Statistical methods applied to the search of sterile neutrinos

Agostini, M.; Neumair, B.

doi:10.1140/epjc/s10052-020-8279-x

Cited by 33 publications

(40 citation statements)

References 39 publications

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“…4 we will compute the distribution of T for more realistic configurations and will always confirm rather large deviations from a χ 2distribution. This suggests that reliable statements about significance and confidence levels require explicit Monte-Carlo simulations, in agreement with previous results [27,28]. We will demonstrate this explicitly using the recent results from Neutrino-4 in Sect.…”

Section: General Remarkssupporting

confidence: 86%

“…1 leads to a strong non-linear behavior. Therefore, significant deviations of the distribution of T from a χ 2 -distribution are expected a priori, see also [27,31]. A recent review discussing the applicability of Wilk's theorem can be found in Ref.…”

Section: General Remarksmentioning

confidence: 99%

“…This has recently been pointed out in Refs. [27][28][29], where the authors have shown by way of Monte Carlo simulations that there are indeed corrections and that the statistical significance of the hints is reduced. In this paper we attempt to go one step further and, besides providing analytical arguments that allow to understand the expected distribution for the test statistics, we also study the dependence of the observed corrections on relevant experimental parameters and numerical details of the analysis.…”

Section: Introductionmentioning

confidence: 99%

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Statistical interpretation of sterile neutrino oscillation searches at reactors

Coloma

Schwetz

2021

Eur. Phys. J. C

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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 $$\chi ^2$$ χ 2 -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 $$\sigma $$ σ level, compared to 3.2 $$\sigma $$ σ obtained under the assumption that Wilks’ theorem applies.

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Section: General Remarkssupporting

confidence: 86%

Section: General Remarksmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Statistical interpretation of sterile neutrino oscillation searches at reactors

Coloma

Schwetz

2021

Eur. Phys. J. C

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“…Before discussing our results, let us point out that the determination of the sensitivity to sterile neutrinos from oscillations is non-trivial from the statistical point of view. In particular, the results obtained under the assumption that Wilks' theorem [95] applies may differ from the ones obtained via Monte Carlo simulation [43,[96][97][98]. The sensitivity contours in this work have however been computed under the assumption that Wilks' theorem applies, in order to ease the comparison with previous literature.…”

Section: Sterile Neutrinosmentioning

confidence: 98%

New physics from oscillations at the DUNE near detector, and the role of systematic uncertainties

Coloma

López‐Pavón

Rosauro-Alcaraz

et al. 2021

J. High Energ. Phys.

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We study the capabilities of the DUNE near detector to probe deviations from unitarity of the leptonic mixing matrix, the 3+1 sterile formalism and Non-Standard Interactions affecting neutrino production and detection. We clarify the relation and possible mappings among the three formalisms at short-baseline experiments, and we add to current analyses in the literature the study of the νμ→ ντ appearance channel. We study in detail the impact of spectral uncertainties on the sensitivity to new physics using the DUNE near detector, which has been widely overlooked in the literature. Our analysis shows that this plays an important role on the results and, in particular, that it can lead to a strong reduction in the sensitivity to sterile neutrinos from νμ→ νe transitions, by more than two orders of magnitude. This stresses the importance of a joint experimental and theoretical effort to improve our understanding of neutrino nucleus cross sections, as well as hadron production uncertainties and beam focusing effects. Nevertheless, even with our conservative and more realistic implementation of systematic uncertainties, we find that an improvement over current bounds in the new physics frameworks considered is generally expected if spectral uncertainties are below the 5% level.

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“…A common source of error in statistical analysis is to assume that the test statistic follows a χ 2 distribution with mean equal to the degrees of freedom (dof's) according to Wilks' theorem [105]. This is often not correct and can lead to significantly incorrect results [75,106,107], as it has been pointed out recently in the context of short baseline neutrino oscillations [108][109][110][111][112][113][114] and for the determinations of the leptonic CP phase [115][116][117][118]. In fact for low number of events per bin the test statistic is not expected to follow a χ 2 distribution as in this case the necessary condition to fulfill Wilks' theorem that enough data is observed is not met (see for example [107]).…”

mentioning

confidence: 99%

A statistical analysis of the COHERENT data and applications to new physics

Denton

Gehrlein

2021

J. High Energ. Phys.

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The observation of coherent elastic neutrino nucleus scattering (CEνNS) by the COHERENT collaboration in 2017 has opened a new window to both test Standard Model predictions at relatively low energies and probe new physics scenarios. Our investigations show, however, that a careful treatment of the statistical methods used to analyze the data is essential to derive correct constraints and bounds on new physics parameters. In this manuscript we perform a detailed analysis of the publicly available COHERENT CsI data making use of all available background data. We point out that Wilks’ theorem is not fulfilled in general and a calculation of the confidence regions via Monte Carlo simulations following a Feldman-Cousins procedure is necessary. As an example for the necessity of this approach to test new physics scenarios we quantify the allowed ranges for several scenarios with neutrino non-standard interactions. Furthermore, we provide accompanying code to enable an easy implementation of other new physics scenarios as well as data files of our results: https://github.com/JuliaGehrlein/7stats.

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Statistical methods applied to the search of sterile neutrinos

Cited by 33 publications

References 39 publications

Statistical interpretation of sterile neutrino oscillation searches at reactors

Statistical interpretation of sterile neutrino oscillation searches at reactors

New physics from oscillations at the DUNE near detector, and the role of systematic uncertainties

A statistical analysis of the COHERENT data and applications to new physics

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