(Wolfgang Pauli proposed the existence of a neutral, light-weight particle capable of preserving the conservation of energy principle)
Neutrino Science has been studied for over 90 years
They come in three main flavors and may switch between them as they move. They are undetectable and unaffected by ordinary stuff. In the time it would take you to read this phrase, trillions of them pass through your body. But don’t worry, they’re completely harmless. They are produced, among other things, by the sun, within the Globe, at nuclear power plants, by exploding stars, and by cosmic radiation interacting with the Earth’s atmosphere.
While many past and contemporary experiments have taught us a lot about them, there are still a lot of unanswered questions and riddles in science. A series of bold new experiments aims to close many of the most significant gaps in our understanding.
Each of their three types has an antimatter counterpart, and it’s unclear whether these antimatter counterparts are largely the same as their normal forms. Knowing the answer to this question could help clarify whether they played a significant role in the universe’s abundance of matter vs. antimatter.
We realize they have three various masses as well, but we don’t know which is the lightest or heaviest of the three.
They were identified in 1956, yet 90 years earlier, on December 4, 1930, they were postulated to exist.
“They” are subatomic particles known as neutrinos, and scientists all over the world has a rich history of having participated in neutrino experiments and scientific breakthroughs in locations ranging from a 1.3-mile-deep nickel mine in Ontario, Canada, to an underground scientific site near a nuclear power complex northeast of Hong Kong.
Austrian scientist named Wolfgang Pauli proposed the existence of these particles in a letter dated Dec. 4, 1930, describing them as a “almost improbable” and “desperate remedy” for preserving a fundamental scientific law while trying to explain an apparent energy surplus in nuclear decay processes in some atomic nuclei. Physicist Enrico Fermi called these hypothetical particles “neutrinos” – Italian for “little neutral ones” – in 1934, after Pauli referred to them as “neutrons.”
To commemorate how far neutrino research has progressed in the 90 years after Pauli predicted the particle, Neutrino Science has compiled a list of some of the most important neutrino experiment results to which scientists from all over the world have participated.
Institutions that have been involved in a variety of experiments and accomplishments:
Canada’s Sudbury Neutrino Observatory (SNO)
SNO was the first to show that neutrinos produced by the sun may change flavors, basically morphing between three different varieties. It was a Nobel Laureate-winning discovery. A 40-foot-diameter spherical acrylic detector was suspended from the roof of an underground cavern at an active mining site in Ontario, Canada, for the experiment. During specific particle interactions, the sphere was filled with heavy water, which emitted flashes of light, which were detected and transformed into electronic signals by an array of 9,456 photomultiplier tubes.
Kevin Lesko, a Berkeley Lab physicist who is currently a spokesperson for the LUX-ZEPLIN dark matter experiment in South Dakota, led a team of Berkeley Lab engineers and nuclear scientists who helped build and construct SNO beginning in 1989. To achieve proper coverage by the PMT array, the Berkeley Lab team designed a collection of 751 panels in five different forms that ringed the sphere. The components were designed to be portable so that they could be transported to the underground site in the elevators. Berkeley Lab was also a key contributor to the physics study of SNO’s data.
Kamioka Liquid-scintillator Antineutrino Detector (KamLAND) is a Japanese antineutrino detector
While SNO was focused on solar neutrinos, KamLAND was created to measure neutrinos produced by nuclear reactors. It was the first experiment to prove that the neutrino flavor transformation observed by SNO was caused by a quantum mechanical process known as neutrino oscillation. It also conducted the first research of “geoneutrinos,” or neutrinos created naturally in the Earth’s interior by radioactive element decay, and established limits on a neutrino mixing angle – mixing angles are related to neutrino oscillation rates.
KamLAND’s detector, like SNO’s, was filled with fluid that causes light flashes during particle interactions, and the experiment also included an array of photomultiplier tubes to collect and convert those flashes. Scientists from Berkeley Lab outfitted KamLAND with circuits that transformed analog to digital signals. Berkeley Lab scientists created the technique while working on the IceCube neutrino experiment at the South Pole. Stuart Freedman, a late physicist who died in November 2012, was the driving force behind the United States’ and Berkeley Lab’s participation in KamLAND.
