3D Correlations in the Lyman-\(\alpha\) Forest from Early DESI Data

We present the first measurements of Lyman-\(\alpha\) (Ly\(\alpha\)) forest correlations using early data from the Dark Energy Spectroscopic Instrument (DESI). We measure the auto-correlation of Ly\(\alpha\) absorption using 88,509 quasars at \(z>2\), and its cross-correlation with quasars using a further 147,899 tracer quasars at \(z\gtrsim1.77\). Then, we fit these correlations using a 13-parameter model based on linear perturbation theory and find that it provides a good description of the data across a broad range of scales. We detect the BAO peak with a signal-to-noise ratio of \(3.8\sigma\), and show that our measurements of the auto- and cross-correlations are fully-consistent with previous measurements by the Extended Baryon Oscillation Spectroscopic Survey (eBOSS). Even though we only use here a small fraction of the final DESI dataset, our uncertainties are only a factor of 1.7 larger than those from the final eBOSS measurement. We validate the existing analysis methods of Ly\(\alpha\) correlations in preparation for making a robust measurement of the BAO scale with the first year of DESI data.