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McDonald of Canada received the Nobel Prize for Physics for their landmark finding, theoretical and experimental, that neutrinos can change flavors. The Aeolus robot can clean your house, pick up after you and keep an eye on things while you're away. Kohler's new bathtub supports voice commands for water temperature and fill level, or tweaking via the company's new Konnect app. Other research is focused on measurement of unknown properties of neutrinos, especially their masses and CP violation , as they cannot be predicted with existing theories. The views expressed in the contents above are those of our users and do not necessarily reflect the views of MailOnline.
Samsung has not announced pricing, availability or really any details about how this technology could reach the market. Robots are everywhere at CES this year, and Ubtech's biped contains multitudes. The Walker is prepared to tackle your security needs, patrolling your home's perimeter, detecting motion and recording incidents with its integrated camera.
And when it's quitting time, it can dance and play games. Pretty good for a robot with no arms. The Misty I, on the other hand, is but a wee baby robot -- though one born into an esteemed family that's laser-focused on its future.
Smacircle, based in Shenzhen, China, claims it's built the world's most compact and lightweight foldable eBike. Weighing in at roughly 15 pounds 6. If you need a little help getting around, this is one bad-ass personal electric vehicle.
The Whill Model Ci has a max speed of 5 mph and a battery range of up to 10 miles; the integrated lithium-ion battery takes between 4 and 5 hours to charge.
Though it's not an all-terrain vehicle, it can handle inclines and a variety of surfaces -- and the accompanying app allows family members to check battery level and location remotely. Backers of that campaign will soon receive the Fenix AR -- a helmet with a rear-view camera that displays a degree view on a transparent display. The Bluetooth headphone that could finally get audiophiles to cut the cord. This EEG headset from Belgian research center Imec can assess your emotional state based on signals from the front of your brain.
There are therapeutic applications, sure, but it also has the potential to improve your memory when you're learning, match music to your mood or even adjust your emotions by changing your music.
Rather than overwhelm you with a flood of features you might not need, Whirlpool has shown some restraint with its smart fridge. The screen will tell you how long to cook your particular cut and ask if you want to set a timer. Whirlpool will suspend cooling to save energy and shut off the door alarm.
This prototype phone shown by Chinese phonemaker Vivo has no official name, price or sale date. But its virtual home button, which appears only when you need it and then gets out of the way, may be a harbinger of things to come. It's a killer feature that was rumored for both the iPhone X and Samsung Galaxy S8 -- neither of which had it.
We're clinging to the hope that it finds its way onto the forthcoming Samsung Galaxy S9. Kino-mo's Hypervsn Wall is getting a lot of attention here in Las Vegas. Made up of multiple propeller-looking modules adorned with programmable LEDs, the Wall creates holographic images up to 3 meters in size. Toto's marble-covered bathtub has lots of integrated tech -- but what separates it from the rest is its ability to simulate the feeling of floating in space.
A series of integrated jets lift your feet off the floor of the tub and the surrounding LED lights add the perfect interstellar ambiance. Razor, renowned maker of scooters, has developed yet another way to test the patience of parents. The company's new Turbo Jetts motorized heel wheels go up to 10 mph. The removable battery, which will give you 2 to 4 hours of peace while it charges, delivers about 30 minutes of motorized wheel time.
The device can be adjusted to fit both kids size 12 and up and, when the inevitable "time out" is served, adults up to adult size Sony's groundbreaking robot dog is back with some new tricks. Equipped with an artificial intelligence boost for , Aibo can now recognize and respond to multiple family members. And with its wireless cloud connectivity, it can store and process everything that it learns from living with you. The all-electric FF91 Future, shown here in the Stealth Combat finish, looks seriously cool, is autonomous-ready and, according to Faraday, goes from 0 to 60 in 2.
Though there's no word on price yet, Faraday says the FF91 will hit customer driveways later this year. Sure, it's a prototype, but it works -- literally. The Aeolus robot can clean your house, pick up after you and keep an eye on things while you're away. Merge has given it six-degree-of-freedom 6DoF tracking, which phone-connected rival headsets have a hard time with. You can walk around with it, duck and aim quickly.
