CMB lensing and Lyα forest cross bispectrum from DESI's first-year quasar sample

The squeezed cross-bispectrum Bκ,Lyα between the gravitational lensing in the cosmic microwave background and the 1D Lyα forest power spectrum can constrain bias parameters and break degeneracies between σ8 and other cosmological parameters. We detect Bκ,Lyα with 4.8σ significance at an effective redshift zeff=2.4 using Planck PR3 lensing map and over 280,000 quasar spectra from the Dark Energy Spectroscopic Instrument's first-year data. We test our measurement against metal contamination and foregrounds such as Galactic extinction and clusters of galaxies by deprojecting the thermal Sunyaev-Zeldovich effect. We compare our results to a tree-level perturbation theory calculation and find reasonable agreement between the model and measurement.