Before I start to answer this question, I will start with a little history. Here lies the answer why detection of neutrino is so important. We are very curious in nature and I sometimes wonder was there a person who never looked at the sky and wondered about the stars. We have always thought our life is somehow related to them and that really give birth to the science of astronomy.
We have always wondered about them, what they are made of, do they die like us or they live forever? Those question made us seek the answers and helped us to unlock the layers of the heaven one after another. Since the ancient times, the sun was a matter of wonder to us. Sometimes we even put it in the place of God. It was a hanging debate of centuries that is it the center of the universe or the earth is. But with time the sun proclaimed its place the center of the solar system and with technologies we observed it more than ever.
In the beginning of the 20th century Edward Pickering and his group started classifying the stars according to the spectra and then we got to know about the outer layer of the stars as those spectra were form in the atmospheres of a star but that doesn't give us any clue about the interior of the star and what is going on inside. Thanks to atomic theory and quantum mechanics, it was answering the questions of emission and absorption lines and so many other phenomena going on inside an atom. It was Hans Bethe who answered perfectly what is going on inside the sun or any stars and it made sense.
Star formation
We can compare star with football. The only difference is football has empty space inside but stars don't. Ofter stars are called as firey balls. So, the question is where is firey ball came from? Does it have an origin or in simple words does it born and die like us? Well, yes it does.
In the interstellar space, there are clouds and gases floating around. But these gases are so cold and by telling so cold I mean below zero. The gases here are mostly hydrogen and carbon dioxide. Because of so low temperature the atoms stick together and make molecules and in this way the density increases and we know as the density increase pressure increases and that causes the temperature to increase. Gravity does the job here. As the gases become denser and denser, gravity brings them closer and the center is densest. Ok, let us think of an analogy.
If you have ever tried to get out of the gate after a football match, you will see the crowd is pushing and as the pus comes from all sides the guy in the middle will feel the push most. Gravity does the same thing, it brings the gases closer and closer and it becomes dense in the center. Because of the difference of density level between the center and the outer cloud, the center breaks into some fragments and each of them has around 10 to 50 solar mass. Now as each of the fragments has separated itself from the others, it will have its own gravity and angular momentum. As it has its own angular momentum, it will turn the irregular shaped fragment into a rotating disk. This stage is called a protostar.
The loosely bound matter will fall into the disk because of the rotation and make the temperature and pressure high. At one moment the temperature will be so high that thermonuclear fusion will start in the core and it will create a stellar wind not allowing any matter from further falling. This is how a star is born. The video below can help with what I just said up.The Fuel for life of a star
As I told that gravity is compressing the star inward and as fusion creates outward pressure to balance the star. But it can happen in two ways. For sun-like stars, it happens through p-p chain reaction and for massive through CNO cycles. I won't describe CNO cycles as for today's topics it's not that important.
So, the basic thing is two protons collide and they make a deuteron (happens in two steps). In the first step, they make diproton and then happens beta decay, creates deuterium, neutrino and positron is decayed. This reaction is so slow as most of the time it goes back to two protons. Later the positron annihilates with an electron and emits two photons, The deuterium later collides with another proton and make a helium3 isotope. This helium isotope collides with another helium3 isotope and turns into a helium-4 nucleus and neutrinos are released as well. If you want to know it in detail follow @maticpecovnik's blog. He wrote it in more details and more elaborately.
Here our main purpose is to deal with those released neutrinos. A photon needs thousands of years to the surface and then it travels to us. So, from here we can know only what happened thousands of years ago in the interior of the sun but neutrino travels without any restrictions. So, by detecting neutrinos we can really know about what is going on inside.
Properties of neutrinos and detection
Neutrinos are a very elusive elementary particle. It has a very small cross-section that means it rarely interacts with anything. Its an elementary particle of lepton group. Other particle in this group is electron, muon, and tau. It is an almost massless particle and very abundant in the interstellar medium.