Fun, and surely a sign that there are more AR toys to come. Say goodbye to cable. It's available for preorder now. Intel CEO Brian Krzanich used his keynote to show off the Volocopter, an autonomous passenger drone, which he called "essentially a flying car. It may look like your average laptop, but there's no Intel inside. Instead, there's a slot where the touchpad would normally be for you to dock Razer's own Android-powered phone.
Now you've got a Frankenstein's monster with the phone as the brain -- serving up its processor, operating system and apps -- in the body of a Blade Stealth laptop. Batteries aren't included or even necessary here. That's because Razer's new wireless gaming mouse pulls its power directly from its mousepad.
So the new Mamba is a few ounces lighter than its predecessors, but it still has Chroma accent lights that you can control from your PC. Have you ever wanted a gigantic Jumbotron for your own home? The new model, called The Wall, measures a mind-blowing inches. HTC is upping its virtual reality game. The new Vive Pro will offer enhanced resolution, integrated headphones and, perhaps most important, a new wireless adaptor that will let you finally roam virtual worlds untethered. Nanoleaf has unveiled a new square-shaped variation of its light panels.
Now you can turn the panels on and off, dim them up and down, or change their color just by tapping on them. Yes, of course, there's also a music sync microphone and motion sensor capable of lighting the panels up whenever you walk by.
The e-Palette is Toyota's new, modular transportation platform that looks inspired by both shipping container and toaster. It comes in three sizes ranging from 4 meters about 13 feet to approximately 7 meters around 23 feet and is designed to be flexible and reconfigurable to accommodate the needs of Toyota's partners on the project, which include Amazon, Pizza Hut, Uber and others. Hauling your luggage around an airport is very We are now in , however, and this year we finally get a chance to buy a hands-free, autonomous carry-on suitcase that will follow you anywhere at a max speed of 7 mph 11 kph.
Maker ForwardX plans to launch the luggage sometime later this year, but hasn't announced pricing. The projector itself has built-in speakers and Hisense includes a wireless subwoofer, too. Sony's new ultra-short-throw projector looks like a stylish credenza, with an artificial marble top and half-mirror aluminum frame and wooden shelf.
Built into the top, however, is a projector that can create a inch image with 4K resolution. Sony has also integrated organic glass speakers, a subwoofer and three midrange speakers.
The monstrous inch XF sticks with its predecessor's full-array local dimming LED backlight and adds Dolby Vision high dynamic range compatibility. The makeup master has developed a battery-free wearable that measures UV exposure.
At only 2mm thick and 9mm in diameter, the tiny electronic sensor can be worn on a fingernail or pair of sunglasses and, via an app, will give you warnings about sun exposure. It's available exclusively through dermatologists in with a global launch planned for Imagine it at the foot of your four-poster bed or the end of your luxury bath. We can dream that this futuristic boob tube will hit the market soon, but LG hasn't announced pricing or availability, let alone an explanation of how the thing actually works.
Sony's highest-end Xperia features a wide angle camera that can shoot degree photos at 8 megapixels as well as megapixel standard-angle photos. Plus, a fingerprint sensor on the back.
The phone will sell in select countries starting in late January, and pricing has not yet been announced. If you're looking for the perfect mobile accessory for your retro '90s outfit, the Gemini clamshell is for you. Pure throwback on the outside, but all business on the inside with a core processor, 64GB of storage and 4G, Wi-Fi and Bluetooth connectivity.
It's not yet in stores, but you can preorder via Indiegogo. Brush teeth, kill monsters, prevent cavities. Wait, go back one. And this inch behemoth will blow your eyes out of your head with its 7,x4,pixel resolution -- four times that of your now-middling 4K set and 16 times more than a pitiable standard full-HD TV. You'll still have to wait for actual 8K things to watch, however. Equipped with a kW e-motor, Hyundai estimates the Nexo's prototype fuel cell powertrain, bolstered by three bar hydrogen tanks and a 1.
Plus, the only emission it leaves behind is water vapor. We drove one here to Vegas -- hit the Read More link to find out more.
Google Glass is gone. Into the void steps Amazon's Alexa virtual assistant, hitching a ride aboard the Vuzix Blade smart glasses. Vuzix has embedded a camera, microphone and side-mounted touchpad in this chunky but pretty normal-looking pair of sunglasses, which takes phone calls and puts Alexa's giant brain between your ears.
