MiniBooNE is a Cherenkov detector experiment at

Fermilab Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a United States Department of Energy national laboratory specializing in high-energy particle physics. Since 2007, Fermilab has been operat ...

designed to observe neutrino oscillations (BooNE is an acronym for the

Booster Booster may refer to: Amusement rides * Booster (Fabbri ride), a pendulum ride * Booster (HUSS ride), an evolution of the Breakdance ride * Booster (KMG ride), a pendulum ride Arts, entertainment, and media Fictional characters * Booster, a cha ...

Neutrino A neutrino ( ; denoted by the Greek letter ) is a fermion (an elementary particle with spin of ) that interacts only via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass ...

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 Causality, cause-and-effect by demonstrating what outcome oc ...

). A

neutrino A neutrino ( ; denoted by the Greek letter ) is a fermion (an elementary particle with spin of ) that interacts only via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass ...

beam Beam may refer to: Streams of particles or energy *Light beam, or beam of light, a directional projection of light energy **Laser beam *Particle beam, a stream of charged or neutral particles **Charged particle beam, a spatially localized grou ...

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 Schwar ...

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 Photomultiplier tubes (photomultipliers or PMTs for short) are extremely sensitive detectors of light in the ultraviolet, visible, and near-infrared ranges of the electromagnetic spectrum. They are members of the class of vacuum tubes, more speci ...

. An excess of electron neutrino

events Event may refer to: Gatherings of people * Ceremony, an event of ritual significance, performed on a special occasion * Convention (meeting), a gathering of individuals engaged in some common interest * Event management, the organization of ev ...

in the detector would support the neutrino oscillation interpretation of the

LSND The Liquid Scintillator Neutrino Detector (LSND) was a scintillation counter at Los Alamos National Laboratory that measured the number of neutrinos being produced by an accelerator neutrino source. The LSND project was created to look for evidence ...

(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 Sterile neutrinos (or inert neutrinos) are hypothetical particles (neutral leptons – neutrinos) that are believed to interact only via gravity and not via any of the other fundamental interactions of the Standard Model. The term ''sterile neutrin ...

History and motivation

Experimental observation of

solar neutrino A solar neutrino is a neutrino originating from nuclear fusion in the Sun's core, and is the most common type of neutrino passing through any source observed on Earth at any particular moment. Neutrinos are elementary particles with extremely smal ...

s and atmospheric neutrinos provided evidence for neutrino oscillations, 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 laboratories of the United States Department of Energy (DOE), located a short distance northwest of Santa Fe, New Mexico, ...

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 theory describing three of the four known fundamental forces (electromagnetism, electromagnetic, weak interaction, weak and strong interactions - excluding gravity) in the universe and classifying a ...

. 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

, and both could be right. Cosmological data can provide an indirect but rather model-dependent bound to the mass of

sterile neutrino Sterile neutrinos (or inert neutrinos) are hypothetical particles (neutral leptons – neutrinos) that are believed to interact only via gravity and not via any of the other fundamental interactions of the Standard Model. The term ''sterile neutrin ...

s, 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 Wolfgang Pauli ...

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

, an effect interpreted by some physicists to be hinting of the existence of the bulk or

Lorentz violation In relativistic physics, Lorentz symmetry or Lorentz invariance, named after the Dutch physicist Hendrik Lorentz, is an equivalence of observation or observational symmetry due to special relativity implying that the laws of physics stay the same ...

2008

: A collaboration of MiniBooNE with other scientists a new experiment, called

MicroBooNE MicroBooNE is a liquid argon time projection chamber (LArTPC) at Fermilab in Batavia, Illinois. It is located in the Booster Neutrino Beam (BNB) beamline where neutrinos are produced by colliding protons from Fermilab's booster-accelerator on a b ...

, was designed to further investigate sterile neutrinos.

2018

: With a study published on

arXiv arXiv (pronounced "archive"—the X represents the 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 peer review. It consists of ...

, 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