South Pole’s IceCube Neutrino Observatory
The IceCube Neutrino Observatory, located near the South Pole, employs ice as its detector medium rather than a liquid-filled detector. When neutrinos collide with oxygen nuclei in ice, muons form, and these and other fast-moving particles produce blue light, which IceCube detects and analyses with its array of buried Digital Optical Modules, or DOMs. The light signals reveal details about the neutrinos that triggered the phenomenon.
The pioneering R&D for these spherical DOMs and accompanying circuitry was led by Berkeley Lab’s Dave Nygren and Stuart Kleinfelder. On a network of cables known as strings, the DOMs were lowered into boreholes in the ice and subsequently encased in ice at a depth of up to 1.55 miles (2.5 kilometers). The original experiment, which was finished in 2010, consisted of 86 strings, each with 60 optical sensors attached to it. Berkeley Lab scientists also took part in AMANDA, a previous high-energy neutrino experiment in the South Pole.
IceCube has discovered the first proof of a source for high-energy cosmic neutrinos, which can travel billions of light years through space without stopping. The IceCube group identified a blazar — a massive galaxy with a fast-spinning black hole at its center – as a likely source of high-energy neutrinos based on IceCube data. IceCube also analyzed the proportion of high-energy neutrinos received by the Earth versus those that pass through it.
Neutrino Experiment at Daya Bay Reactor in China
The Daya Bay Reactor Neutrino Experiment was launched northeast of Hong Kong thanks to a first-of-its-kind equal cooperation agreement between the United States and China, and it didn’t take long for the experiment to see its first success. The Daya Bay experiment claimed that it has measured the third of three neutrino mixing angles for the first time with excellent precision just 55 days after it began collecting data. As additional data has been available in the eight years since the Daya Bay experiment began, the precision of that measurement has substantially improved.
The United States’ participation in the experiment, which is hosted by the Beijing-based Institute of High Energy Physics, has been spearheaded by Berkeley Lab and Brookhaven National Laboratory. The so-called “reactor antineutrino anomaly,” which was discovered by Berkeley Lab researchers, was caused by many tests reporting less antineutrino observations than predicted from around reactor locations across the world. A miscalculation for a certain radioactive isotope in nuclear reactor fuel was revealed to be a likely factor to the abnormality, according to the investigation. Kam-Biu Luk, a physicist at Berkeley Lab, is the U.S. spokesman and primary investigator for the Daya Bay project, for which he has received multiple awards. Dan Dwyer of Berkeley Lab led an early investigation of the reactor antineutrino anomaly.
LBNF (Long-Baseline Neutrino Facility) at DUNE (Deep Underground Neutrino Experiment), Illinois, South Dakota
More than 1,000 scientists from 30 countries are working on the Deep Underground Neutrino Experiment and the associated Long-Baseline Neutrino Facility to build the world’s most intense neutrino beam, as well as nearby and faraway detectors to study the properties of those beamed neutrinos, as well as neutrinos produced by other sources in space such as an exploding star and p.
The neutrino beam will be directed to the Sanford Underground Research Facility (Sanford Lab) in South Dakota, where a four-story, 70,000-ton detector will be installed about a mile underground to intercept the neutrinos produced by the PIP-II particle accelerator at Fermi National Accelerator Laboratory. It will take around 800,000 tons of rock to excavate, which is more than double the weight of the Empire State Building.
The Near Detector, which will be deployed 200 feet below earth at Fermilab, is being headed by a Berkeley Lab team, which also invented the necessary technology for the pixelated readout of a Near Detector component known as the liquid argon temporal projection chamber. Dan Dwyer and Matthaeus Leitner of Berkeley Lab were instrumental in this project. Carl Grace of Berkeley Lab is part of a team working on cold electronics for the project’s Far Detector at the Sanford Lab site, which will function at extremely low temperatures.
KATRIN-Karlsruhe Experiment with Tritium Neutrinos in Germany
The KArlsruhe TRItium Neutrino (KATRIN) experiment, which is now underway at the Tritium Laboratory Karlsruhe on the KIT Campus North location, will look into the most important open question in neutrino physics:
What is the neutrino’s absolute mass scale?
Neutrinos are, without a doubt, the most fascinating type of elementary particle. The “ghost particle of the Universe” is a key to many outstanding questions in science, connecting the microcosm of fundamental particles to the Universe’s greatest structures.