Every CES there's a competition over who has the skinniest device. This year, thinnest laptop award goes to the Acer Swift 7 -- at 8.
Garmin could leave Apple in the dust with this one. The Forerunner music watch, with storage for songs, also supports GPS, Garmin Pay and has physical buttons instead of a touchscreen -- which may be preferable for those on the move.
Availability is not yet announced. All of the upsides of a high-end gaming rig without the cost or technical requirements of actually owning one. Available in California starting Feb.
That's not the only subscription service for gamers, though. Nvidia had its GeForce now service on show, which, similar to the Blade Shadow service, lets you play demanding games on any hardware, all thanks to the magic of the internet.
Pricing and official launch details are not yet known. Equipped with a mobile app, an emphasis on ease of use and a reasonable price, the da Vinci Nano 3D could be the portable, single-color 3D printer affordable enough for the home and classroom.
This picture isn't of one super-long screen, it's three screens next to each other. The bezels are hidden, though, by Asus' new antibezel kit. It uses lenses to refract the content on the screen edges at a degree angle -- essentially using a sort of stealth technology to hide them. Samsung's newest smart refrigerator recommends recipes based on your family's food preferences, allergies and, thanks to the integrated cameras, the ingredients you have on hand.
And the new Deals app saves sale-priced groceries to your shopping list. The Spectre x lives a double life as a tablet and high-performance laptop. Coming to Best Buy and HP. Does your toilet feel excluded from your smart home setup? Kohler's new top-of-the-line model delivers hands-free flushing, bidet cleansing, feet warming, air drying, odor control, music, a night light and automatic seat temperature management.
A practical method for investigating neutrino oscillations was first suggested by Bruno Pontecorvo in using an analogy with kaon oscillations ; over the subsequent 10 years he developed the mathematical formalism and the modern formulation of vacuum oscillations. In Stanislav Mikheyev and Alexei Smirnov expanding on work by Lincoln Wolfenstein noted that flavor oscillations can be modified when neutrinos propagate through matter.
This so-called Mikheyev—Smirnov—Wolfenstein effect MSW effect is important to understand because many neutrinos emitted by fusion in the Sun pass through the dense matter in the solar core where essentially all solar fusion takes place on their way to detectors on Earth. Starting in , experiments began to show that solar and atmospheric neutrinos change flavors see Super-Kamiokande and Sudbury Neutrino Observatory. This resolved the solar neutrino problem: Although individual experiments, such as the set of solar neutrino experiments, are consistent with non-oscillatory mechanisms of neutrino flavor conversion, taken altogether, neutrino experiments imply the existence of neutrino oscillations.
The KamLAND experiment has indeed identified oscillations as the neutrino flavor conversion mechanism involved in the solar electron neutrinos. Similarly MINOS confirms the oscillation of atmospheric neutrinos and gives a better determination of the mass squared splitting. McDonald of Canada received the Nobel Prize for Physics for their landmark finding, theoretical and experimental, that neutrinos can change flavors. Both conducted pioneering work on solar neutrino detection, and Koshiba's work also resulted in the first real-time observation of neutrinos from the SN A supernova in the nearby Large Magellanic Cloud.
These efforts marked the beginning of neutrino astronomy. Also being leptons, neutrinos have been observed to interact through only the weak force , although it is assumed that they also interact gravitationally. Although neutrinos were long believed to be massless, it is now known that there are also three discrete neutrino masses, but they don't correspond uniquely to the three flavors.
Although only differences of squares of the three mass values are known as of ,  experiments have shown that these masses are tiny in magnitude. From cosmological measurements, it has been calculated that the sum of the three neutrino masses must be less than one millionth that of the electron. More formally, neutrino flavor eigenstates are not the same as the neutrino mass eigenstates simply labelled 1, 2, 3. As of , it is not known which of these three is the heaviest.
Several major experimental efforts are underway to help establish which is correct. A neutrino created in a specific flavor eigenstate is in an associated specific quantum superposition of all three mass eigenstates. This is possible because the three masses differ so little that they cannot be experimentally distinguished within any practical flight path, due to the uncertainty principle.
