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We're Close to Unlocking the Neutrino Enigma --"Could Be Matter and Antimatter Simultaneously"





Scientists around the world are being kept in suspense by the negligible mass of neutrinos, subatomic particles, one of the fundamental particles that make up our universe that could be matter and antimatter at the same time. Now, researchers from the University of Tokyo, in collaboration with a Spanish physicist, have used one of the world's most powerful computers to analyse a special decay of calcium-48, whose life, which lasts trillions of years, depends on the unknown mass of neutrinos. This advance will facilitate the detection of this rare decay in underground laboratories.

Neutrinos are neutral particles, so they are not affected by electromagnetic forces as they travel through space. Neutrinos detected here on Earth therefore trace a direct path back to their distant astrophysical sources. Additionally, these neutrinos rarely interact with other kinds of matter -- many pass directly through the Earth without interacting with other particles -- making them incredibly difficult to detect, but ensuring that they escape the incredibly dense environments in which they are produced. The image above shows one of the highest-energy neutrino events ever detected superimposed on a view of the IceCube Lab at the South Pole.

If neutrinos and antineutrinos are discovered to be the same particle, this would be the first known case of matter that is simultaneously antimatter. Additionally, it would generate an asymmetry that would serve to explain why there is no antimatter in the universe. Majorana neutrinos would have allowed for the creation of more matter than antimatter in the first moments after the Big Bang (for example, in neutrinoless double-beta decay, two electrons are emitted - the creation of matter - but no antineutrinos). After that, all antimatter would have been annihilated along with the majority of matter, releasing energy and leaving behind only the "excess" matter which can be observed in the universe today.

Neutrinos were discovered more than 60 years ago; however, scientists are yet to discover some of their fundamental properties, such as their mass (for which only the upper limit is known; this is around 3.6 x 10-36 kg), or whether neutrinos and antineutrinos are in fact the same particle.  The image below shows a neutrino event captured by Japan's T2K experiment. (


The_first_t2k_neutrino_event-4f072d7-intro (1)


An experiment that may offer an answer to the first of these questions is the so-called neutrinoless double beta decay. This occurs when an atom's parent nucleus decays into a daughter nucleus, gaining two protons, losing two neutrons and emitting two electrons. One example of this is the decay of calcium-48 (a very rare isotope of calcium with 20 protons and 28 neutrons) into titanium-48. This is the process that has now been analysed and modeled in unprecedented detail by scientists from the University of Tokyo (Japan). Their study is published in the journal Physical Review Letters.

"The half-life of this decay depends on two factors: the unknown mass of neutrinos (which are part of the process, even though none are emitted) and the characteristics of the parent and daughter nuclei. This implies that, knowing these nuclear characteristics, and once this decay has been measured experimentally in one of the underground laboratories working on it, it will be possible to determine the mass of neutrinos," SINC was told by Javier Menéndez, a Spanish researcher at the Japanese university and one of the study's co-authors.

The team's achievement has been understanding the nuclear part "in a reliable way" through extremely complex quantum mechanics calculations. These included as variables two thirds of the many protons and neutrons involved (to date, scientists had only managed to introduce one third of these particles) using matrices containing 2 trillion pieces of data. These operations were run using the world's fourth fastest supercomputer, the K-computer at Kobe's RIKEN Institute.

"Our findings will make it possible to directly obtain neutrino mass when the half-life of this decay is measured experimentally," says Menéndez. "Moreover, they suggest that the decay of calcium-48 is around half as long as what was previously thought (2 x 1025 years, rather than 4 x 1025 years). This improves our chances of observing it."

In any case, this is an extremely rare and slow decay, as it is mediated by two simultaneous weak decay processes. This means that it takes trillions of years to occur and is very difficult to detect. Laboratories working on this subject hope to observe one (which is due to decay very soon) in deep underground mines, far from any external "noise". Among the experiments trying to achieve this are CANDLES in the Japanese Kamioka Observatory (one of the winners of the Breakthrough Prize for Fundamental Physics for its research on neutrinos) and NEMO III in the Fréjus tunnel (France).




