Statistical interpretation of sterile neutrino oscillation searches at reactors

Coloma, Pilar; Huber, Patrick; Schwetz, Thomas

doi:10.1140/epjc/s10052-020-08774-2

Statistical interpretation of sterile neutrino oscillation searches at reactors

Journal Article · Sat Jan 02 00:00:00 EST 2021 · European Physical Journal. C, Particles and Fields

DOI:https://doi.org/10.1140/epjc/s10052-020-08774-2· OSTI ID:1852596

Coloma, Pilar ^[1]; Huber, Patrick ^[2]; Schwetz, Thomas ^[3]

Univ. Autonoma de Madrid (Spain); Univ. of Valencia (Spain); Karlsruhe Inst. of Technology (KIT) (Germany)
Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)
Karlsruhe Inst. of Technology (KIT) (Germany)

A considerable experimental effort is currently under way to test the persistent hints for oscillations due to an eV-scale sterile neutrino in the data of various reactor neutrino experiments. The assessment of the statistical significance of these hints is usually based on Wilks’ theorem, whereby the assumption is made that the log-likelihood is χ²-distributed. However, it is well known that the preconditions for the validity of Wilks’ theorem are not fulfilled for neutrino oscillation experiments. In this work we derive a simple asymptotic form of the actual distribution of the log-likelihood based on reinterpreting the problem as fitting white Gaussian noise. From this formalism we show that, even in the absence of a sterile neutrino, the expectation value for the maximum likelihood estimate of the mixing angle remains non-zero with attendant large values of the log-likelihood. Our analytical results are then confirmed by numerical simulations of a toy reactor experiment. Finally, we apply this framework to the data of the Neutrino-4 experiment and show that the null hypothesis of no-oscillation is rejected at the 2.6 σ level, compared to 3.2 σ obtained under the assumption that Wilks’ theorem applies.

View Accepted Manuscript (DOE)

Research Organization:: Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)

Sponsoring Organization:: Spanish Agencia Estatal de Investigacion; Spanish MICINN; USDOE Office of Science (SC)

Grant/Contract Number:: SC0018327

OSTI ID:: 1852596

Alternate ID(s):: OSTI ID: 23036363

Journal Information:: European Physical Journal. C, Particles and Fields, Journal Name: European Physical Journal. C, Particles and Fields Journal Issue: 1 Vol. 81; ISSN 1434-6044

Publisher:: SpringerCopyright Statement

Country of Publication:: United States

Language:: English

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