MiniBooNE

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The interior of the MiniBooNE detector. MiniBooNE phototubes.jpg
The interior of the MiniBooNE detector.

MiniBooNE is a Cherenkov detector experiment at Fermilab designed to observe neutrino oscillations (BooNE is an acronym for the Booster Neutrino Experiment). A neutrino beam consisting primarily of muon neutrinos is directed at a detector filled with 800 tons of mineral oil (ultrarefined methylene compounds) and lined with 1,280 photomultiplier tubes. [1] An excess of electron neutrino events in the detector would support the neutrino oscillation interpretation of the LSND (Liquid Scintillator Neutrino Detector) result.

Contents

MiniBooNE started collecting data in 2002 [2] and was still running in 2017. [3] In May 2018, physicists of the MiniBooNE experiment reported a possible signal indicating the existence of sterile neutrinos. [4]

History and motivation

Experimental observation of solar neutrinos and atmospheric neutrinos provided evidence for neutrino oscillations, implying that neutrinos have masses. Data from the LSND experiment at Los Alamos National Laboratory are controversial since they are not compatible with the oscillation parameters measured by other neutrino experiments in the framework of the Standard Model. Either there must be an extension to the Standard Model, or one of the experimental results must have a different explanation. Moreover, the KARMEN experiment in Karlsruhe [5] examined a [low energy] region 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 ms < 0.26 eV (0.44 eV) at 95% (99.9%) confidence limit given by Dodelson et al. [6] However, cosmological data can be accommodated within models with different assumptions, such as that by Gelmini et al. [7]

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 muon neutrino to electron neutrino oscillations in the LSND [low energy] region, refuting a simple 2-neutrino oscillation interpretation of the LSND results. [8] 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, [9] an effect interpreted by some physicists to be hinting of the existence of the bulk [10] or Lorentz violation. [11]

2008

A collaboration of MiniBooNE with other scientists a new experiment, called MicroBooNE, was designed to further investigate sterile neutrinos. [12]

2018

With a study published on arXiv, [3] 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. [13] The implication of the paper is that some of the muon neutrinos are flipping to sterile neutrinos before switching identity again to electron neutrinos. [14]

Related Research Articles

Neutrino Elementary particle with extremely low mass that interacts only via the weak force and gravity

A neutrino is a fermion that interacts only 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 it was long thought to be zero. The rest mass of the neutrino is much smaller than that of the other known elementary particles excluding massless particles. The weak force has a very short range, the gravitational interaction is extremely weak, and neutrinos do not participate in the strong interaction. Thus, neutrinos typically pass through normal matter unimpeded and undetected.

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 of neutrino oscillation, and its results conflict with the standard model expectation of only three neutrino flavors, when considered in the context of other solar and atmospheric neutrino oscillation experiments. Cosmological data bound the mass of the sterile neutrino to ms < 0.26eV (0.44eV) at 95% (99.9%) confidence limit, excluding at high significance the sterile neutrino hypothesis as an explanation of the LSND anomaly. The controversial LSND result was tested by the MiniBooNE experiment at Fermilab which has found similar evidence for oscillations. The hint is currently undergoing further tests at MicroBooNE at Fermilab.

KARMEN, a detector associated with the ISIS synchrotron at the Rutherford Appleton Laboratory. Neutrinos for study are supplied via the decay of pions produced when a proton beam strikes a target. It operated from 1990 until March 2001, observing the appearance and disappearance of electron neutrinos. KARMEN searched for neutrino oscillations, with implications for the existence of sterile neutrinos.

Sterile neutrinos are hypothetical particles that are believed to interact only via gravity and not via any of the other fundamental interactions of the Standard Model. The term sterile neutrino is used to distinguish them from the known active neutrinos in the Standard Model, which carry an isospin charge of ±+1/ 2  under the weak interaction. It typically refers to neutrinos with right-handed chirality, which may be added to the Standard Model. Particles that possess the quantum numbers of sterile neutrinos and masses great enough such that they do not interfere with the current theory of Big Bang Nucleosynthesis are often called neutral heavy leptons (NHLs) or heavy neutral leptons (HNLs).

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MINOS

Main injector neutrino oscillation search (MINOS) was a particle physics experiment designed to study the phenomena of neutrino oscillations, first discovered by a Super-Kamiokande (Super-K) experiment in 1998. Neutrinos produced by the NuMI beamline at Fermilab near Chicago are observed at two detectors, one very close to where the beam is produced, and another much larger detector 735 km away in northern Minnesota.

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T2K is a particle physics experiment studying the oscillations of the accelerator neutrinos. The experiment is conducted in Japan by the international cooperation of about 500 physicists and engineers with over 60 research institutions from several countries from Europe, Asia and North America and it is a recognized CERN experiment (RE13). T2K collected data within its first phase of operation from 2010 till 2021. The second phase of data taking (T2K-II) is expected to start in 2023 and last until commencement of the successor of T2K – the Hyper-Kamiokande experiment in 2027.

