it is possible to provide approximated results depending on the assumptions and the methodology adopted. These results differ in their sub-leading, neglected terms and ultimately they...
The increasingly precise experimental data from LHC have led to global extractions of parton distribution functions with significantly improved accuracy. While there are ways to approximate some theoretical uncertainties like those arising from the choices of the factorization scale, alternative approaches to tame the remaining theoretical uncertainties may eventually be needed for precision...
Splitting functions, often referred to as the DGLAP evolution kernel, control the scale evolution of parton distribution functions. A highly effective approach for computing these splitting functions involves the use of off-shell operator matrix elements. Nonetheless, complications arise in the singlet sector, where physical operators become entangled with non-physical ones, giving rise to...
We discuss the current staus of PDFs at NLO in perturbation theory, making comparisons with NNLO and between groups, and also summariusing the current status of the remaining uncertainty at NLO.In particular we show the result of a recent benchmarking study of PDF evolution between groups.
With a large momentum transfer, high energy lepton-hadron scattering induces both QED and QCD radiations. Contribution of induced QCD radiation to scattering cross sections has been consistently evaluated in terms of QCD factorization approach, while contribution from induced QED radiation has been historically corrected by imposing a “radiative correction factor” to the lowest order (LO)...
The Parton Branching (PB) method outlines the evolution of transverse momentum-dependent (TMD) parton distributions across various kinematic regions, ranging from small to large transverse momenta $k_T$. In the small $k_T$ region, the PB method is highly sensitive to both the intrinsic motion of partons (intrinsic $k_T$) and the resummation of soft gluons, as described by the PB TMD evolution...
