Measurements of the $\phi_{\eta}^*$ distribution of $Z\rightarrow \mu^+\mu^-$ events in $p\bar{p}$ collisions at ${\sqrt{s}=}$ 1.96 TeV and measurements of the isolated diphoton cross section in $pp$ collisions at ${\sqrt{s}=}\ $ 8 TeV

Two precision measurements have been performed using the large number of dilepton and diphoton events produced in $p\bar{p}$ and $pp$ collisions. A measurement of the distribution of the kinematic variable $\phi_{\eta}^*$ in the Drell-Yan process is performed in bins of boson rapidity and invariant mass using 10.4 fb$^{-1}$ data collected by the D0 experiment with a centre-of-mass energy of 1.96~TeV in $p\bar{p}$ collisions. $\phi_{\eta}^*$, defined in terms of lepton track directions, is well-measured and is sensitive to higher order effects in Quantum chromodynamics (QCD). Data are compared to predictions from state-of-the-art QCD Monte Carlo programs and are in good agreement. Measurements of the production of prompt photon pairs are performed using 20.24 fb$^{-1}$ data collected by the ATLAS experiment at 8~TeV in $pp$ collisions. QCD Monte Carlo programs including higher order effects are found to describe the data. In addition, a luminosity algorithm that renders its susceptibility to noise and inefficiency of certain modules in the diamond beam monitor has been proposed and validated using ATLAS simulations.