SciBooNE

SciBar Booster Neutrino Experiment (SciBooNE), was a neutrino experiment located at the Fermi National Accelerator Laboratory (Fermilab) in the USA. It observed neutrinos of the Fermilab Booster Neutrino Beam (BNB) that are produced when protons from the Fermilab Booster-accelerator were made to hit a beryllium target; this led to the production of many short-lived particles that decayed into neutrinos. The SciBooNE detector was located some 100 meters downrange from the beryllium target, with a 50 meter decay-volume and absorber combined with 50 meters of solid ground between the target and the detector to absorb other particles than neutrinos. The neutrino-beam continued through SciBooNE and ground to the MiniBooNE-detector, located some 540 meters downrange from the target.

Borexino

Borexino is a particle physics experiment to study low energy (sub-MeV) solar neutrinos. The detector is the world's most radio-pure liquid scintillator calorimeter. It is placed within a stainless steel sphere which holds the photomultiplier tubes (PMTs) used as signal detectors and is shielded by a water tank to protect it against external radiation and tag incoming cosmic muons that manage to penetrate the overburden of the mountain above.

Lorentz-violating neutrino oscillation refers to the quantum phenomenon of neutrino oscillations described in a framework that allows the breakdown of Lorentz invariance. Today, neutrino oscillation or change of one type of neutrino into another is an experimentally verified fact; however, the details of the underlying theory responsible for these processes remain an open issue and an active field of study. The conventional model of neutrino oscillations assumes that neutrinos are massive, which provides a successful description of a wide variety of experiments; however, there are a few oscillation signals that cannot be accommodated within this model, which motivates the study of other descriptions. In a theory with Lorentz violation, neutrinos can oscillate with and without masses and many other novel effects described below appear. The generalization of the theory by incorporating Lorentz violation has shown to provide alternative scenarios to explain all the established experimental data through the construction of global models.

The K2K experiment was a neutrino experiment that ran from June 1999 to November 2004. It used muon neutrinos from a well-controlled and well-understood beam to verify the oscillations previously observed by Super-Kamiokande using atmospheric neutrinos. This was the first positive measurement of neutrino oscillations in which both the source and detector were fully under experimenters' control. Previous experiments relied on neutrinos from the Sun or from cosmic sources. The experiment found oscillation parameters which were consistent with those measured by Super-Kamiokande.

Antonio Ereditato Italian physicist

Antonio Ereditato is an Italian physicist, Visiting Professor at the University of Yale, USA and Emeritus professor at the University of Bern, Switzerland, where he has been Director of the Laboratory for High Energy Physics from 2006 to 2020. He carried out research activities in the field of experimental neutrino physics, of weak interactions and strong interactions with experiments conducted at CERN, in Japan, at Fermilab in United States and at the LNGS in Italy. Ereditato has accomplished several R&D studies on particle detectors: wire chambers, calorimeters, time projection chambers, nuclear emulsions, detectors for medical applications.

Modern searches for Lorentz violation Overview about the modern searches for Lorentz violation

Modern searches for Lorentz violation are scientific studies that look for deviations from Lorentz invariance or symmetry, a set of fundamental frameworks that underpin modern science and fundamental physics in particular. These studies try to determine whether violations or exceptions might exist for well-known physical laws such as special relativity and CPT symmetry, as predicted by some variations of quantum gravity, string theory, and some alternatives to general relativity.

Measurements of neutrino speed have been conducted as tests of special relativity and for the determination of the mass of neutrinos. Astronomical searches investigate whether light and neutrinos emitted simultaneously from a distant source are arriving simultaneously on Earth. Terrestrial searches include time of flight measurements using synchronized clocks, and direct comparison of neutrino speed with the speed of other particles.

Accelerator Neutrino Neutron Interaction Experiment Water Cherenkov detector experiment

The Accelerator Neutrino Neutron Interaction Experiment (ANNIE) is a proposed water Cherenkov detector experiment designed to examine the nature of neutrino interactions. This experiment will study phenomena like proton decay, and neutrino oscillations, by analyzing neutrino interactions in gadolinium-loaded water and measuring their neutron yield. Neutron Tagging plays an important role in background rejection from atmospheric neutrinos. By implementing early prototypes of LAPPDs, high precision timing is possible. The suggested location for ANNIE is the SciBooNE hall on the Booster Neutrino Beam associated with the MiniBooNE experiment. The neutrino beam originates in Fermilab where The Booster delivers 8 GeV protons to a beryllium target producing secondary pions and kaons. These secondary mesons decay to produce a neutrino beam with an average energy of around 800 MeV. ANNIE will begin installation in the summer of 2015. Phase I of ANNIE, mapping the neutron background, completed in 2017. The detector is being upgraded for full science operation which is expected to begin late 2018.

