Left panel: distribution of the redshift of quasars (blue) and forest pixels (green) with the redshift for the latter calculated assuming Lyα absorption. The pixels are weighted as described in Sect. 4.1. Right panel: weighted distribution of the redshift of the 1.8 × 10⁹ pixel-quasar pairs in the BAO region: r_pair ∈ [80,120] h^-1 Mpc. The redshift of a pair is defined by: z_pair = (z_pixel + z_QSO)/2. The weighted mean redshift of the pairs (dashed black line) defines the mean redshift, z_eff = 2.40, of the measurement of the BAO peak position.