In the image above  neutrinoless double-beta decay of calcium-48 into titanium-48, two neutrons are lost, two protons are gained and two electrons are emitted. Neutrinos do not appear but form an "internal" part of the process. (B. Alex Brown)

After presenting their findings with calcium-48 (the easiest of the candidate nuclei to analyse), the researchers are now working on similar calculations for the neutrinoless double beta decay of germanium-76, selenium-82 and even xenon-136. The latter is the aim of NEXT, a Spanish project led by the Corpuscular Physics Institute (CSIC-University of Valencia), which is attempting to demonstrate in the Canfranc Underground Laboratory (Huesca) that the neutrino is its own antiparticle.

"The most interesting thing would be to confirm that neutrinos are not emitted during double-beta decay, as that would imply by physical principles that neutrinos and antineutrinos are the same particle; that would be a massive discovery, a Nobel prize for sure," stresses Menéndez. "If that happened, we could say that neutrinos are Majorana particles, because they would be particle and antiparticle at the same time. This property was proposed by the Italian physicist Ettore Majorana in the 30s."

The Daily Galaxy via FECYT - Spanish Foundation for Science & Technology



Does it not suggest that neutrinos are in fact part of Dark Matter?

@Jack, no it does not, since DM exhibits a) gravitational interactions both within itself and upon normal matter on large scales (neutrinos don't), DM has never been observed or even hypothosized to travle in straight lines, and DM is observed (by inference from gravitional interactions) as having enormous structure and size, and there is no evidence or theory of DM decaying or giving rise to the type of decay being observed by neutrinos, and if neutrinos where being generated/emitted by DM the high energy radiation would be easier to spot than fleas on Fluffy...just to bounce a few of the basics off the table.

What if neutrino oscillations were in fact due to an annihilation process with only an invariable mass transfer, or only a momentum transfer...?

@Michel, then it wouldn't appear as a particle (which on the quantum level is actually a state of waves), and I know of nothing even remotely suggesting "only" a mass or only a momentum transfer (rather difficult to even imagine an oscillation consisting solely of mass since mass in motion posses momentum by default in any state and motion infers energy). Nor does anything in the analysis being discussed suggest such a quirk of quarks (sorry 'bout that). Aside from the obvious violation of "only" a "transfer" during an "annihilation", And in what manner would that connect to DM (if you're ref'g to the previous confab)? Not meaning to sound trollish, your what if just doesn't match up to the known observational data of either DM or neutrinos. Not even if this latest potential discovery is verified. We already have the impact traces that discount/refute such a proposition. On the other hand, given what we do know, or presume to know, it is not a far extrapolation from the duality of waves and particles for the the neutrino to be both at the same time, or neither at the same instant, and hence it has the potential to exist without self-destruction. Thanks for not suggesting it might be result of electromagnetism!

I'm not referring to DM. I am not saying that it is an annihilating process, just evoking the possibility.

The problem is that the nature of the neutrinos is mostly unknown, apart that they have a proper mass, a spin, no apparent electric charge and a couple of other theoretical parameters, which are used mathematically to solve some problems. Neutrinos are the only stable massive elementary particles with no electric charge.

Neutrino oscillations production is analog to scattering...

The fact is, there is no sign of majorana neutrino and no sign of neutrino annihilation...

??? I just wonder... :o)

Dismissing any connection to DM, and doing the math found in the wiki you cite, and accepting there "is no sign of majorana neutrinos..and annihilation".... could lead a person to wonder and postulate on a number of scenarios. But the language you used originally (what if...oscillations WERE IN FACT DUE TO AN ANNHILIATION PROCESS // emphasis for clarity) is an arguement against itself. You would not be describing an event or particle consistent with the wiki article you mention, and your speculation is not just inconsistent with the math describing neutrinos/neutrino decay, it is in conflict with all other known physics and your own suggestion. In your scenario, an entirely new physics would need to be invoked that would require the basics, the very fabric of all physics, to become random.

Thinking outside the box, coupled with experimental investigation, did lead to this current potential discovery/explanation. However, it doesn't breach all known physics but corresponds to the evidence of the experimentation and theoretical modeling.

What I'm saying is, if it doesn't waddle, quack or otherwise look like a duck, it probably isn't a duck and most likely isn't a 10 legged elephant, either!

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