Soviet–American Gallium Experiment
SAGE (Soviet–American Gallium Experiment, or sometimes Russian-American Gallium Experiment) is a collaborative experiment devised by several prominent physicists to measure the solar neutrino flux.
The experiment
editSAGE was devised to measure the radio-chemical solar neutrino flux based on the inverse beta decay reaction, 71Ga 71Ge. The target for the reaction was 50-57 tonnes of liquid gallium metal stored deep (2100 meters) underground at the Baksan Neutrino Observatory in the Caucasus mountains in Russia. The laboratory containing the SAGE-experiment is called gallium-germanium neutrino telescope (GGNT) laboratory, GGNT being the name of the SAGE experimental apparatus. About once a month, the neutrino induced Ge is extracted from the Ga. 71Ge is unstable with respect to electron capture ( days) and, therefore, the amount of extracted germanium can be determined from its activity as measured in small proportional counters.
The experiment had begun to measure the solar neutrino capture rate with a target of gallium metal in December 1989 and continued to run in August 2011 with only a few brief interruptions in the timespan. As of 2013 is the experiment was described as "being continued"[1] with the latest published data from August 2011. As of 2014 it was stated that the SAGE experiment continues the once-a-month extractions.[2] The SAGE experiment continued in 2016.[3] As of 2017, the SAGE-experiment continues.[4]
The experiment has measured the solar neutrino flux in 168 extractions between January 1990 and December 2007. The result of the experiment based on the whole 1990-2007 set of data is 65.4+3.1
−3.0 (stat.) +2.6
−2.8 (syst.) SNU. This represents only 56%-60% of the capture rate predicted by different Standard Solar Models, which predict 138 SNU. The difference is in agreement with neutrino oscillations.
The collaboration has used a 518 kCi 51Cr neutrino source to test the experimental operation. The energy of these neutrinos is similar to the solar 7Be neutrinos and thus makes an ideal check on the experimental procedure. The extractions for the Cr experiment took place between January and May 1995 and the counting of the samples lasted until fall. The result, expressed in terms of a ratio of the measured production rate to the expected production rate, is 1.0±0.15. This indicates that the discrepancy between the solar model predictions and the SAGE flux measurement cannot be an experimental artifact. Also calibrations with a 37Ar neutrino source had been performed.
Baksan Experiment on Sterile Transitions (BEST)
editIn 2014, the SAGE-experiment's GGNT-apparatus (gallium-germanium neutrino telescope) was upgraded to perform a very-short-baseline neutrino oscillation experiment BEST (Baksan Experiment on Sterile Transitions) with an intense artificial neutrino source based on 51Cr.[5] In 2017, the BEST apparatus was completed, but the artificial neutrino source was missing.[6] As of 2018, the BEST experiment was underway.[7] As of 2018, a follow-up experiment BEST-2 where the source would be changed to 65Zn was under consideration.[8] It uses two gallium chambers instead of one, to better determine whether the anomaly could be explained by the distance from the source of the neutrinos[9]
The gallium anomaly
editIn June 2022, the BEST experiment released two papers observing a 20-24% deficit in the production the isotope germanium expected from the reaction , confirming previous results from SAGE and GALLEX on the so called "gallium anomaly" pointing out that a sterile neutrino explanation can be consistent with the data.[10][11][12] Further work have refined the precision for the cross section of the neutrino capture in 2023[13] as well as half-life of in 2024[14] ruling them out as possible explanations for the anomaly.[9]
Members of SAGE
editSAGE is led by the following physicists:
- Vladimir Gavrin (leader of the experiment as of 2017)
- Georgiy Zatsepin (Joint Institute for Nuclear Research, Russia)
- Thomas J. Bowles (Los Alamos)
See also
edit- GALLEX/GNO was the second (of two) large gallium-germanium radiochemical experiment. It was running in 1991-2003.
- Hans Bethe was the architect of the theory of nuclear fusion reactions in stars.
- The University of Washington is playing a major role in the statistical analysis of the SAGE data and in the determination of systematic uncertainties. They are very active in the remaining analysis of the Cr experiment data as well as the solar neutrino data.
References
edit- ^ Gavrin, V. N. (October 2013). "Contribution of gallium experiments to the understanding of solar physics and neutrino physics". Physics of Atomic Nuclei. 76 (10): 1238–1243. Bibcode:2013PAN....76.1238G. doi:10.1134/S106377881309007X. S2CID 122656176.
- ^ "Archived copy" (PDF). Archived from the original (PDF) on 2020-10-25. Retrieved 2018-12-15.
{{cite web}}
: CS1 maint: archived copy as title (link) - ^ "Archived copy" (PDF). Archived from the original (PDF) on 2019-05-31. Retrieved 2019-05-31.
