Measurement of differential cross sections in the kinematic angular variable ${\varphi }^{\ast }$ for inclusive Z boson production in pp collisions at $\sqrt{s}=$ 8 TeV

Measurements of differential cross sections d$\sigma$/d${\varphi }^{\ast }$ and double-differential cross sections d${}^2\sigma$/d${\varphi }^{\ast }$d$\mathrm{\mid }y\mathrm{\mid }$ for inclusive Z boson production are presented using the dielectron and dimuon final states. The kinematic observable ${\varphi }^{\ast }$ correlates with the dilepton transverse momentum but has better resolution, and $y$ is the dilepton rapidity. The analysis is based on data collected with the CMS experiment at a centre-of-mass energy of 8 TeV corresponding to an integrated luminosity of 19.7 fb${}^{-1}$. The normalised cross section (1/$\sigma$)$$d$\sigma$/d${\varphi }^{\ast }$, within the fiducial kinematic region, is measured with a precision of better than 0.5% for ${\varphi }^{\ast }$ < 1. The measurements are compared to theoretical predictions and they agree, typically, within few percent.