Ball, Richard

Del Debbio, Luigi

Pearson, Rosalyn Laura

Science and Technology Facilities Council (STFC)

2022-02-15T10:17:18Z

2022-02-15T10:17:18Z

2021-11-17

We are now in the era of high precision particle physics, spurred on by a wealth of new data from the Large Hadron Collider (LHC). In order to match the precision set by modern experiments and test the limits of the Standard Model, we must increase the sophistication of our theoretical predictions. Much of the data available involve the interaction of protons, which are composite particles. These interactions are described by combining perturbative Quantum Chromodynamics (QCD) with parton distribution functions (PDFs), which encapsulate the non-perturbative behaviour. Increasing accuracy and precision of these PDFs is therefore of great value to modern particle physics. PDFs are determined by multi-dimensional fits of experimental data to theoretical predictions from QCD. Uncertainties in PDFs arise from those in the experimental data and theoretical predictions, as well as from the fitting procedure itself. Those in the theory come from many sources. Here we consider two of the most important: the first are missing higher order uncertainties (MHOUs), arising due to truncating the predictions’ perturbative expansion; the second are nuclear uncertainties, due to difficulty making predictions in a nuclear environment. In this thesis we consider how to include theory uncertainties in PDF fits by constructing a theory covariance matrix and adding this to the experimental one. MHOUs are estimated and included as a proof of concept in next-to-leading order PDFs. We find that these capture many of the important features of the known PDFs at the next order above. We then investigate nuclear uncertainties, estimate their magnitude and assess their impact on the PDFs. Finally, we consider how to make predictions with theory uncertainties using PDFs which themselves include theory uncertainties. Here there are correlations between the PDFs and the predictions, which can lead to a shift in the predictions and their uncertainties, which can significantly improve their accuracy and precision.

https://hdl.handle.net/1842/38570

http://dx.doi.org/10.7488/era/1834

en

The University of Edinburgh

Towards parton distribution functions with theoretical uncer tainties, Pearson, R. L. and Voisey, C. Nuclear and Particle Physics Proceedings, Volumes 300-302, July-September 2018, Pages 24-29, e-Print: 1810.01996

Nuclear Uncertainties in the Determination of Proton PDFs, NNPDF Collaboration: Richard D. Ball et al. (Dec 21, 2018), Published in: Eur.Phys.J.C 79 (2019) 3, 282, e-Print: 1812.09074

A first determination of parton distributions with theoretical uncertainties, NNPDF Collaboration: Rabah Abdul Khalek et al. (May 10, 2019), Published in: Eur.Phys.J. C (2019) 79:838, e-Print: 1905.04311

Uncertainties due to Nuclear Data in Proton PDF Fits, Rosalyn Pearson, Richard Ball, Emanuele Roberto Nocera (Jun 14, 2019), Published in: PoS DIS2019 (2019) 027, Contribution to: DIS 2019, 027

Parton Distributions with Theory Uncertainties: General For malism and First Phenomenological Studies, NNPDF Collaboration: Rabah Abdul Khalek et al. (Jun 25, 2019) Published in: Eur.Phys.J.C 79 (2019) 11, 931, e-Print: 1906.10698

Deuteron Uncertainties in the Determination of Proton PDFs, Richard D. Ball, Emanuele R. Nocera & Rosalyn L. Pearson (Oct 30, 2020) Published in: Eur.Phys.J.C 81 (2021) 1, 37, e-Print: 2011.00009

Correlation of Theoretical Uncertainties in PDF Fits and The oretical Uncertainties in Predictions, Richard D. Ball & Rosalyn L. Pearson (July 22, 2021), e-Print: 2105.05114v2

Next generation proton PDFs with deuteron and nuclear uncer tainties, Rosalyn L. Pearson, Richard D. Ball & Emanuele R. Nocera (Jun 23, 2021), e-Print: 2106.12349

parton distribution functions

particle physics

nnpdf

proton

Theory uncertainties in parton distribution functions

Thesis or Dissertation

Doctoral

PhD Doctor of Philosophy