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We present a measurement of the baryon acoustic oscillation (BAO) scale at redshift z = 2.35 from the three-dimensional correlation of Lyman-α (Lyα) forest absorption and quasars. The study uses 266 590 quasars in the redshift range 1.77 <  z <  3.5 from the Sloan Digital Sky Survey (SDSS) Data Release 14 (DR14). The sample includes the first two years of observations by the SDSS-IV extended Baryon Oscillation Spectroscopic Survey (eBOSS), providing new quasars and re-observations of BOSS quasars for improved statistical precision. Statistics are further improved by including Lyα absorption occurring in the Lyβ wavelength band of the spectra. From the measured BAO peak position along and across the line of sight, we determined the Hubble distance DH and the comoving angular diameter distance DM relative to the sound horizon at the drag epoch rd: DH(z = 2.35)/rd = 9.20 ± 0.36 and DM(z = 2.35)/rd = 36.3 ± 1.8. These results are consistent at 1.5σ with the prediction of the best-fit spatially-flat cosmological model with the cosmological constant reported for the Planck (2016) analysis of cosmic microwave background anisotropies. Combined with the Lyα auto-correlation measurement presented in a companion paper, the BAO measurements at z = 2.34 are within 1.7σ of the predictions of this model. [ABSTRACT FROM AUTHOR]

We measure the imprint of primordial baryon acoustic oscillations (BAOs) in the correlation function of Lyα absorption in quasar spectra from the Baryon Oscillation Spectroscopic Survey (BOSS) and the extended BOSS (eBOSS) in Data Release 14 (DR14) of the Sloan Digital Sky Survey (SDSS)-IV. In addition to 179 965 spectra with absorption in the Lyman-α (Lyα) region, we use Lyα absorption in the Lyman-β region of 56 154 spectra for the first time. We measure the Hubble distance, DH, and the comoving angular diameter distance, DM, relative to the sound horizon at the drag epoch rd at an effective redshift z = 2.34. Using a physical model of the correlation function outside the BAO peak, we find DH(2.34)/rd = 8.86 ± 0.29 and DM(2.34)/rd = 37.41 ± 1.86, within 1σ from the flat-ΛCDM model consistent with CMB anisotropy measurements. With the addition of polynomial "broadband" terms, the results remain within one standard deviation of the CMB-inspired model. Combined with the quasar-Lyα cross-correlation measurement presented in a companion paper, the BAO measurements at z = 2.35 are within 1.7σ of the predictions of this model. [ABSTRACT FROM AUTHOR]