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CT25: Progress toward next-generation PDFs for precision phenomenology at the LHC

A. Ablat, A. Courtoy, S. Dulat, Y. Fu, M. Guzzi, T. J. Hobbs, J. Huston, K. Mohan, P. Nadolsky, M. Ponce-Chavez, D. Stump, K. Xie, C. -P. Yuan

TL;DR

CT25 targets next-generation PDFs by performing a global NNLO fit that includes new LHC data and lattice-QCD constraints; it extends CT18 with Drell-Yan, $t\bar{t}$, and inclusive-jet measurements and a dedicated uncertainty framework. The analysis achieves a simultaneous extraction of $\alpha_s(M_Z)$ and PDFs using multiple parametrizations and a dynamical tolerance, with a final reported value $\alpha_s(M_Z) = 0.1183 \pm 0.00225$, and demonstrates that nonlinear uncertainty terms can enlarge PDF errors relative to linear Hessian estimates. The work investigates partial-$N^3LO$ corrections for key Higgs and vector-boson processes, and finds that inconsistent inclusion of higher orders can shift predictions beyond other systematics. Overall, CT25 promises improved precision for LHC phenomenology and guides future collider analyses through robust uncertainty quantification and lattice-theory synergy.

Abstract

We summarize recent progress toward the next generation of CTEQ-TEA parton distribution functions, CT25, based on a global NNLO analysis that incorporates a significant sample of newly included LHC data. We present a baseline fit within the forthcoming full CT25 fit, which includes new Drell-Yan, top-pair, and inclusive-jet data at 8 and 13 TeV, and exhibits non-trivial pulls on the high-$x$ gluon and the flavor structure of the quark sea. In the context of progress toward CT25, we also summarize several recent and ongoing studies of the interplay between phenomenological PDFs and lattice-QCD calculations, simultaneous extractions of $α_s(M_Z)$ within the CT framework, and an expanded program of uncertainty quantification that treats parametrization dependence as an explicit source of epistemic uncertainty, among other issues. We also briefly highlight CT efforts to understand the effects of partial implementations of N$^3$LO corrections into PDF fits, which include benchmark calculations for Higgs and vector-boson processes. We comment on the implications of recent improvements to the CT analysis for precision phenomenology at the LHC and future facilities.

CT25: Progress toward next-generation PDFs for precision phenomenology at the LHC

TL;DR

CT25 targets next-generation PDFs by performing a global NNLO fit that includes new LHC data and lattice-QCD constraints; it extends CT18 with Drell-Yan, , and inclusive-jet measurements and a dedicated uncertainty framework. The analysis achieves a simultaneous extraction of and PDFs using multiple parametrizations and a dynamical tolerance, with a final reported value , and demonstrates that nonlinear uncertainty terms can enlarge PDF errors relative to linear Hessian estimates. The work investigates partial- corrections for key Higgs and vector-boson processes, and finds that inconsistent inclusion of higher orders can shift predictions beyond other systematics. Overall, CT25 promises improved precision for LHC phenomenology and guides future collider analyses through robust uncertainty quantification and lattice-theory synergy.

Abstract

We summarize recent progress toward the next generation of CTEQ-TEA parton distribution functions, CT25, based on a global NNLO analysis that incorporates a significant sample of newly included LHC data. We present a baseline fit within the forthcoming full CT25 fit, which includes new Drell-Yan, top-pair, and inclusive-jet data at 8 and 13 TeV, and exhibits non-trivial pulls on the high- gluon and the flavor structure of the quark sea. In the context of progress toward CT25, we also summarize several recent and ongoing studies of the interplay between phenomenological PDFs and lattice-QCD calculations, simultaneous extractions of within the CT framework, and an expanded program of uncertainty quantification that treats parametrization dependence as an explicit source of epistemic uncertainty, among other issues. We also briefly highlight CT efforts to understand the effects of partial implementations of NLO corrections into PDF fits, which include benchmark calculations for Higgs and vector-boson processes. We comment on the implications of recent improvements to the CT analysis for precision phenomenology at the LHC and future facilities.
Paper Structure (4 sections, 2 figures)

This paper contains 4 sections, 2 figures.

Table of Contents

  1. Introduction
  2. Recent and ongoing dedicated studies in the CT family
  3. The upcoming CT25 main release
  4. Conclusions and outlook

Figures (2)

  • Figure 1: ( Left) A plot of the $pp\to Z^\prime X$ total cross section vs. $M_{Z^\prime}$ in several recent partial N3LO calculations, including an "NNLO+" prescription, convoluted with several NNLO and aN3LO PDFs; we note "HXSWG aN3LO" refers to the combination set of Ref. Cridge:2024icl. ( Right) $\chi^2(\alpha_s)$ profile from the scan of the preferred CT25 PDF parametrization form and different alternative parametrizations. $\chi^2_0$ represents the $\chi^2$ minimum relative to the best fit.
  • Figure 2: Left: The distribution of $x$ and $\mu$ values of data points in the upcoming CT25 global PDF analysis. We show the newly added data points in CT25 in green, in contrast to the removed ones, shown in red. Points common to both the CT25 and CT18 baselines are represented in blue. Right: Gluon uncertainties from CT25, MSHT20, and NNPDF4.0 error PDF ensembles.