Standard Model (SM) describes elementary particles and interactions among them. Its predictions agree extremely well with colliders’ data. In order to search for any deviation from the SM in measurements at colliders, which could be a hint of new physics beyond the SM, one needs to achieve high precision in SM predictions.
The basic tool to obtain predictions for physical observables at high-energy hadron colliders is the collinear factorization theorem in Quantum Chromodynamics (QCD), which assumes that partons inside a proton are moving collinearly with it. However, it turns out that for certain observables also the parton’s transverse momentum needs to be taken into account in order to obtain sufficient precision. In this talk I present the Parton Branching (PB) method to describe transverse momentum dependent (TMD) parton distribution functions (PDFs), which are the basis for precise predictions.
I explain the basic elements of the PB method and illustrate its relationship with the QCD renomalization group evolution given by DGLAP (Dokshitzer-Gribov-Lipatov-Altarelli-Parisi) equations. I show the application of the method to predictions for deep inelastic scattering measurements of proton's structure functions and for Drell-Yan Z-boson production at the Large Hadron Collider. The method allows one to investigate detailed features of the QCD radiation associated with colliders’ hard-scattering processes. I present ongoing studies of the angular ordering of multiple soft-gluon radiation, and compare the PB method with other approaches existing in the literature.
Ioana Maris