The proportion of each mass state in the produced pure flavor state has been found to depend strongly on that flavor. The relationship between flavor and mass eigenstates is encoded in the PMNS matrix. Experiments have established values for the elements of this matrix. The existence of a neutrino mass allows the possibility of a tiny neutrino magnetic moment , in which case neutrinos could interact electromagnetically as well; no such interaction has been discovered.
Neutrinos oscillate between different flavors in flight. For example, an electron neutrino produced in a beta decay reaction may interact in a distant detector as a muon or tau neutrino, as defined by the flavor of the charged lepton produced in the detector.
This oscillation occurs because the three mass state components of the produced flavor travel at slightly different speeds, so that their quantum mechanical wave packets develop relative phase shifts that change how they combine to produce a varying superposition of three flavors. Each flavor component thereby oscillates sinusoidally as the neutrino travels, with the flavors varying in relative strengths. The relative flavor proportions when the neutrino interacts represent the relative probabilities for that flavor of interaction to produce the corresponding flavor of charged lepton.
There are other possibilities in which neutrino could oscillate even if they were massless. If Lorentz symmetry were not an exact symmetry, neutrinos could experience Lorentz-violating oscillations.
Neutrinos traveling through matter, in general, undergo a process analogous to light traveling through a transparent material. This process is not directly observable because it does not produce ionizing radiation , but gives rise to the MSW effect.
Only a small fraction of the neutrino's energy is transferred to the material. For each neutrino, there also exists a corresponding antiparticle , called an antineutrino , which also has no electric charge and half-integer spin.
They are distinguished from the neutrinos by having opposite signs of lepton number and opposite chirality. As of , no evidence has been found for any other difference. In all observations so far of leptonic processes despite extensive and continuing searches for exceptions , there is no overall change in lepton number; for example, if total lepton number is zero in the initial state, electron neutrinos appear in the final state together with only positrons anti-electrons or electron-antineutrinos, and electron antineutrinos with electrons or electron neutrinos.
Antineutrinos are produced in nuclear beta decay together with a beta particle , in which, e. All antineutrinos observed thus far possess right-handed helicity i. Nevertheless, as neutrinos have mass, their helicity is frame -dependent, so it is the related frame-independent property of chirality that is relevant here. Antineutrinos were first detected as a result of their interaction with protons in a large tank of water. This was installed next to a nuclear reactor as a controllable source of the antineutrinos See: Researchers around the world have begun to investigate the possibility of using antineutrinos for reactor monitoring in the context of preventing the proliferation of nuclear weapons.
Because antineutrinos and neutrinos are neutral particles, it is possible that they are the same particle. Particles that have this property are known as Majorana particles , after the Italian physicist Ettore Majorana who first proposed the concept. For the case of neutrinos this theory has gained popularity as it can be used, in combination with the seesaw mechanism , to explain why neutrino masses are so small compared to those of the other elementary particles, such as electrons or quarks.
Majorana neutrinos have the property that the neutrino and antineutrino could be distinguished only by chirality ; what experiments observe as a difference between the neutrino and antineutrino could simply be due to one particle with two possible chiralities. It is not yet known whether neutrinos are Majorana or Dirac particles; it is possible to test this property experimentally.
For example, if neutrinos are indeed Majorana particles, then lepton-number violating processes such as neutrinoless double beta decay would be allowed, while they would not if neutrinos are Dirac particles. Several experiments have been and are being conducted to search for this process, e.
Neutrinos can interact with a nucleus, changing it to another nucleus. This process is used in radiochemical neutrino detectors. In this case, the energy levels and spin states within the target nucleus have to be taken into account to estimate the probability for an interaction.
In general the interaction probability increases with the number of neutrons and protons within a nucleus. It is very hard to uniquely identify neutrino interactions among the natural background of radioactivity. For this reason, in early experiments a special reaction channel was chosen to facilitate the identification: A hydrogen nucleus is a single proton, so simultaneous nuclear interactions, which would occur within a heavier nucleus, don't need to be considered for the detection experiment.
Within a cubic metre of water placed right outside a nuclear reactor, only relatively few such interactions can be recorded, but the setup is now used for measuring the reactor's plutonium production rate. Very much like neutrons do in nuclear reactors , neutrinos can induce fission reactions within heavy nuclei.