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 beryllium target; this produces many short-lived particles that decay into neutrinos. The neutrinos pass through solid ground, through another experiment called ANNIE, then solid ground, then through the Short Baseline Near Detector, then ground again before it arrives at the MicroBooNE detector 470 meters downrange from the target. After MicroBooNE the neutrinos continue to the MiniBooNE detector and to the ICARUS detector. MicroBooNE is also exposed to the neutrino beam from the Main Injector (NuMI) which enter the detector at a different angle.

The STEREO experiment investigates the possible oscillation of neutrinos from a nuclear reactor into light so-called sterile neutrinos. It is located at the Institut Laue–Langevin (ILL) in Grenoble, France. The experiment started operating and taking data in November 2016.

An accelerator neutrino is a human-generated neutrino or antineutrino obtained using particle accelerators, in which beam of protons is accelerated and collided with a fixed target, producing mesons which then decay into neutrinos. Depending on the energy of the accelerated protons and whether mesons decay in flight or at rest it is possible to generate neutrinos of a different flavour, energy and angular distribution. Accelerator neutrinos are used to study neutrino interactions and neutrino oscillations taking advantage of high intensity of neutrino beams, as well as a possibility to control and understand their type and kinematic properties to a much greater extent than for neutrinos from other sources.

Jocelyn Monroe American experimental particle physicist

Jocelyn Monroe is an American experimental particle physicist who is a Professor at Royal Holloway, University of London. Her research considers the development of novel detectors as part of the search for dark matter. In 2016 she was honoured with the Breakthrough Prize in Fundamental Physics for her work on the Sudbury Neutrino Observatory.

References

  1. ↑ "Detector". MiniBooNE Experiment Details. Fermilab . Retrieved 2015-12-07.
  2. ↑ "MiniBooNE website".
  3. 1 2 The MiniBooNE Collaboration (May 2018). "Significant Excess of Electronlike Events in the MiniBooNE Short-Baseline Neutrino Experiment". Physical Review Letters. 121 (22): 221801. arXiv: 1805.12028 . Bibcode:2018PhRvL.121v1801A. doi:10.1103/PhysRevLett.121.221801. PMID   30547637. S2CID   53999758.
  4. ↑ June 2018, Rafi Letzter 01 (2018-06-01). "A Major Physics Experiment Just Detected a Particle That Shouldn't Exist". livescience.com. Retrieved 2021-09-18.
  5. ↑ "KARMEN experiment" (Press release). 3 August 2011. Archived from the original on 5 January 2013.
  6. ↑ S. Dodelson; A. Melchiorri; A. Slosar (2006). "Is cosmology compatible with sterile neutrinos?". Physical Review Letters . 97 (4): 04301. arXiv: astro-ph/0511500 . Bibcode:2006PhRvL..97d1301D. doi:10.1103/PhysRevLett.97.041301. PMID   16907563. S2CID   18263443.
  7. ↑ G. Gelmini; S. Palomares-Ruiz & S. Pascoli (2004). "Low reheating temperature and the visible sterile neutrino". Physical Review Letters . 93 (8): 081302. arXiv: astro-ph/0403323 . Bibcode:2004PhRvL..93h1302G. doi:10.1103/PhysRevLett.93.081302. PMID   15447171. S2CID   13111683.
  8. ↑ A. A. Aguilar-Arevalo; et al. (MiniBooNE Collaboration) (2007). "A Search for Electron Neutrino Appearance at the Δm2 ~ 1 eV2 Scale". Physical Review Letters . 98 (23): 231801. arXiv: 0704.1500 . Bibcode:2007PhRvL..98w1801A. doi:10.1103/PhysRevLett.98.231801. PMID   17677898. S2CID   119315296.
  9. ↑ M. Alpert (August 2007). "Dimensional Shortcuts". Scientific American . Archived from the original on 2013-01-24. Retrieved 2007-07-23.
  10. ↑ H. Päs; S. Pakvasa; T.J. Weiler (2007). "Shortcuts in extra dimensions and neutrino physics". AIP Conference Proceedings . 903: 315–318. arXiv: hep-ph/0611263 . Bibcode:2007AIPC..903..315P. doi:10.1063/1.2735188. S2CID   6745718.
  11. ↑ T. Katori; V.A. Kostelecky; R. Tayloe (2006). "Global three-parameter model for neutrino oscillations using Lorentz violation". Physical Review D . 74 (10): 105009. arXiv: hep-ph/0606154 . Bibcode:2006PhRvD..74j5009K. doi:10.1103/PhysRevD.74.105009. S2CID   6459548.
  12. ↑ M. Alpert (September 2008). "Fermilab Looks for Visitors from Another Dimension". Scientific American . Retrieved 2008-09-23.
  13. ↑ Letzter, Rafi (1 June 2018). "A Major Physics Experiment Just Detected A Particle That Shouldn't Exist". LiveScience . Retrieved 4 June 2018.
  14. ↑ Has US physics lab found a new particle?. Paul Rincon, BBC News. 6 June 2018.

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