Neutrinos are the universe’s lightest particles. Their minuscule mass suggests physics beyond the mainstream model of fundamental particle physics. Neutrinos operate as “cosmic builders” on the biggest scales, influencing the development and distribution of galaxies and so contributing to the shaping of observable structures in the Universe.
Previous tests in Mainz and Troitsk were able to set a 2.3 eV/c2 upper limit on the mass of electron anti-neutrinos. KATRIN will either improve this limit by one order of magnitude to 0.2 eV/c2 (90 percent CL) using the same measurement approach, or discover the true mass if it is greater than 0.35 eV/c2. This will necessitate a two-order-of-magnitude improvement in crucial experimental parameters.
The international KATRIN Collaboration, which includes more than 150 scientists, engineers, technicians, and students from 12 institutions in Germany, the United Kingdom, the Russian Federation, the Czech Republic, and the United States, brings together world-class expertise in tritium-decay in a key experiment in the field of astroparticle physics.
LEGEND: The Neutrino’s Majorana Nature in Germany
Is it true that neutrinos have their own antiparticles? Scientists will be able to learn more about this neutrino property, also known as “Majorana nature,” thanks to the upcoming LEGEND experiment. As a follow-up to the preceding GERDA and Majorana trials, LEGEND was established.
According to current knowledge, there is an antiparticle with the opposite electric charge for every charged spin-1/2 particle: anti-quarks and anti-leptons (positron, anti-muon, and anti-tau). Due to the electrical neutrality of the corresponding neutrinos, they may deviate from this scheme and be their own antiparticle. If this is proven empirically, it could open up new avenues for improving our knowledge of the universe’s physics.
So, how can scientists figure out if neutrinos are antiparticles of themselves?
They can look for neutrinoless double beta decay, in which two neutrons are transformed into two protons and two electrons, which only happens if this is the case. Two neutrinos are released in conventional double beta decay. These, on the other hand, are exchanged within the nucleus in neutrinoless decay. However, this can only happen if
- Neutrinos and antineutrinos are the same thing
- and their mass is the same
More than 30 research institutions from approximately ten countries are involved in LEGEND. The Max Planck Institute for Physics’ group is focusing on improving germanium detectors (GeDET). MINIDEX, which researches neutrons as a potential source of disturbances, and PEN, which is designing and implementing new forms of optically active components composed of plastic, which are already being placed in LEGEND 200, are two further subprojects in which the group is working.
Experiment on Accelerator Neutrino Neutron Interaction SciBooNE Hall, Illinois, United States
The Accelerator Neutrino Neutron Interaction Experiment (ANNIE) is a 26-ton water-based neutrino detector on the Booster Neutrino Beam (BNB) at Fermilab with great goals. The project’s purpose is to create a next-generation neutrino detector employing improved photosensors and novel experimental methodologies, all while learning more about how neutrinos interact with matter. Studies of final-state neutron multiplicity from neutrino-nucleus interactions will help us better understand the complicated, many-body dynamics of neutrino-nucleus interactions and, as a result, will assist to decrease dominating systematics on future long-baseline neutrino oscillation measurements.
Identifying and counting final state neutrons also gives future neutrino investigations a viable experimental handle for signal-background separation. The first application of Large Area Picosecond Photodetectors (LAPPDs), which will allow detailed timing-based reconstruction of the primary neutrino interaction, and the first use of gadolinium-enhanced water on a high-energy neutrino beam to efficiently count final-state neutrons, make this measurement possible. The first phase of ANNIE, which was designed to give a measurement of crucial neutron backgrounds, was completed successfully in 2017. The Phase II detector for the experiment’s full physics program was installed in July 2019 and is currently being commissioned. In December 2019, the partnership plans to begin collecting neutrino beam data.
ANTARES ANTARES ANTARES ANTARE (telescope) Mediterranean Sea, France
The neutrino detector ANTARES is located 2.5 kilometers beneath the Mediterranean Sea off the coast of Toulon, France. It’s intended to be utilized as a directional neutrino telescope, locating and observing neutrino flux from cosmic origins in the direction of the Earth’s Southern Hemisphere, as a complement to the IceCube neutrino detector at the South Pole, which detects neutrinos from both hemispheres. The term is also the name of the bright star Antares. It derives from the Astronomy with a Neutrino Telescope and Abyss environmental RESearch project. The experiment is a CERN-approved experiment (RE6). The Greek NESTOR telescope and the Italian NEMO telescope, both in the early phases of development, are two more neutrino telescopes planned for usage in the area.