The process affects the abundance of isotopes seen in the universe. Observations of the cosmic microwave background suggest that neutrinos do not interact with themselves.
There are three known types flavors of neutrinos: The current best measurement of the number of neutrino types comes from observing the decay of the Z boson. Measurements of the Z lifetime have shown that the number of light neutrino flavors that couple to the Z is 3. Proof that there are only three kinds of neutrinos remains an elusive goal of particle physics.
There are several active research areas involving the neutrino. Some are concerned with testing predictions of neutrino behavior. Other research is focused on measurement of unknown properties of neutrinos, especially their masses and CP violation , as they cannot be predicted with existing theories.
International scientific collaborations install large neutrino detectors near nuclear reactors or in neutrino beams from particle accelerators to better constrain the neutrino masses and the values for the magnitude and rates of oscillations between neutrino flavors. These experiments are thereby searching for the existence of CP violation in the neutrino sector; that is, whether or not the laws of physics treat neutrinos and antineutrinos differently.
The KATRIN experiment in Germany has begun to acquire data in June  to determine the value of the mass of the electron neutrino, with other approaches to this problem in the planning stages. Despite their tiny masses, neutrinos are so numerous that their gravitational force can influence other matter in the universe.
The three known neutrino flavors are the only established elementary particle candidates for dark matter , specifically hot dark matter , although that possibility appears to be largely ruled out by observations of the cosmic microwave background.
If heavier sterile neutrinos exist, they might serve as warm dark matter , which still seems plausible. Other efforts search for evidence of a sterile neutrino — a fourth neutrino flavor that does not interact with matter like the three known neutrino flavors. If their mass is greater than half the Z-boson's mass, they would not be a decay product. Therefore, heavy sterile neutrinos would have a mass of at least The existence of such particles is in fact hinted by experimental data from the LSND experiment.
On the other hand, the currently running MiniBooNE experiment suggested that sterile neutrinos are not required to explain the experimental data,  although the latest research into this area is on-going and anomalies in the MiniBooNE data may allow for exotic neutrino types, including sterile neutrinos.
According to an analysis published in , data from the Wilkinson Microwave Anisotropy Probe of the cosmic background radiation is compatible with either three or four types of neutrinos.
If this were discovered the two could no longer be mutual antiparticles, and each of the resulting six distinct neutrinos would have no distinct antiparticle partner. Before neutrinos were found to oscillate, they were generally assumed to be massless, propagating at the speed of light.
According to the theory of special relativity , the question of neutrino velocity is closely related to their mass: Due to their tiny mass, the predicted speed is extremely close to the speed of light in all experiments, and current detectors are not sensitive to the expected difference. Also some Lorentz-violating variants of quantum gravity might allow faster-than-light neutrinos.
In the early s, first measurements of neutrino speed were done using pulsed pion beams produced by pulsed proton beams hitting a target. The pions decayed producing neutrinos, and the neutrino interactions observed within a time window in a detector at a distance were consistent with the speed of light.
The central value of 1. A similar observation was made, on a much larger scale, with supernova A SN A. So far, all measurements of neutrino speed have been consistent with the speed of light. The results showed the same faster-than-light speed. An independent recreation of the experiment in the same laboratory by ICARUS found no discernible difference between the speed of a neutrino and the speed of light.
The Standard Model of particle physics assumed that neutrinos are massless. The experimentally established phenomenon of neutrino oscillation, which mixes neutrino flavour states with neutrino mass states analogously to CKM mixing , requires neutrinos to have nonzero masses.
Enhancing the basic framework to accommodate their mass is straightforward by adding a right-handed Lagrangian. The strongest upper limit on the masses of neutrinos comes from cosmology: A much more stringent constraint comes from a careful analysis of cosmological data, such as the cosmic microwave background radiation, galaxy surveys , and the Lyman-alpha forest. McDonald for their experimental discovery of neutrino oscillations, which demonstrates that neutrinos have mass.
In , research results at the Super-Kamiokande neutrino detector determined that neutrinos can oscillate from one flavor to another, which requires that they must have a nonzero mass. This is because neutrino oscillations are sensitive only to the difference in the squares of the masses. A number of efforts are under way to directly determine the absolute neutrino mass scale in laboratory experiments.
