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Abstract
It has been argued from the earliest days of quantum chromodynamics (QCD) that at asymptotically small values of $x$ the parton distribution functions (PDFs) of the proton behave as $x^\alpha$, where the values of $\alpha$ can be deduced from Regge theory, while at asymptotically large values of $x$ the PDFs behave as $(1x)^\beta$, where the values of $\beta$ can be deduced from the BrodskyFarrar quark counting rules. We critically examine these claims by extracting the exponents $\alpha$ and $\beta$ from various global fits of parton distributions, analysing their scale dependence, and comparing their values to the naive expectations. We find that for valence distributions both Regge theory and counting rules are confirmed, at least within uncertainties, while for sea quarks and gluons the results are less conclusive. We also compare results from various PDF fits for the structure function ratio $F_2^n/F_2^p$ at large $x$, and caution against unrealistic uncertainty estimates due to overconstrained parametrisations.
Original language  English 

Journal  The European Physical Journal C (EPJ C) 
DOIs  
Publication status  Published  8 Jul 2016 
Keywords
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Dive into the research topics of 'The asymptotic behaviour of parton distributions at small and large $x$'. Together they form a unique fingerprint.Projects
 1 Finished

Particle Theory at the Higgs Centre
Ball, R., Berera, A., Boyle, P., CallisonBurch, C., Del Debbio, L., Gardi, E., Kennedy, A., O'Connell, D., Zwicky, R., Berera, A., Boyle, P., Buckley, A., Del Debbio, L., Gardi, E., Horsley, R., Kennedy, A., Kenway, R., O'Connell, D., Smillie, J. & Zwicky, R.
1/10/14 → 30/09/18
Project: Research