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Abstract
We study longdistance singularities governing different physical quantities involving massless partons in perturbative QCD by using factorisation in terms of Wilsonline correlators. By isolating the processindependent hardcollinear singularities from quark and gluon form factors, and identifying these with the ones governing the elastic limit of the perturbative Parton Distribution Functions (PDFs)  $\delta(1x)$ in the large$x$ limit of DGLAP splitting functions  we extract the anomalous dimension controlling soft singularities of the PDFs, verifying that it admits Casimir scaling. We then perform an independent diagrammatic computation of the latter using its definition in terms of Wilson lines, confirming explicitly the above result through two loops. By comparing our eikonal PDF calculation to that of the eikonal form factor by Erdogan and Sterman and the classical computation of the closed parallelogram by Korchemsky and Korchemskaya, a consistent picture emerges whereby all singularities emerge in diagrammatic configurations localised at the cusps or along lightlike lines, but where distinct contributions to the anomalous dimensions are associated with finite (closed) lightlike segments as compared to infinite (open) ones. Both are relevant for resumming large logarithms in physical quantities, notably the anomalous dimension controlling DrellYan or Higgs production near threshold on the one hand, and the gluon Regge trajectory controlling the highenergy limit of partonic scattering on the other.
Original language  English 

Number of pages  53 
Journal  Journal of High Energy Physics 
DOIs  
Publication status  Published  18 Nov 2019 
Keywords
 hepph
 hepth
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Projects
 1 Active

Particle Theory at the Higgs Centre
Ball, R., Boyle, P., Del Debbio, L., Gardi, E., Horsley, R., Kennedy, A., O'Connell, D., Smillie, J. & Zwicky, R.
1/10/17 → 30/09/21
Project: Research