Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Results from the Baksan Experiment on Sterile Transitions (BEST)



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


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).
Physical Review Letters


neutrino, neutrino oscillations, sterile neutrinos, radiochemical experiment


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],, (Accessed February 26, 2024)
Created June 9, 2022, Updated December 1, 2022