{
  "annotation_id": "ddb07f2f-ec04-4bc5-9c75-c37395a6617c",
  "date_created": "2026-02-17T05:53:20.287000Z",
  "date_modified": "2026-02-17T05:53:20.287000Z",
  "file_hash": "59fc412b2423985469687f636da1226b82dda1dfc2e0aca99551452abd23d61d",
  "private": false,
  "record": {
    "abstract": "Recent studies report a mild discrepancy between baryon acoustic oscillation (BAO) and cosmic microwave background (CMB) measurements within the $\\Lambda$CDM framework. This discrepancy could be explained if the optical depth $\\tau$ inferred from the CMB large-scale E-mode polarization is underestimated, which may be biased by foreground-subtraction or instrumental systematics. In this work, we present a determination of $\\tau$ independent of the large-scale E-mode polarization, using the latest measurements of the redshift evolution of the neutral hydrogen fraction $x_\\mathrm{HI}(z)$, which is constrained by Lyman-$\\alpha$ forest and damping-wing absorption measurements at $z\\sim5$-$14$, based on ground-based optical and JWST observations. Combining $x_\\mathrm{HI}(z)$ with the Planck CMB power spectra excluding the large-scale E-mode polarization, we obtain $\\tau=0.0552^{+0.0019}_{-0.0026}$, a stringent constraint consistent with the previous CMB results including the large-scale E-mode. We also evaluate a potential systematic error in our method associated with absorption modeling, obtaining $\\tau=0.0552^{+0.0075}_{-0.0049}$. Using this constraint on $\\tau$, we resolve the degeneracy in the $\\tau$-$\\Omega_m$ plane and find a $2.4\\sigma$ tension with the DESI DR2 BAO results, thereby confirming the claimed mild discrepancy suggestive of physics beyond $\\Lambda$CDM. Finally, we derive an upper limit on the sum of neutrino masses, $\\Sigma m_\\nu\u003c0.0550\\,(0.0717)$ eV at the 95% (99%) confidence level. This limit favors the normal mass ordering and, when combined with the lower limits from neutrino oscillation experiments, yields a further constraint, $\\Sigma m_\\nu=0.0594_{-0.0007}^{+0.0113}$ eV. However, the cosmological upper limit and the oscillation-based lower limit show a mild $2.2\\sigma$ tension, providing an independent indication of possible physics beyond $\\Lambda$CDM.",
    "arxiv_id": "2601.09644",
    "authors": [
      "Yuta Kageura",
      "Masami Ouchi",
      "Fumihiro Naokawa",
      "Hiroya Umeda",
      "Akinori Matsumoto",
      "Yuichi Harikane",
      "Minami Nakane",
      "Tran Thi Thai"
    ],
    "categories": [
      "astro-ph.CO",
      "astro-ph.GA"
    ],
    "license": "http://creativecommons.org/licenses/by/4.0/",
    "title": "A New Constraint on the Optical Depth from the Reionization History Independent of CMB Large-Scale E-Mode Polarization",
    "url": "https://arxiv.org/abs/2601.09644",
    "version": "v1"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "595295c9-5995-4be1-9061-f53190c966ab",
    "id": "arXiv Dataset",
    "type": "Model",
    "variant": "snapshot-2026-01-17",
    "version": "0.1.0"
  },
  "user_id": 1000002
}