MiniBooNE is a Cherenkov detector experiment at

Fermilab Fermi National Accelerator Laboratory (Fermilab), located in Batavia, Illinois, near Chicago, is a United States Department of Energy United States Department of Energy National Labs, national laboratory specializing in high-energy particle phys ...

designed to observe

neutrino oscillation Neutrino oscillation is a quantum mechanics, quantum mechanical phenomenon in which a neutrino created with a specific lepton lepton number, family number ("lepton flavor": electron, muon, or tau lepton, tau) can later be Quantum measurement, mea ...

s (BooNE is an acronym for the Booster

Neutrino A neutrino ( ; denoted by the Greek letter ) is an elementary particle that interacts via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass is so small ('' -ino'') that i ...

Experiment An experiment is a procedure carried out to support or refute a hypothesis, or determine the efficacy or likelihood of something previously untried. Experiments provide insight into cause-and-effect by demonstrating what outcome occurs whe ...

). A

neutrino A neutrino ( ; denoted by the Greek letter ) is an elementary particle that interacts via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass is so small ('' -ino'') that i ...

beam consisting primarily of

muon neutrino The muon neutrino is an elementary particle which has the symbol and zero electric charge. Together with the muon it forms the second generation of leptons, hence the name muon neutrino. It was discovered in 1962 by Leon Lederman, Melvin Schwa ...

s is directed at a detector filled with 800 tons of

mineral oil Mineral oil is any of various colorless, odorless, light mixtures of higher alkanes from a mineral source, particularly a distillate of petroleum, as distinct from usually edible vegetable oils. The name 'mineral oil' by itself is imprecise, ...

(ultrarefined methylene compounds) and lined with 1,280 photomultiplier tubes. An excess of electron neutrino events in the detector would support the neutrino oscillation interpretation of the LSND (Liquid Scintillator Neutrino Detector) result. MiniBooNE started collecting data in 2002 and was still running in 2017. In May 2018, physicists of the MiniBooNE experiment reported a possible signal indicating the existence of sterile neutrinos.

History and motivation

Experimental observation of solar neutrinos and atmospheric neutrinos provided evidence for

s, implying that neutrinos have masses. Data from the LSND experiment at

Los Alamos National Laboratory Los Alamos National Laboratory (often shortened as Los Alamos and LANL) is one of the sixteen research and development Laboratory, laboratories of the United States Department of Energy National Laboratories, United States Department of Energy ...

are controversial since they are not compatible with the oscillation parameters measured by other neutrino experiments in the framework of the

Standard Model The Standard Model of particle physics is the Scientific theory, theory describing three of the four known fundamental forces (electromagnetism, electromagnetic, weak interaction, weak and strong interactions – excluding gravity) in the unive ...

. Either there must be an extension to the

, or one of the experimental results must have a different explanation. Moreover, the KARMEN experiment in Karlsruhe examined a ow energyregion similar to the LSND experiment, but saw no indications of neutrino oscillations. This experiment was less sensitive than LSND, and both could be right. Cosmological data can provide an indirect but rather model-dependent bound to the mass of sterile neutrinos, such as the ''m''_s < () at 95% (99.9%) confidence limit given by Dodelson ''et al''. However, cosmological data can be accommodated within models with different assumptions, such as that by Gelmini ''et al.'' MiniBooNE was designed to unambiguously verify or refute the LSND controversial result in a controlled environment.

2007

: After the beam was turned on in 2002, the first results came in late March 2007, and showed no evidence for

electron neutrino The electron neutrino () is an elementary particle which has zero electric charge and a spin of . Together with the electron, it forms the first generation of leptons, hence the name ''electron neutrino''. It was first hypothesized by Wolfga ...

oscillations in the LSND ow energyregion, refuting a simple 2-neutrino oscillation interpretation of the LSND results. More advanced analyses of their data are currently being undertaken by the MiniBooNE collaboration; early indications are pointing towards the existence of the sterile neutrino, an effect interpreted by some physicists to be hinting of the existence of the bulk or Lorentz violation.

2008

: A collaboration of MiniBooNE with other scientists a new experiment, called MicroBooNE, was designed to further investigate sterile neutrinos.

2018

: With a study published on

arXiv arXiv (pronounced as "archive"—the X represents the Chi (letter), Greek letter chi ⟨χ⟩) is an open-access repository of electronic preprints and postprints (known as e-prints) approved for posting after moderation, but not Scholarly pee ...

, the collaboration announced that the finding of neutrino oscillations at MiniBooNE are confirmed at a 4.8 sigma level and, when combined with data at LSND, at a 6.1 sigma level. This hints at the detection of sterile neutrinos and a significant deviation from known physics. The implication of the paper is that some of the muon neutrinos are flipping to sterile neutrinos before switching identity again to electron neutrinos.Has US physics lab found a new particle?
Paul Rincon, ''BBC News''. 6 June 2018.

References

External links

and
MiniBooNE website

MiniBooNE publications

Experiment detailsAn informal discussion of the experiment and initial resultsExperiment Nixes Fourth Neutrino (April 2007 Scientific American)Dimensional Shortcuts - evidence for sterile neutrino; (August 2007; Scientific American)
{{coords, 41.8380722, -88.269513, display=title Accelerator neutrino experiments Fermilab Fermilab experiments Fixed-target experiments