Results from the Baksan Experiment on Sterile Transitions (BEST)

Journal Article · Thu Jun 09 00:00:00 EDT 2022 · Physical Review Letters

DOI:https://doi.org/10.1103/PhysRevLett.128.232501· OSTI ID:2871121

Barinov, V. V. ^[1]; Cleveland, B. T. ^[2]; Danshin, S. N. ^[1]; Ejiri, H. ^[3]; Elliott, S. R. ^[4]; Frekers, D. ^[5]; Gavrin, V. N. ^[1]; Gorbachev, V. V. ^[1]; Gorbunov, D. S. ^[1]; Haxton, W. C. ^[6]; Ibragimova, T. V. ^[1]; Kim, I. ^[4]; Kozlova, Yu. P. ^[1]; Kravchuk, L. V. ^[1]; Kuzminov, V. V. ^[1]; Lubsandorzhiev, B. K. ^[1]; Malyshkin, Yu. M. ^[1]; Massarczyk, R. ^[4]; Matveev, V. A. ^[7]; Mirmov, I. N. ^[1] ; Nico, J. S. ^[8]; Petelin, A. L. ^[9]; Robertson, R. G. H. ^[10]; Sinclair, D. ^[11]; Shikhin, A. A. ^[1]; Tarasov, V. A. ^[9]; Trubnikov, G. V. ^[12]; Veretenkin, E. P. ^[1]; Wilkerson, J. F. ^[13]; Zvir, A. I. ^[9]

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1. Institute for Nuclear Research of the Russian Academy of Sciences, Moscow (Russia)
2. SNOLAB, Sudbury, ON (Canada)
3. Osaka University (Japan)
4. Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
5. Westfälische Wilhelms-Universität Munster (Germany)
6. Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); University of California, Berkeley, CA (United States)
7. Joint Institute for Nuclear Research (JINR) Joliot-Curie, Moscow Region (Russia)
8. National Institute of Standards and Technology, Gaithersburg, MD (United States)
9. JSC “State Scientific Center Research Institute of Atomic Reactors,” Dimitrovgrad (Russia)
10. University of Washington, Seattle, WA (United States)
11. Carleton University, Ottawa (Canada)
12. Joint Institute for Nuclear Research (JINR) Joliot-Curie, Moscow (Russia)
13. University of North Carolina, Chapel Hill, NC (United States); Triangle Universities Nuclear Laboratory, Durham, NC (United States)

The Baksan Experiment on Sterile Transitions (BEST) was designed to investigate the deficit of electron neutrinos 𝜈𝑒 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 𝜈𝑒 and sterile neutrino (𝜈_𝑠) states. A 3.414-MCi ⁵¹Cr 𝜈_𝑒 source was placed at the center of two nested Ga volumes and measurements were made of the production of ⁷¹Ge through the charged current reaction, ⁷¹Ga ⁢(𝜈_𝑒,𝑒⁻)^⁢71Ge, at two average distances. The measured production rates for the inner and the outer targets, respectively, are [54.9$$^{+2.5}_{−2.4}$$⁢(stat) ± 1.4⁢(syst)] and [55.6$$^{+2.7}_{−2.6}$$⁢(stat) ± 1.4⁢(syst)] atoms of ⁷¹Ge/𝑑. The ratio (𝑅) of the measured rate of ⁷¹Ge production at each distance to the expected rate from the known cross section and experimental efficiencies are 𝑅_in = 0.79 ± 0.05 and 𝑅_out = 0.77 ± 0.05. The ratio of the outer to the inner result is 0.97 ± 0.07, which is consistent with unity within uncertainty. The rates at each distance were found to be similar, but 20%–24% lower than expected, thus reaffirming the anomaly. Furthermore, these results are consistent with 𝜈_𝑒 → 𝜈_𝑠 oscillations with a relatively large Δ⁢𝑚² (>0.5 eV²) and mixing sin²⁡2⁢𝜃 (≈ 0.4).

• Research Organization: University of California, Berkeley, CA (United States)
• Sponsoring Organization: USDOE; Ministry of Science and Higher Education of Russian Federation
• Grant/Contract Number: SC0004658
• OSTI ID: 2871121
• Alternate ID(s): OSTI ID: 2008274; OSTI ID: 1905764; OSTI ID: 1907282; OSTI ID: 1907798
• Journal Information: Physical Review Letters, Journal Name: Physical Review Letters Journal Issue: 23 Vol. 128; ISSN 1079-7114; ISSN 0031-9007
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

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Neutrino oscillations