The IceCube Neutrino Observatory in Antarctica is supplemented by the ANTARES project. Although ANTARES only points to the Southern Hemisphere, the two missions’ detection methodologies are extremely similar. ANTARES is particularly sensitive to neutrinos with energy below 100 TeV in the southern sky, an area that includes numerous galactic sources, due to its position in the Mediterranean Sea. ANTARES will detect neutrinos with high energies, especially between 1010 and 1014 electronvolts (10 GeV – 100 TeV). It may be able to provide a map of the neutrino flux from cosmic origins in the Southern Hemisphere after several years of operation. The detection of astrophysical point sources of neutrinos, possibly in conjunction with observations in other bands, would be of special interest (such as gamma rays sources observed by the HESS telescope in Namibia, which has a common field of view with ANTARES).
Apart from astro-particle physics, the ANTARES telescope may also be used to investigate some fundamental problems in particle physics, such as the search for dark matter in the form of neutralino annihilation in the sun (normal solar neutrinos are outside ANTARES’ energy range) or the galactic center. Its expected sensitivity is complementary to direct dark matter searches undertaken by other experiments such as DAMA, CDMS, and at the LHC, due to the very diverse approaches used. Supersymmetry would also be confirmed by the detection of neutralino signals, but this is not thought to be particularly likely at the ANTARES sensitivity level. Nuclearites and magnetic monopoles are two further “abnormal” occurrences that could be observed by ANTARES.
ARIANNA Experiment Ross Ice Shelf, Antarctica
A proposed detector for ultra-high energy astrophysical neutrinos is the ARIANNA Experiment Antarctic Ross Ice-Shelf Antenna Neutrino Array (ARIANNA). It will detect coherent radio Cherenkov emissions from neutrino particle showers with energy greater than 1017 eV. ARIANNA will be erected on the Ross Ice Shelf, which is located just off the coast of Antarctica, and will eventually cover an area of around 900 km2. The ice-water contact beneath the shelf reflects radio waves, strengthening ARIANNA’s sensitivity to horizontally incident neutrinos while also increasing its sensitivity to downward traveling neutrinos. Each ARIANNA detector station will have 4-8 antennas that will look for brief pulses of radio emission from neutrino interactions ranging from 50 MHz to 1 GHz.
A prototype array of seven stations has been erected and was collecting data as of 2016. An first search for neutrinos yielded no results, therefore an upper limit was established.
Borexino Gran Sasso, Italy
Borexino is a particle physics experiment that studies solar neutrinos with low energy (sub-MeV). The detector is a liquid scintillator calorimeter that is the world’s most radio-pure. It is housed in a stainless steel sphere that houses the photomultiplier tubes (PMTs) employed as signal detectors and is covered by a water tank to protect it from external radiation and tag incoming cosmic muons that make it beyond the mountain’s overburden.
The experiment’s main goal is to take exact measurements of individual neutrino fluxes from the Sun and compare them to predictions from standard solar models. This will allow scientists to test and better understand the Sun’s functioning (e.g., nuclear fusion processes at the Sun’s core, solar composition, opacity, matter distribution, and so on), as well as determine features of neutrino oscillations, such as the MSW effect. The experiment’s specific targets are to detect solar neutrinos such as beryllium-7, boron-8, pp, pep, and CNO, as well as anti-neutrinos from the Earth and nuclear power plants. With a specific potential to detect the elastic scattering of neutrinos onto protons due to neutral current interactions, the project may also be able to detect neutrinos from supernovae within our galaxy. Borexino is a Supernova Early Warning System member. Rare processes and potentially unknown particles are also being investigated.
Borexino is an Italian diminutive of BOREX (Boron solar neutrino Experiment), which was abandoned after the original 1 kT-fiducial experimental proposal with a different scintillator (TMB) was shelved due to a shift in physics goals as well as financial restrictions.
The experiment is being carried out at the Laboratori Nazionali del Gran Sasso near L’Aquila, Italy, and is backed by an international partnership with scientists from Italy, the United States, Germany, France, Poland, Russia, and Ukraine.  The experiment is supported by a number of governmental bodies, the most important of which being INFN (Italian National Institute for Nuclear Physics) and NSF (National Science Foundation) (National Science Foundation, USA). Borexino celebrated ten years of uninterrupted operation in May 2017 from the commencement of its data-gathering phase in 2007.