On 31 May , OPERA researchers observed the first tau neutrino candidate event in a muon neutrino beam, the first time this transformation in neutrinos had been observed, providing further evidence that they have mass.
If the neutrino is a Majorana particle , the mass may be calculated by finding the half-life of neutrinoless double-beta decay of certain nuclei. Standard Model neutrinos are fundamental point-like particles, without any width or volume. Since the neutrino is an elementary particle it does not have a size in the same sense as everyday objects. The electron neutrino cross section is 3. These scattering cross sections depend on no other properties than the masses of the corresponding charged leptons.
Properties associated with conventional "size" are absent: Experimental results show that nearly all produced and observed neutrinos have left-handed helicities spins antiparallel to momenta , and all antineutrinos have right-handed helicities, within the margin of error. These are the only chiralities included in the Standard Model of particle interactions. It is possible that their counterparts right-handed neutrinos and left-handed antineutrinos simply do not exist. If they do, their properties are substantially different from observable neutrinos and antineutrinos.
It is theorized that they are either very heavy on the order of GUT scale —see Seesaw mechanism , do not participate in weak interaction so-called sterile neutrinos , or both. The existence of nonzero neutrino masses somewhat complicates the situation. Neutrinos are produced in weak interactions as chirality eigenstates. Chirality of a massive particle is not a constant of motion; helicity is, but the chirality operator does not share eigenstates with the helicity operator.
This does not significantly affect the experiments, because neutrinos involved are nearly always ultrarelativistic, and thus mixing amplitudes are vanishingly small. Effectively, they travel so quickly and time passes so slowly in their rest-frames that they do not have enough time to change over any observable path. An unexpected series of experimental results for the rate of decay of heavy highly charged radioactive ions circulating in a storage ring has provoked theoretical activity in an effort to find a convincing explanation.
The rates of weak decay of two radioactive species with half lives of about 40 s and s are found to have a significant oscillatory modulation , with a period of about 7 s.
As the decay process produces an electron neutrino , some of the proposed explanations for the observed oscillation rate invoke neutrino properties. Initial ideas related to flavour oscillation were met with skepticism. Nuclear reactors are the major source of human-generated neutrinos. The antineutrino energy spectrum depends on the degree to which the fuel is burned plutonium fission antineutrinos on average have slightly more energy than those from uranium fission , but in general, the detectable antineutrinos from fission have a peak energy between about 3.
The ND detector has been proposed as a viable safeguard unit. Some particle accelerators have been used to make neutrino beams.
The technique is to collide protons with a fixed target, producing charged pions or kaons. These unstable particles are then magnetically focused into a long tunnel where they decay while in flight.
Because of the relativistic boost of the decaying particle, the neutrinos are produced as a beam rather than isotropically. Efforts to construct an accelerator facility where neutrinos are produced through muon decays are ongoing. Nuclear weapons also produce very large quantities of neutrinos. Fred Reines and Clyde Cowan considered the detection of neutrinos from a bomb prior to their search for reactor neutrinos; a fission reactor was recommended as a better alternative by Los Alamos physics division leader J.
Neutrinos are produced together with the natural background radiation. In particular, the decay chains of U and Th isotopes, as well as 40 K , include beta decays which emit antineutrinos. These so-called geoneutrinos can provide valuable information on the Earth's interior.
Atmospheric neutrinos result from the interaction of cosmic rays with atomic nuclei in the Earth's atmosphere , creating showers of particles, many of which are unstable and produce neutrinos when they decay.
Solar neutrinos originate from the nuclear fusion powering the Sun and other stars. The details of the operation of the Sun are explained by the Standard Solar Model. The Sun sends enormous numbers of neutrinos in all directions. The neutrino signal from the supernova arrived at earth several hours before the arrival of the first electromagnetic radiation, as expected from the evident fact that the latter emerges along with the shock wave.
The exceptionally feeble interaction with normal matter allowed the neutrinos to pass through the churning mass of the exploding star, while the electromagnetic photons were slowed. Because neutrinos interact so little with matter, it is thought that a supernova's neutrino emissions carry information about the innermost regions of the explosion. Much of the visible light comes from the decay of radioactive elements produced by the supernova shock wave, and even light from the explosion itself is scattered by dense and turbulent gases, and thus delayed.
