Parton distributions need representative sampling
Por:
Courtoy, Aurore, Huston, Joey, Nadolsky, Pavel, Xie, Keping, Yan, Mengshi, Yuan C.-P.
Publicada:
10 feb 2023
Resumen:
In global QCD fits of parton distribution functions (PDFs), a large part
of the estimated uncertainty on the PDFs originates from the choices of
parametric functional forms and fitting methodology. We argue that these
types of uncertainties can be underestimated with common PDF ensembles
in high-stake measurements at the Large Hadron Collider and Tevatron. A
fruitful approach to quantify these uncertainties is to view them as
arising from sampling of allowed PDF solutions in a multidimensional
parametric space. This approach applies powerful insights gained in
recent statistical studies of large-scale population surveys and
quasi-Monte Carlo integration methods. In particular, PDF fits may be
affected by the big data paradox, which stipulates that more
experimental data do not automatically raise the accuracy of PDFs-close
attention to the data quality and sampling of possible PDF solutions is
as essential. To test if the sampling of the PDF uncertainty of an
experimental observable is truly representative of all acceptable
solutions, we introduce a technique (''a hopscotch scan'') based on
a combination of parameter scans and stochastic sampling. With this
technique, we examine the PDF uncertainty on key LHC cross sections at
13 TeV obtained with the public NNPDF4.0 fitting code, while accounting
for the likelihood distribution. We show that the uncertainties on the
charm distribution at a large momentum fraction x and gluon PDF at small
x are enlarged. In PDF ensembles obtained in the analytic minimization
(Hessian) formalism, the tolerance on the PDF uncertainty must be based
on sufficiently complete sampling of PDF functional forms and choices of
the experiments.
Filiaciones:
Courtoy, Aurore:
Instituto de Física, Universidad Nacional Autónoma de México, Apartado Postal 20-364, Ciudad de México, 01000, Mexico
Univ Nacl Autonoma Mexico, Inst Fis, Apartado Postal 20-364, Mexico City 01000, Mexico
Huston, Joey:
Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, United States
Michigan State Univ, Dept Phys & Astron, E Lansing, MI 48824 USA
Nadolsky, Pavel:
Department of Physics, Southern Methodist University, Dallas, TX 75275-0181, United States
Southern Methodist Univ, Dept Phys, Dallas, TX 75275 USA
Xie, Keping:
Pittsburgh Particle Physics Astrophysics, and Cosmology Center, Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, United States
Univ Pittsburgh, Pittsburgh Particle Phys Astrophys & Cosmol Ctr, Dept Phys & Astron, Pittsburgh, PA 15260 USA
Yan, Mengshi:
School of Physics, State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing, 100871, China
Peking Univ, Sch Phys, Beijing 100871, Peoples R China
Peking Univ, State Key Lab Nucl Phys & Technol, Beijing 100871, Peoples R China
Yuan C.-P.:
Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, United States
hybrid, Green Submitted, Hybrid Gold
|