{{cite web}}
: CS1 maint: archived copy as title (link) - ^ "Baksan scales new neutrino heights – CERN Courier". 19 May 2017.
- ^ Gavrin, V.; Cleveland, B.; Danshin, S.; Elliott, S.; Gorbachev, V.; Ibragimova, T.; Kalikhov, A.; Knodel, T.; Kozlova, Yu.; Malyshkin, Yu.; Matveev, V.; Mirmov, I.; Nico, J.; Robertson, R. G. H.; Shikhin, A.; Sinclair, D.; Veretenkin, E.; Wilkerson, J. (2015). "Current status of new SAGE project with 51Cr neutrino source". Physics of Particles and Nuclei. 46 (2): 131. Bibcode:2015PPN....46..131G. doi:10.1134/S1063779615020100. OSTI 1440431. S2CID 120787161.
- ^ "Baksan scales new neutrino heights – CERN Courier". 19 May 2017.
- ^ Babenko, Maxim; Overbye, Dennis (2018-07-16). "The Neutrino Trappers". The New York Times.
- ^ Gavrin, V. N.; Gorbachev, V. V.; Ibragimova, T. V.; Kornoukhov, V. N.; Dzhanelidze, A. A.; Zlokazov, S. B.; Kotelnikov, N. A.; Izhutov, A. L.; Mainskov, S. V.; Pimenov, V. V.; Borisenko, V. P.; Kiselev, K. B.; Tsevelev, M. P. (2018). "On the gallium experiment BEST-2 with a 65Zn source to search for neutrino oscillations on a short baseline". arXiv:1807.02977 [physics.ins-det].
- ^ a b O'Callaghan, Jonathan (2024-07-12). "What Could Explain the Gallium Anomaly?". Quanta Magazine. Retrieved 2024-07-14.
- ^ Laboratory, Los Alamos National (2022-06-18). "Deep Underground Experiment Results Confirm Anomaly: Possible New Fundamental Physics". SciTechDaily. Retrieved 2022-06-22.
- ^ Barinov, V. V.; Cleveland, B. T.; Danshin, S. N.; Ejiri, H.; Elliott, S. R.; Frekers, D.; Gavrin, V. N.; Gorbachev, V. V.; Gorbunov, D. S.; Haxton, W. C.; Ibragimova, T. V. (2022-06-09). "Results from the Baksan Experiment on Sterile Transitions (BEST)". Physical Review Letters. 128 (23): 232501. arXiv:2109.11482. Bibcode:2022PhRvL.128w2501B. doi:10.1103/PhysRevLett.128.232501. PMID 35749172. S2CID 237605431.
- ^ Barinov, V. V.; Danshin, S. N.; Gavrin, V. N.; Gorbachev, V. V.; Gorbunov, D. S.; Ibragimova, T. V.; Kozlova, Yu. P.; Kravchuk, L. V.; Kuzminov, V. V.; Lubsandorzhiev, B. K.; Malyshkin, Yu. M. (2022-06-09). "Search for electron-neutrino transitions to sterile states in the BEST experiment". Physical Review C. 105 (6): 065502. arXiv:2201.07364. Bibcode:2022PhRvC.105f5502B. doi:10.1103/PhysRevC.105.065502. S2CID 246035834.
- ^ Elliott, S. R.; Gavrin, V. N.; Haxton, W. C.; Ibragimova, T. V.; Rule, E. J. (2023-09-25). "Gallium neutrino absorption cross section and its uncertainty". Physical Review C. 108 (3). arXiv:2303.13623. doi:10.1103/PhysRevC.108.035502. ISSN 2469-9985.
- ^ Norman, E. B.; Drobizhev, A.; Gharibyan, N.; Gregorich, K. E.; Kolomensky, Yu. G.; Sammis, B. N.; Scielzo, N. D.; Shusterman, J. A.; Thomas, K. J. (2024-05-30). "Half-life of Ge 71 and the gallium anomaly". Physical Review C. 109 (5). doi:10.1103/PhysRevC.109.055501. ISSN 2469-9985.
Literature
edit- Abdurashitov, J. N.; et al. (2009). "Measurement of the solar neutrino capture rate with gallium metal. III. Results for the 2002–2007 data-taking period". Physical Review C. 80 (1): 015807. arXiv:0901.2200. Bibcode:2009PhRvC..80a5807A. doi:10.1103/PhysRevC.80.015807. S2CID 118782386.
External links
edit- The web page of the experiment in the University of Washington
- Old page (1994) with results of the experiments
- Some results (2001) (in Russian)
- Hans Bethe talking about SAGE (video)
- SAGE experiment record on INSPIRE-HEP