We measure the imprint of primordial baryon acoustic oscillations ( BAO ) in the correlation function of Ly \alpha 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- \alpha ( Ly \alpha ) region , we use , for the first time , Ly \alpha absorption in the Lyman- \beta region of 56,154 spectra .
We measure the Hubble distance , D _ { H } , and the comoving angular diameter distance , D _ { M } , relative to the sound horizon at the drag epoch r _ { d } at an effective redshift z = 2.34 .
Using a physical model of the correlation function outside the BAO peak , we find D _ { H } ( 2.34 ) / r _ { d } = 8.86 \pm 0.29 and D _ { M } ( 2.34 ) / r _ { d } = 37.41 \pm 1.86 , within 1 \sigma from the flat- \Lambda CDM 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-Ly \alpha cross-correlation measurement presented in a companion paper ( ) , the BAO measurements at z = 2.35 are within 1.7 \sigma of the predictions of this model .