Reanalyzing DESI DR1: 4. Percent-Level Cosmological Constraints from Combined Probes and Robust Evidence for the Normal Neutrino Mass Hierarchy
We present cosmological parameter measurements from the full combination of DESI DR1 galaxy clustering data, described with large-scale structure effective field theory. By incorporating photometric galaxies and CMB lensing cross-correlations, and extending the bispectrum likelihood to smaller scales with a consistent one-loop computation, we achieve substantial gains in constraining power. Combined with the latest DESI baryon acoustic oscillation (BAO) data and cosmic microwave background (CMB) priors on the spectral tilt and baryon density, we find, in $\Lambda$CDM, $H_0=69.08\pm 0.37~\mathrm{km}\,\mathrm{s}^{-1}\mathrm{Mpc}^{-1}$, $\Omega_m=0.2974\pm 0.0050$, and $\sigma_8 = 0.838\pm 0.017$ ($S_8 = \sigma_8\sqrt{\Omega_m/0.3} =0.834\pm 0.018$). Adding the Pantheon+ supernovae (SNe), we find a $2.2\sigma$ preference for the $w_0w_a$ dynamical dark energy model from low-redshift data alone, rising to $2.7\sigma$ when exchanging the SNe for \textit{Planck} CMB data. Combining the full-shape, BAO, CMB, and SNe likelihoods improves the dark energy figure-of-merit by $15\%$ and bounds the neutrino mass sum to $M_\nu<0.049$ eV ($\Lambda$CDM) and $M_\nu<0.077$ eV ($w_0w_a$CDM) at 95\% CL. This is the strongest $w_0w_a$CDM bound to date, $37\%$ tighter than from the background expansion data alone. The preference for the normal neutrino mass ordering thus holds regardless of the background model: the inverted hierarchy is disfavored at ${\approx}\,3.5\sigma$ in $\Lambda$CDM and ${\approx}\,2.4\sigma$ in $w_0w_a$CDM, with the latter constraint free of the geometric tension between CMB and BAO that is known to sharpen the $\Lambda$CDM bound.