Results from the Baksan Experiment on Sterile Transitions (BEST)

Published

June 9, 2022

Author(s)

Jeffrey S. Nico, V Barinov, Bruce Cleveland, S Danshin, H Ejiri, Steve Elliott, D Frekers, Vladimir Gavrin, Valery Gorbachev, D Gorbunov, Wick Haxton, Tanya Ibragimova, I Kim, Yu Kozlova, L Kravchuk, V Kuzminov, B Lubsandorzhiev, Yu Malyshkin, R Massarczyk, Victor Matveev, Ilya Mirmov, A Petelin, R Robertson, D Sinclair, A Shikhin, V Tarasov, G Trubnikov, E Veretenkin, John Wilkerson, A Zvir

Abstract

The Baksan Experiment on Sterile Transitions (BEST) was designed to investigate the deficit of electron neutrinos, nu_e, observed in previous gallium-based radiochemical measurements with high-intensity neutrino sources, commonly referred to as the gallium anomaly, which could be interpreted as evidence for oscillations between nu_e and sterile neutrino (nu_s) states. A 3.414-MCi Cr-51 nu_e source was placed at the center of two nested Ga volumes and measurements were made of the production of Ge-71 through the charged current reaction, 71Ga}(nu_e ,e^-)71Ge, at two distances. The measured production rates for the inner and the outer targets respectively are (54.9^+2.5}_-2.4}(stat) \pm1.4 (syst})) and (55.6^+2.7}_-2.6}(stat} \pm1.4 (syst})) atoms of 71Ge/d. The ratio (R) of the measured rate of Ge-71 production at each distance to the expected rate from the known cross section and experimental efficiencies are R_in=0.791 \pm 0.055 and R_out= 0.766 \pm 0.055. The ratio of the outer to the inner result is 0.97 \pm 0.09, which is consistent with unity within uncertainty. The rates at each distance were found to be similar, but 20-24% lower than expected, thus confirming the anomaly. These results are consistent with nu_e -> nu_s oscillations with a relatively large
\Δ m^2 (>1 eV^2) and mixing sin^2 2\theta (\approx 0.4).

Citation

Physical Review Letters

Volume

128

Pub Type

Journals

Download Paper

https://doi.org/10.1103/PhysRevLett.128.232501

Local Download

Keywords

neutrino, neutrino oscillations, sterile neutrinos, radiochemical experiment

Citation

Nico, J. , Barinov, V. , Cleveland, B. , Danshin, S. , Ejiri, H. , Elliott, S. , Frekers, D. , Gavrin, V. , Gorbachev, V. , Gorbunov, D. , Haxton, W. , Ibragimova, T. , Kim, I. , Kozlova, Y. , Kravchuk, L. , Kuzminov, V. , Lubsandorzhiev, B. , Malyshkin, Y. , Massarczyk, R. , Matveev, V. , Mirmov, I. , Petelin, A. , Robertson, R. , Sinclair, D. , Shikhin, A. , Tarasov, V. , Trubnikov, G. , Veretenkin, E. , Wilkerson, J. and Zvir, A. (2022), Results from the Baksan Experiment on Sterile Transitions (BEST), Physical Review Letters, [online], https://doi.org/10.1103/PhysRevLett.128.232501, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=933326 (Accessed October 8, 2025)