The clustering of the SDSS-IV extended Baryon Oscillation Spectroscopic
  Survey DR14 quasar sample: First measurement of Baryon Acoustic Oscillations
  between redshift 0.8 and 2.2
  We present measurements of the Baryon Acoustic Oscillation (BAO) scale in
redshift-space using the clustering of quasars. We consider a sample of 147,000
quasars from the extended Baryon Oscillation Spectroscopic Survey (eBOSS)
distributed over 2044 square degrees with redshifts $0.8 < z < 2.2$ and measure
their spherically-averaged clustering in both configuration and Fourier space.
Our observational dataset and the 1400 simulated realizations of the dataset
allow us to detect a preference for BAO that is greater than 2.8$\sigma$. We
determine the spherically averaged BAO distance to $z = 1.52$ to 3.8 per cent
precision: $D_V(z=1.52)=3843\pm147 \left(r_{\rm d}/r_{\rm d, fid}\right)\ $Mpc.
This is the first time the location of the BAO feature has been measured
between redshifts 1 and 2. Our result is fully consistent with the prediction
obtained by extrapolating the Planck flat $\Lambda$CDM best-fit cosmology. All
of our results are consistent with basic large-scale structure (LSS) theory,
confirming quasars to be a reliable tracer of LSS, and provide a starting point
for numerous cosmological tests to be performed with eBOSS quasar samples. We
combine our result with previous, independent, BAO distance measurements to
construct an updated BAO distance-ladder. Using these BAO data alone and
marginalizing over the length of the standard ruler, we find $\Omega_{\Lambda}
> 0$ at 6.6$\sigma$ significance when testing a $\Lambda$CDM model with free
curvature.
