Precision boson-jet azimuthal decorrelation at hadron colliders

Abstract

The azimuthal angular decorrelation of a vector boson and jet is sensitive to QCD radiation, and can be used to probe the quark-gluon plasma in heavy-ion collisions. By using a recoil-free jet definition, the sensitivity to contamination from soft radiation on the measurement is reduced, and the complication of non-global logarithms is eliminated from our theoretical calculation. Specifically we will consider the $p_T^n$ recombination scheme, as well as the n → ∞ limit, known as the winner-take-all scheme. These jet definitions also significantly simplify the calculation for a track-based measurement, which is preferred due to its superior angular resolution. We present a detailed discussion of the factorization in Soft-Collinear Effective Theory, revealing why the transverse momentum ${\overrightarrow{q}}_T$ is more complicated than the azimuthal angle. We show that potential glauber contributions do not spoil our factorization formalism, at least up to and including order ${\alpha }_s^3$. The resummation is carried out using the renormalization group, and all necessary ingredients are collected or calculated. We conclude with a detailed phenomenological study, finding an enhanced matching correction for high jet p_T due to the electroweak collinear enhancement of a boson emission off di-jets. We also compare with the Pythia event generator, finding that our observable is very robust to hadronization and the underlying event.