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arXiv · 2511.15657

Fant\^omas: An analysis of parton distributions in a pion with B\'ezier parametrizations

Lucas Kotz·Aurore Courtoy·Pavel Nadolsky·Fredrick Olness·Maximiliano Ponce-Chavez
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Abstract

We systematically explore the parametrization dependence of the Parton Distribution Functions (PDFs) to better quantify the true uncertainty from global QCD analyses. To achieve this, we employ a novel technique that automates the generation of polynomial parametrizations for PDFs using B\'ezier curves. This technique is implemented in a C++ module, named Fant\^omas, which is now included within the xFitter program. As an example, we examine the charged pion PDF. Our analysis reveals that the sea and gluon distributions in the pion are strongly correlated, and PDF solutions featuring a vanishing gluon and a large quark sea are still experimentally allowed.

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Lucas Kotz, Aurore Courtoy, Pavel Nadolsky, Fredrick Olness, Maximiliano Ponce-Chavez. 2025-11-19. Fant\^omas: An analysis of parton distributions in a pion with B\'ezier parametrizations. https://arxiv.org/abs/2511.15657

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