Improved sterile neutrino constraints from the STEREO experiment with 179 days of reactor-on data

The STEREO collaboration
Phys.Rev.D 102 (2020) 052002, 2020.

Abstract (data abstract)
The STEREO experiment is a very short baseline reactor antineutrino experiment. It is designed to test the hypothesis of light sterile neutrinos being the cause of a deficit of the observed antineutrino interaction rate at short baselines with respect to the predicted rate, known as the Reactor Antineutrino Anomaly. The STEREO experiment measures the antineutrino energy spectrum in six identical detector cells covering baselines between 9 and 11 m from the compact core of the ILL research reactor. In this article, results from 179 days of reactor turned on and 235 days of reactor turned off are reported at a high degree of detail. The current results include improvements in the modelling of detector optical properties and the gamma-cascade after neutron captures by gadolinium, the treatment of backgrounds, and the statistical method of the oscillation analysis. Using a direct comparison between antineutrino spectra of all cells, largely independent of any flux prediction, we find the data compatible with the null oscillation hypothesis. The best-fit point of the Reactor Antineutrino Anomaly is rejected at more than 99.9% C.L. To allow inclusion of this work into global oscillation analyses and further works, we provide various results of our analysis in digitised form.

  • Relative Spectra of IBD Events for Phase-I+II

    10.17182/hepdata.92323.v2/t1

    Data from Figure 30 – Relative comparison between the estimated rates of IBD events $A_{l,i}$ (for cell $l$ and energy...

  • Exclusion and Sensitivity Contours (two-dimensional method)

    10.17182/hepdata.92323.v2/t2

    Data from Figures 33 and 34 – STEREO exclusion and exclusion sensitivity contours at 95% C.L. for 179 days reactor-on...

  • Exclusion and Sensitivity Contours (raster-scan method)

    10.17182/hepdata.92323.v2/t3

    Data from Figure 34 – STEREO exclusion and exclusion sensitivity contours at 95% C.L. for 179 days reactor-on (phase-I+II) using...

  • Exclusion and Sensitivity Contours (CLs method)

    10.17182/hepdata.92323.v2/t4

    Data from Figure 34 – STEREO exclusion and exclusion sensitivity contours at 95% C.L. for 179 days reactor-on (phase-I+II) using...

  • Delta Chi-squared Map (two-dimensional method)

    10.17182/hepdata.92323.v2/t5

    $\Delta \chi^2$ map of phase-I+II data calculated by the two-dimensional method. To be used in combination with the $\Delta \chi^2_{\text{crit},x}$...

  • Critical Delta Chi-squared Map (two-dimensional method)

    10.17182/hepdata.92323.v2/t6

    The $\Delta \chi^2_{\text{crit},x}$ map accounts for the fact that the $\Delta \chi^2$ values of the oscillation fit do not follow...

  • Delta Chi-squared Map (raster-scan method)

    10.17182/hepdata.92323.v2/t7

    $\Delta \chi^2$ map of phase-I+II data calculated by the raster-scan method. To be used in combination with the $\Delta \chi^2_{\text{crit},x}$...

  • Critical Delta Chi-squared Map (raster-scan method)

    10.17182/hepdata.92323.v2/t8

    The $\Delta \chi^2_{\text{crit},x}$ and $\Delta \chi^2$ values in the raster-scan method serve the same purpose as in the two-dimensional method....

  • Delta Chi-squared Map (CLs method)

    10.17182/hepdata.92323.v2/t9

    $\Delta T$ map of phase-I+II data calculated by the CLs method. To be used in combination with the $\Delta T_{\text{crit},x}$...

  • Critical Delta Chi-squared Map (CLs method)

    10.17182/hepdata.92323.v2/t10

    The $\Delta T_{\text{crit},x}$ and $\Delta T$ values in the CLs method fulfil a similar purpose as the $\Delta \chi^2_{\text{crit},x}$ and...

Version 2 modifications: Version 2 of the supplemental data includes additional exclusion contours and maps for the two-dimensional method and the CLs method.

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