The SOX experiment used a neutrino generator based on radioactive cerium-144 put directly beneath the water tank of the Borexino detector to investigate the possibility of sterile neutrinos or other anomalous effects in neutrino oscillations at short ranges. Due to insurmountable technical issues in the manufacture of the antineutrino source, this project was canceled in early 2018.
Deep Underground Neutrino Experiment Winfield Township, Lead, US
The Deep Underground Neutrino Experiment (DUNE) is a neutrino experiment that is currently in the works, with a near detector at Fermilab and a distant detector at the Sanford Underground Research Facility, both of which will monitor neutrinos created at Fermilab. It will fire a powerful beam of trillions of neutrinos over a distance of 1,300 kilometers (810 miles) from a manufacturing plant at Fermilab in Illinois to a 70-kiloton volume of liquid argon deep down at the Sanford Lab in South Dakota. The neutrinos will travel in a straight line through the Earth, reaching a depth of around 30 kilometers (19 miles) towards the midpoint (the far detector will be 1.5 kilometers (4,850 feet) beneath the surface). To build the caverns for the remote detectors, some 800,000 tons of rock will be dug. The project involves around 1,000 contributors.
The Long Baseline Neutrino Experiment (LBNE) was originally conceived as a US-only study; however, between 2012 and 2014, a descope with a near-surface detector was investigated as a cost-cutting measure. However, in a 2014 report, the Particle Physics Project Prioritization Panel (P5) concluded that LBNE’s research activity “should be reformulated under the auspices of a new international collaboration, as an internationally coordinated and internationally funded program, with Fermilab as host,” reverting to a deep-underground detector. On January 30, 2015, the LBNE partnership was officially terminated, just days after the P5-recommended new collaboration was founded on January 22, 2015. Deep Underground Neutrino Experiment is the name chosen by the new collaboration (DUNE)
Hyper-Kamiokande Tokai and Kamioka, Japan
Hyper-Kamiokande is a neutrino observatory being built at Kamioka, Japan, on the site of the Kamioka Observatory.
As a follow-up to Super-Kamiokande, the project began in 2010. It was named one of the Japanese government’s top 28 priority projects. This program involves thirteen countries from three continents.
Construction is set to begin in April 2020 after receiving final approval on December 13, 2019.
Data collection is expected to commence in 2027.
Hyper-Kamiokande will have a tank that holds a billion litres of ultrapure water (UPW), which is 20 times larger than Super-tank. Kamiokande’s A corresponding rise in the number of sensors will accompany this enhanced capacity. Hyper-tank Kamiokande’s will be a double cylinder 2 250 meters long, constantly around 40 meters, and buried 650 meters deep to decrease cosmic radiation interference.
The hunt for proton decays will be one of the scientific goals. Super-Kamiokande set a lower bound on the proton’s half life of around 1034, which is adequate to rule out some Grand Unified Theories (GUTs) like SU(5); Hyper-Kamiokande will set a lower bound of around 1035, allowing for the testing of other GUT candidates.
Experiment ICARUS Gran Sasso, Italy
ICARUS (Imaging Cosmic And Rare Underground Signals) is a neutrino-related physics experiment. It was housed at the Gran Sasso National Laboratories (LNGS). It was renovated at CERN after completion of its operations there, and it was re-used in the same Fermilab neutrino beam as the MiniBooNE, MicroBooNE, and SBND experiments. The ICARUS detector was then dismantled and reassembled at Fermilab for shipping. Fermilab scientists began cooling ICARUS and filling it with 760 tons of liquid argon in February 2020. The first measurements with the renovated ICARUS are expected later in 2020.
Carlo Rubbia presented a novel sort of neutrino detector in 1977, which sparked the ICARUS program. These are known as Liquid Argon Time Projection Chambers (LAr-TPC), and they are designed to combine the benefits of bubble chambers and electronic detectors, therefore improving upon prior detectors. Detectors of this size and capability were proposed as part of the ICARUS program. The ICARUS T600 detector at Gran Sasso, packed with 760 tons of liquid argon, began operation in 2010 after first runs in Pavia in 2001. Neutrinos from astronomical or solar sources, as well as the CERN Neutrinos to Gran Sasso (CNGS) beam produced 730 kilometers away by CERN’s Super Proton Synchrotron, have been detected through the reaction in order to research neutrino oscillations and numerous fundamental themes in current physics.
