Latest Results from DESI: Neutrino Masses in Focus

Latest Results from DESI: Neutrino Masses in Focus 1 Q Continuum Graziano Rossi Department of Physics & Astronomy Sejong University Seoul, Korea XXI International Workshop on Neutrino Telescopes Padova, IT September 30, 2025 @DESI 2025 DESI DR1 (Year 1) Released! 2 @Graziano Rossi 2025 DESI DR2 (Year 3) New Results 3 @Graziano Rossi 2025 Outline & Primary References 4 @Graziano Rossi 2025 1. DESI Experiment 2. DESI Latest Results: Dark Energy 3. DESI Latest Results: Neutrinos • Synergies, Contributions, Outlook •DESI DR2 Results II – 2025, arXiv:2503.14738 (DR2 Key Paper) •DESI 2024 VII – JCAP Vol. 2025, Issue 07, id. 028 (DR1 Key Paper) •DESI 2024 VI – JCAP Vol. 2025, Issue 02, id. 021 (DR1 Key Paper) 1. DESI Experiment 5 @Graziano Rossi 2025 DESI: A Stage-IV Experiment 6 @Graziano Rossi 2025 DESI Instrument 7 @Graziano Rossi 2025 DESI Science 8 @Graziano Rossi 2025 DESI à order-of-mag improvement in volume surveyed & in # of galaxies over SDSS-IV eBOSS DESI Collaboration @Hawaii, December 2023 DESI Collab. (2016) DESI Largest 3D Map of the Universe 9 @Graziano Rossi 2025 @DESI 2025 LCDM still Holds … but … Tensions ? 16 @Graziano Rossi 2025 PLANCK 2018 (Planck Coll. 2020 -VI) POPULAR THESE DAYS IN COSMOLOGY à`Hubble Tension’ w = P/! w(z) = w0+ waz /(1+z) ΛCDM àSpatially-flat minimal 6-parameter model, DE as Λ with c2!DE constant àw=-1 w0waCDM àExtension of ΛCDM with z-evolution of DE EoS DE EoS: CPL parameterization DESI DR2 Results II: arXiv:2503.14738 DESI DR1/DR2: Dark Energy 17 @Graziano Rossi 2025 •DESI DR2 BAO results àconsistent with DESI DR1 and SDSS •DESI DR2 BAO àwell described by flat ΛCDM model! •DESI flat ΛCDM parameters in 2.3σ tension with CMB •DESI flat ΛCDM parameters up to 2.9σ tension with SNe •Results point to incompatibility between datasets within ΛCDM •DESI DR2 BAO àno strong preference for evolving DE (1.7σ) •DESI DR2 + CMB àΛCDM model disfavored at 3.1σto w0waCDM •DESI DR2 + CMB + SNe àΛCDM model disfavored up to 4.2σto w0waCDM DESI DR2 Results II: arXiv:2503.14738 •DESI DR1 + CMB àΛCDM model disfavored at 2.6σto w0waCDM •DESI DR1 + CMB + DESY5 àΛCDM model disfavored at 3.9σto w0waCDM DESI DR1 DESI DR2 • ΛCDM challenged by DESI BAO + additional probes • Dynamical DE possible solution ? New! DESI DR2: Dark Energy 18 @Graziano Rossi 2025 Flat ! CDM DESI DR2 Results II: arXiv:2503.14738 Flat w0-waCDM 3. DESI Latest Results: Neutrinos 19 @Graziano Rossi 2025 DESI DR1: Neutrino Mass Constraints 20 @Graziano Rossi 2025 With Mν> 0 eV prior & 3 degenerate neutrino mass states •DESI DR1 (FS+BAO) + BBN + ns,10 àMν< 0.409 eV (95%) •DESI DR1 (FS+BAO) + CMB (plik) àMν< 0.072 eV (95%) With Mν> 0 eV prior & 3 degenerate neutrino mass states •DESI DR1 (FS+BAO) + CMB + DESY5 àMν< 0.196 eV (95%) (consistent with neutrino oscillations for NH or IH) Flat ! CDM + Mν Flat w0-waCDM + Mν Puzzling aspects of DESI analysis (both BAO and FS) • Strongest constraints in tension (~2σ) with neutrino oscillations • Marginalized posterior distribution of Mνpeaks at lower edge of prior Mν> 0 eV àtail of distribution with central value in negative mass range & posterior away from its maximum likelihood value DESI 2024 VI: JCAP Vol. 2025, Issue 02 DESI DR1: Neutrinos 21 @Graziano Rossi 2025 DESI 2024 VI: JCAP Vol. 2025, Issue 02 • Mν< 0.072 (0.113) eV at 95% confidence for a Mν> 0 (Mν> 0.059) eV prior Flat ! CDM DESI DR2: Neutrino Mass Constraints 22 @Graziano Rossi 2025 DESI DR2 BAO + CMB (baseline) àMν< 0.0642 eV (95%) Flat ! CDM + Mν Flat w0-waCDM + Mν Flat wCDM + Mν With Mν> 0 eV prior & 3 degenerate neutrino mass states DESI DR2 BAO + CMB (baseline) àMν< 0.0851 eV (95%) DESI DR2 BAO + CMB (baseline) àMν< 0.163 eV (95%) 20% reduction from DR1 Significant relaxation of neutrino constraints DESI DR2: Neutrino Mass Constraints 23 @Graziano Rossi 2025 DESI DR2 Results II: arXiv:2503.14738 `Prior weight effect’ àIn a model with effective Mνpeak of DESI+CMB likelihood <0 with 3σ tension with terrestrial bounds Mνand Ωmpositively correlated à DESI preference for lower Ωmthan CMB drives small Mνconstraints! Flat ! CDM DESI DR2: Neutrino Mass Constraints 24 @Graziano Rossi 2025 DESI DR2 Results II: arXiv:2503.14738 DESI DR2: Neutrino Mass Constraints 25 @Graziano Rossi 2025 Flat w0waCDM + Mν DESI DR2 Results II: arXiv:2503.14738 Key Results & Main Messages: Neutrinos 32 @Graziano Rossi 2025 DESI DR2 Results II: arXiv:2503.14738 Flat ! CDM Flat w0-waCDM •Give up ΛCDM? Negative neutrino mass? •Moderate tension with lower limits from neutrino oscillations (Ωm-driven) •Beyond traditional methods Moon, Rossi, Yu (2023), ApJS ? 33 @Graziano Rossi 2025