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arXiv · 2607.19183

Impact of Z-boson transverse-momentum resummation on PDF determination

Juan M. Cruz-Martinez·Emanuele R. Nocera·Luca Rottoli·Paolo Torrielli
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Abstract

We study the impact of small-transverse-momentum resummation for neutral-current Drell-Yan lepton-pair production on the determination of collinear parton distribution functions (PDFs). We focus on measurements of the Z-boson transverse-momentum spectrum performed by ATLAS and CMS at the LHC at centre-of-mass energies of 8 and 13 TeV, and include them in PDF fits based on the NNPDF methodology. Theoretical predictions are computed at next-to-next-to-leading order (NNLO) in perturbative QCD and are supplemented with small-transverse-momentum resummation corrections at next-to-next-to-next-to-leading logarithmic accuracy obtained with RadISH. Missing higher-order uncertainties are accounted for through a theory covariance matrix constructed from renormalisation- and factorisation-scale variations. We first revisit the treatment of the 8 TeV data, replacing the fixed-order predictions used in previous analyses with numerically stable NNLO calculations, and removing the additional numerical uncertainties introduced in earlier fits. We then assess the impact of the 13 TeV measurements, of resummation corrections, and of progressively lowering the minimum cut on the dilepton transverse momentum. We find that resummation improves the description of the Z boson transverse-momentum data and is essential for ensuring the overall consistency of the PDF fits. Nevertheless, it does not conclusively support extending the fitted kinematic region to transverse momenta below a few tens of GeV. The impact of resummation on PDFs is moderate, leading primarily to a stabilisation of the gluon PDF in a kinematic region of relevance for LHC phenomenology. Finally, we comment on the fact that the treatment of correlations among theoretical uncertainties may play a central role in PDF fits to measurements with percent- and sub-percent-level precision.

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Juan M. Cruz-Martinez, Emanuele R. Nocera, Luca Rottoli, Paolo Torrielli. 2026-07-21. Impact of Z-boson transverse-momentum resummation on PDF determination. https://arxiv.org/abs/2607.19183

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