Results of deep underground experiments confirm anomaly: possible new fundamental physics

Plasma particle physics concept art

New outcomes from the Baksan Experiment on Sterile Transformations (BEST) affirm an anomaly that signifies a brand new bodily potential.

Sterile neutrinos, Fundamentals of physics amongst explanations of anomalous outcomes.

The brand new scientific findings affirm an anomaly seen in earlier experiments, which can level to a brand new as-yet-confirmed elementary particle, the sterile neutrino, or level to the necessity for a brand new rationalization for a side of Normal Mannequin Physics, such because the neutrino cross-section, which was first measured 60 years in the past. Los Alamos Nationwide Laboratory is the lead US establishment collaborating on the Baksan Experiment on Sterile Transformations (BEST), the outcomes of which had been just lately printed in journals. Bodily Assessment Letters And the bodily evaluation c.

“The outcomes are very thrilling,” stated Steve Elliott, a senior analyst on one of many groups evaluating the info and a member of the physics division at Los Alamos. “This actually reconfirms the anomalies we noticed in earlier experiments. However what this implies isn’t clear. There are actually conflicting outcomes about sterile neutrinos. If the outcomes point out a misunderstanding of fundamental nuclear or atomic physics, that will even be attention-grabbing.” Different members of the Los Alamos workforce embrace Ralph Masarczyk and Enuk Kim.

best gallium target

Positioned deep underground on the Baksan Neutrino Observatory within the Caucasus Mountains in Russia, the finished goal of two gallium areas, left, comprises an inside and an outer reservoir of gallium, which is irradiated by an electron neutrino supply. Credit score: AA Shikhin

Greater than a mile underground on the Baksan Neutrino Observatory within the Russian Caucasus Mountains 26 radioactive disks of chromium 51, a synthetic radioactive isotope of chromium and a 3.4 megapicurie supply of electron neutrinos, are finest used for gallium inside and outer tank radiation, gentle materials, silver metallic Additionally in earlier experiments, though beforehand it was utilized in a single tank. The response between the electron neutrinos of chromium 51 and gallium produces the isotope germanium 71.

The measured charge of manufacturing of germanium-71 was 20-24% decrease than anticipated primarily based on theoretical modeling. This discrepancy is in keeping with anomalies seen in earlier experiments.

BEST relies on the photo voltaic neutrino experiment, the Soviet-American Gallium Experiment (SAGE), to which Los Alamos Nationwide Laboratory was a serious contributor, starting within the late Eighties. That experiment additionally used high-density gallium and neutrino sources. Outcomes from that experiment and others indicated a deficit in electron neutrinos – a discrepancy between anticipated and precise outcomes that has come to be often called the “gallium anomaly”. The reason for the deficit may very well be proof of oscillations between electron neutrinos and sterile neutrino states.

chrome discs

An array of 26 radioactive chromium-51 discs is the supply of the electron neutrinos that work together with gallium and produce germanium-71 at charges that may be measured towards anticipated charges. Credit score: AA Shikhin

The identical anomaly was repeated in the perfect experiment. Doable explanations once more embrace oscillation in a sterile neutrino. A hypothetical particle could make up a major a part of darkish matter, a potential type of matter believed to make up the overwhelming majority of the bodily universe. This interpretation may have additional testing, as a result of the measurement for every tank was almost the identical, albeit lower than anticipated.

Different explanations for the anomaly embrace the chance that there’s a misunderstanding within the theoretical enter to the experiment – that physics itself requires reformulation. Elliott factors out that the cross-section of the electron neutrino has not beforehand been measured at these energies. For instance, the theoretical entry for the measurement of the cross part, which is tough to substantiate, is the electron density within the atomic nucleus.

The experiment’s methodology was fastidiously reviewed to make sure that errors didn’t happen in facets of the analysis, reminiscent of radiation supply placement or counting system operations. Future iterations of the experiment, if carried out, could embrace a unique radiation supply with increased vitality, longer half-life, and sensitivity to shorter oscillation wavelengths.

References:

“Outcomes of the Baksan Experiment on Sterile Transformations (Higher)” By V.V. Barinov et al., 9 Jun 2022, Obtainable right here. Bodily Assessment Letters.
DOI: 10.1103/ PhysRevLett.128.232501

“Looking for electron-neutrino transitions to sterile states in the perfect experiment” By V. V. Barinov et al., 9 Jun 2022, Obtainable right here. bodily evaluation c.
DOI: 10.1103/ PhysRevC.105.065502

Funding: Division of Vitality, Workplace of Science, Workplace of Nuclear Physics.