The neutrino burst is expected to reach Earth before any electromagnetic waves, including visible light, gamma rays, or radio waves. The exact time delay of the electromagnetic waves' arrivals depends on the velocity of the shock wave and on the thickness of the outer layer of the star. The Supernova Early Warning System project uses a network of neutrino detectors to monitor the sky for candidate supernova events; the neutrino signal will provide a useful advance warning of a star exploding in the Milky Way.
Although neutrinos pass through the outer gases of a supernova without scattering, they provide information about the deeper supernova core with evidence that here, even neutrinos scatter to a significant extent. In a supernova core the densities are those of a neutron star which is expected to be formed in this type of supernova ,  becoming large enough to influence the duration of the neutrino signal by delaying some neutrinos.
In addition to the detection of neutrinos from individual supernovae, it should also be possible to detect the diffuse supernova neutrino background , which originates from all supernovae in the Universe. The energy of supernova neutrinos ranges from a few to several tens of MeV. The sites where cosmic rays are accelerated are expected to produce neutrinos that are at least one million times more energetic, produced from turbulent gaseous environments left over by supernova explosions: The origin of the cosmic rays was attributed to supernovas by Walter Baade and Fritz Zwicky ; this hypothesis was refined by Vitaly L.
Ginzburg and Sergei I. Syrovatsky who attributed the origin to supernova remnants, and supported their claim by the crucial remark, that the cosmic ray losses of the Milky Way is compensated, if the efficiency of acceleration in supernova remnants is about 10 percent.
Ginzburg and Syrovatskii's hypothesis is supported by the specific mechanism of "shock wave acceleration" happening in supernova remnants, which is consistent with the original theoretical picture drawn by Enrico Fermi , and is receiving support from observational data. The very-high-energy neutrinos are still to be seen, but this branch of neutrino astronomy is just in its infancy.
Indeed, the collisions of cosmic rays are supposed to produce charged pions, whose decay give the neutrinos, and also neutral pions, whose decay give gamma rays: Still-higher-energy neutrinos, resulting from the interactions of extragalactic cosmic rays, could be observed with the Pierre Auger Observatory or with the dedicated experiment named ANITA.
It is thought that, just like the cosmic microwave background radiation left over from the Big Bang , there is a background of low-energy neutrinos in our Universe. In the s it was proposed that these may be the explanation for the dark matter thought to exist in the universe. Neutrinos have one important advantage over most other dark matter candidates: This idea also has serious problems. From particle experiments, it is known that neutrinos are very light.
This means that they easily move at speeds close to the speed of light. For this reason, dark matter made from neutrinos is termed " hot dark matter ".
The problem is that being fast moving, the neutrinos would tend to have spread out evenly in the universe before cosmological expansion made them cold enough to congregate in clumps.
This would cause the part of dark matter made of neutrinos to be smeared out and unable to cause the large galactic structures that we see. These same galaxies and groups of galaxies appear to be surrounded by dark matter that is not fast enough to escape from those galaxies. Presumably this matter provided the gravitational nucleus for formation. This implies that neutrinos cannot make up a significant part of the total amount of dark matter. Although their density is quite high, they have not yet been observed in the laboratory, as their energy is below thresholds of most detection methods, and due to extremely low neutrino interaction cross-sections at sub-eV energies.
In contrast, boron-8 solar neutrinos—which are emitted with a higher energy—have been detected definitively despite having a space density that is lower than that of relic neutrinos by some 6 orders of magnitude. Neutrinos cannot be detected directly, because they do not ionize the materials they are passing through they do not carry electric charge and other proposed effects, like the MSW effect, do not produce traceable radiation.
A unique reaction to identify antineutrinos, sometimes referred to as inverse beta decay , as applied by Reines and Cowan see below , requires a very large detector to detect a significant number of neutrinos. All detection methods require the neutrinos to carry a minimum threshold energy.
So far, there is no detection method for low-energy neutrinos, in the sense that potential neutrino interactions for example by the MSW effect cannot be uniquely distinguished from other causes.