During 1970, Raymond Davis put an attempt to measure the neutrinos coming from the sun. His laboratory was around a mile underground in South Dakota. As neutrino interacts so barely with other matters. it was ensured by the detectors to measure the neutrinos which take exactly eight minutes from the sun.
His device contained around 65000 kilograms of cleaning fluid and 10000 gallons of Carbon tetrachloride. The idea was as the neutrino collides with the chlorine isotope (37Cl17), it will produce a radioactive argon (37Ar18)isotope with a half-life of 35 days. One thing is so important to remember is the threshold energy should be lower than the energy of neutrino release during the p-p chain reaction..
= 37Ar18 + e-Once in every few months, he and his colleagues use to collect the amount of argon produced and the amount is measured in SNU (solar neutrino unit). 1SNU is same as 10-36 reactions per target atoms per second. The theory suggests of capturing a neutrino every day while in the experiment it happens one in every two days. So, there is a huge disagreement between the theory and experiment.
The other detectors for neutrino detection has also confirmed this disagreement. Kamiokande in Japan which works on the method of detecting Cerenkov radiation, when neutrino scatters the electrons and as a result electron moves in a speed faster than light in the medium. They used 50000 tons of pure water and detected half of the suggested neutrinos predicted by the theory.
Soviet-American gallium experiment and Gallex as well find the same problem. Their method was as neutrino interacts with gallium, it turns into germanium
= 71Ge32 + e-The solution
The problem can be approached in two ways. Firstly, maybe the solar model is not correct or something happens to the neutrino on its way to earth. Firstly, the solar model was re-examined and that includes the rate of nuclear reaction, the opacity, the structures of the interiors but there was still no progress in solving the problem.
Then a group of scientists proposed a model and according to them, there is nothing wrong with the solar model. The thing what happens is the neutrino changes in other types. All the neutrino released in the p-p chain reaction are electron neutrino but there exist muon and tau neutrino in nature as well. So, along the way from the sun to earth, it changes from electron neutrino to other types. As the detectors are only sensitive to electron neutrino so we get less neutrino than predicted. This effect is known as Mihietev-Smirnov-Wolfenstein effect. This is an extension of the electroweak theory. So, these transition happens because electron neutrino interacts with electrons on its way to the surface. So, they oscillated among different flavors.
One of the consequence of this theory is that neutrino should have mass. This transitions between different favors are not possible if the neutrino is massless. This theory was later proved by super Kmiokande detectors in 1998 while they were observing neutrinos created by cosmic rays on earth's atmosphere. In 2002 Devis and Masatoshi Kosiba won Nobel prize for their contribution in detecting neutrino. That's all for today. Have a nice time everyone and steem on.Reference
1. Carroll and Ostlie, An Introduction to Modern Astrophysics
2. Olga Atanackovic, General Atrophysics
3. Mirjana Vukicevic, Theoretical Astrophysics
5.math.ucr
**StemQ Notice:** *This post was originally submitted on [StemQ.io](http://www.stemq.io), a Q&A application for STEM subjects powered by the Steem blockchain.*
This is the kind of knowledge that will marinate in the back of my brain and my mouth will blurt out at the most awkward point during one of my uncle's racist rants over Thanksgiving dinner.
Thanks for posting!
Hahahahaha lol. You are funny dude. Thanks for commenting
Actually, the second guy is the muon neutrino, not the mi neutrino.
As a side effect, the fact that neutrinos are massive implies physics beyond the Standard Model. Indeed, we need to add extra particles to be able to model neutrino masses. We hope that the LHC will provide some guidance with this respect.
it is also important to keep in mind that neutrino physics is still puzzling. For instance, the MiniBooNE and LSND experiments still report neutrino numbers disagreeing with the theory (see here for more information).
Thanks Lemouth. Most of the times i make these mistakes even with pion as well :p I will fix it :)
Was not aware of the information. Thanks for the help and thank you for visiting my blog :)
The pleasure of reading you is always for me. Even if those days it is hard because of a veryyyyy lagging internet connection (traveling).
Thank you so much :)
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