Aarhus Universitets segl

Neutrino mass and mass ordering: no conclusive evidence for normal ordering

Publikation: Bidrag til tidsskrift/Konferencebidrag i tidsskrift /Bidrag til avisTidsskriftartikelForskningpeer review

  • Stefano Gariazzo, National Institute for Nuclear Physics
  • ,
  • Martina Gerbino, National Institute for Nuclear Physics
  • ,
  • Thejs Brinckmann, National Institute for Nuclear Physics, University of Ferrara
  • ,
  • Massimiliano Lattanzi, National Institute for Nuclear Physics
  • ,
  • Olga Mena, Polytechnic University of Valencia
  • ,
  • Thomas Schwetz, Karlsruhe Institute of Technology
  • ,
  • Shouvik Roy Choudhury, Indian Institute of Technology, Bombay, Inter-University Centre for Astronomy and Astrophysics India
  • ,
  • Katherine Freese, University of Texas at Austin, Oskar Klein Centre
  • ,
  • Steen Hannestad
  • Christoph A. Ternes, National Institute for Nuclear Physics
  • ,
  • Mariam Tórtola, Polytechnic University of Valencia

The extraction of the neutrino mass ordering is one of the major challenges in particle physics and cosmology, not only for its implications for a fundamental theory of mass generation in nature, but also for its decisive role in the scale of future neutrinoless double beta decay experimental searches. It has been recently claimed that current oscillation, beta decay and cosmological limits on the different observables describing the neutrino mass parameter space provide robust decisive Bayesian evidence in favor of the normal ordering of the neutrino mass spectrum [1]. We further investigate these strong claims using a rich and wide phenomenology, with different sampling techniques of the neutrino parameter space. Contrary to the findings of Jimenez et al. [1], no decisive evidence for the normal mass ordering is found. Neutrino mass ordering analyses must rely on priors and parameterizations that are ordering-agnostic: robust results should be regarded as those in which the preference for the normal neutrino mass ordering is driven exclusively by the data, while we find a difference of up to a factor of 33 in the Bayes factors among the different priors and parameterizations exploited here. An ordering-agnostic prior would be represented by the case of parameterizations sampling over the two mass splittings and a mass scale, or those sampling over the individual neutrino masses via normal prior distributions only. In this regard, we show that the current significance in favor of the normal mass ordering should be taken as 2.7σ (i.e. moderate evidence), mostly driven by neutrino oscillation data. Let us stress that, while current data favor NO only mildly, we do not exclude the possibility that this may change in the future. Eventually, upcoming oscillation and cosmological data may (or may not) lead to a more significant exclusion of IO.

TidsskriftJournal of Cosmology and Astroparticle Physics
StatusUdgivet - okt. 2022

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