The clustering of the SDSS-IV extended Baryon Oscillation Spectroscopic
  Survey DR14 quasar sample: measuring the evolution of the growth rate using
  redshift space distortions between redshift 0.8 and 2.2
  We measure the growth rate and its evolution using the anisotropic clustering
of the extended Baryon Oscillation Spectroscopic Survey (eBOSS) Data Release 14
(DR14) quasar sample, which includes $148\,659$ quasars covering the wide
redshift range of $0.8 < z < 2.2$ and a sky area of $2112.90$ $\rm deg^2$. To
optimise measurements we deploy a redshift-dependent weighting scheme, which
allows us to avoid binning, and perform the data analysis consistently
including the redshift evolution across the sample. We perform the analysis in
Fourier space, and use the redshift evolving power spectrum multipoles to
measure the redshift space distortion parameter $f\sigma_8$ and parameters
controlling the anisotropic projection of the cosmological perturbations. We
measure $f \sigma_8(z=1.52)=0.43 \pm 0.05 $ and $df\sigma_8/dz (z=1.52)= - 0.16
\pm 0.08$, consistent with the expectation for a $\Lambda$CDM cosmology as
constrained by the Planck experiment.
