https://doi.org/10.1140/epjc/s10052-022-10932-7
Regular Article - Theoretical Physics
Regularising experimental correlations in LHC data: theory and application to a global analysis of parton distributions
1
DAMTP, University of Cambridge, Wilberforce Road, CB3 0WA, Cambridge, UK
2
The Higgs Centre for Theoretical Physics, University of Edinburgh JCMB, Mayfield Rd, EH9 3JZ, Edinburgh, KB, UK
b
emanuele.roberto.nocera@gmail.com
Received:
8
July
2022
Accepted:
17
October
2022
Published online:
27
October
2022
We show how an inaccurate determination of experimental uncertainty correlations in high-precision LHC measurements may undermine the reliability of the associated 
. We formulate the problem rigorously, and devise a regularisation procedure that increases the stability of the by altering the covariance matrix of the measurement as little as possible. We apply the procedure to the NNPDF4.0 global analysis of parton distribution functions that utilises a large amount of LHC measurements. We find that the regularised of the NNPDF4.0 determination is lowered by about 
, without significantly altering the resulting PDFs upon refitting.
© The Author(s) 2022
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