A new quantity for studies of dijet azimuthal decorrelations
We introduce a new measurable quantity, $R_{Δϕ}$, for studies of the rapidity and transverse momentum dependence of dijet azimuthal decorrelations in hadron-hadron collisions. In pQCD, $R_{Δϕ}$ is computed as a ratio of three-jet and dijet cross sections in which the parton distribution functions cancel to a large extent. At the leading order, $R_{Δϕ}$ is proportional to $α_s$, and the transverse momentum dependence of can therefore be exploited to determine $α_s$. We compute the NLO pQCD theory predictions and non-perturbative corrections for $R_{Δϕ}$ at the LHC and the Tevatron and investigate the corresponding uncertainties. From this, we estimate the theory uncertainties for $α_s$ determinations based on $R_{Δϕ}$ at both colliders. The potential of $R_{Δϕ}$ measurements for tuning Monte Carlo event generators is also demonstrated.