The OPERA experiment also studies CNGS neutrinos, hence those experiments are also known as CNGS1 (OPERA) and CNGS2 (ICARUS).
When the OPERA group stated in September and November 2011 that they had measured superluminal neutrinos, the CNGS measurements became even more noteworthy (see faster-than-light neutrino anomaly). The ICARUS project issued a study shortly after, arguing that the energy distribution of neutrinos is incompatible with superluminal particles. Cohen and Sheldon Lee Glashow proposed a theory that led to this finding. They presented a direct neutrino velocity measurement based on seven neutrinos events in March of 2012. The finding agrees with the speed of light, implying special relativity, and contradicts the OPERA result.  Another neutrino velocity measurement based on 25 neutrino events was published in August 2012, with improved precision and statistics, and was found to be in accord with the speed of light once more (see neutrino velocity measurements).
In July 2017, the ICARUS detector was relocated to Fermilab for a new neutrino investigation.
ICARUS is expected to begin operations later in 2020, in February.
Jiangmen Neutrino Observatory is an underground neutrino observatory in Jiangmen, China
The Jiangmen Underground Neutrino Observatory (JUNO) is a medium-baseline reactor neutrino experiment now being built in Kaiping, Jiangmen, China. Its goal is to figure out the neutrino mass hierarchy and measure the Pontecorvo–Maki–Nakagawa–Sakata matrix elements with precision. It will build on the results of many prior studies with mixing parameters. Construction on the project began on January 10, 2015, after the agreement was formed in July 2014. The plan is to start collecting data in 2021. The Chinese Academy of Sciences provides funding, although the collaboration is transnational.
It was initially planned for the same location as the Daya Bay Reactor Neutrino Experiment, however building of a third nuclear reactor (the planned Lufeng nuclear power station) in the vicinity would disrupt the experiment, which relies on maintaining a set distance from nearby nuclear reactors. Instead, it was relocated 53 kilometers from both the Yangjiang and Taishan nuclear power plants.
NEVOD Moscow, Russia
NEVOD is a neutrino detector and cosmic ray experiment that aims to detect Cherenkov radiation produced by water-charged particle interactions (mostly muons). It’s the first time such observations have been attempted at the Earth’s surface, and it’s because of this that the experiment can also explore cosmic rays. The Moscow Engineering Physics Institute is home to NEVOD (MEPhI).
The experimental complex built around the original water Cherenkov detector for the study of cosmic rays is known as the NEVOD experimental complex; as of 2018, the experimental complex consists of the Cherenkov water detector (the eponymous NEVOD detector), a coordinate-tracking detector DECOR, an array of scintillation detectors forming the calibration telescopes system CTS, and the PRISMA array. Three more cosmic ray detectors have been added to the experimental complex as of 2018: NEVOD-EAS (for determining cosmic ray air shower characteristics), URAN (neutron detector), and TREK (drift chamber detector). Some of the new detectors are already in use (in 2018).
URAGAN, a muon hodoscope that was operational in 2016 and preceding years, was also housed in the experimental facility. URAGAN’s current status (as of 2019) is unknown.
According to its creators, NEVOD comprises of a 9 m x 9 m x 26 m water reservoir into which a spatial lattice of quasi-spherical detector modules (QSMs) is inserted to record Cherenkov radiation from any direction. The reservoir’s size allow for the placement of up to 241 QSMs.
The quasi-spherical modules are made up of an array of six photomultiplier tubes arrayed along the device’s principal axes, rather than being spherical. The PMTs are arranged in such a way that their reaction is solely based on the intensity of the incident radiation, not on its angle of incidence (beyond the device’s visible angles), making the entire detector “quasi-spherical.”
NEVOD began operations in 1994, was featured in a journal in 1995, and has since been utilized for both primary research and instruction. Many detectors have been added to the initial Cherenkov detector since the inception of the NEVOD experiment, resulting in the NEVOD experimental complex. The Cherenkov detector has also been improved a number of times. In 2015-2016, there was talk of upgrading the experimental complex.