Abstract
We study parton-branching solutions of QCD evolution equations and present a method to construct both collinear and transverse momentum dependent (TMD) parton densities from this approach. We work with next-to-leading-order (NLO) accuracy in the strong coupling. Using the unitarity picture in terms of resolvable and non-resolvable branchings, we analyze the role of the soft-gluon resolution scale in the evolution equations. For longitudinal momentum distributions, we find agreement of our numerical calculations with existing evolution programs at the level of better than 1% over a range of five orders of magnitude both in evolution scale and in longitudinal momentum fraction. We make predictions for the evolution of transverse momentum distributions. We perform fits to the high-precision deep inelastic scattering (DIS) structure function measurements, and we present a set of NLO TMD distributions based on the parton branching approach.
Highlights
Deep inelastic scattering (DIS) data [34, 35], and used in a parton shower calculation [18] to make predictions for W -boson + jets hadro-production, which can be compared with LHC experimental measurements [36, 37]
We study parton-branching solutions of QCD evolution equations and present a method to construct both collinear and transverse momentum dependent (TMD) parton densities from this approach
We have shown that a consistent set of TMD parton distributions, valid over a large range in x, k⊥ and μ can be determined from a parton branching solution of QCD evolution equations, as long as the soft gluon region is treated appropriately, e.g. by applying angular ordering conditions
Summary
We give the main elements of the parton-branching approach to the evolution equations. We introduce a soft-gluon resolution scale into the renormalization group evolution equations, and describe resolvable and non-resolvable emissions. We discuss the relationship of our results with the angular-ordered, coherent branching [70,71,72,73] and the behavior of the endpoint z → 1 region in transverse momentum distributions [74, 75]. We construct an iterative Monte Carlo solution of the evolution equations, and apply it to the case of collinear and TMD parton densities
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
