Neutrinos, the Superstars of particle physics.

Neutrinos are the superstars of particle physics.

Indeed they are the subjects of many news articles and succeed in maintaining the mystery around them which makes us wanna know more about them.

How can such a tiny particle creates so much fuss and excitement about it? What's so special about neutrinos? Why do they play hide and seek with us?

What are they?

Neutrinos are particles of matter. As I mentioned before there are two types of particles:

particles of matter called fermions

particles of forces called bosons cf article...

So, neutrinos are fermions and more specifically, they are leptons.

When were they discovered?

Neutrinos were discovered in the 1930s. It is quite a different story than other particles. They were discovered because of a bug.

At that time people were starting to understand more and more about particle physics.

Electrons wasn't a mysteries anymore, nor were protons, neutrons and a bunch of other particles.

One of their favorite experiment was the b decay (that tells us a lot about nuclear physics):

No, no, don't be like...0.0 what's that...
It's actually super easy to understand. The beta decay happens when a proton p meets and electron e-, those particles annihilate and create a neutron and?… but what is that? Let's take a look at that equation for a second.

One of the most important rules in Physics is that energy must be conserved.

That means that for any transformation, there has to be the same amount of energy at the beginning than at the end.

But here physicist could calculate over and over again, night long, there was always something missing. The energy was not conserved, but instead they realized there were more energy in the beginning than in the end!

JEZZ! Where did that energy go! 'Cause no, it simply cannot disappear!

Wolfgang Ernst Pauli postulated that this question mark should be an extremely light and neutral particle and in 1933 Enrico Fermi named it neutrino (which mean in Italian little neutral one). What a cute story!

The equation was finally completed!

Where do they come from?

Well they don't really come from your garden. Though they are everywhere and probably thousands go through you everyday! Don't worry you are totally safe. :) I'll talk about it in the next part.

They need cataclysmic event to be produced, event that are so powerful that they destroy everything around them.

Such event are Supernova, i.e. explosion of huge stars.

                                                                            Supernova

They are also produced by black holes.

Once they are produced they travel and meet us. They can travel for millions of years without meeting anything!

How can they be detected?

As I mentioned earlier thousands of neutrinos go through you and me everyday. And there's nothing to worry about. Why is that so? Because neutrinos barely interact with anything. They are so small that they go through the empty space between the nucleus and the electrons (pictures).

They rarely hit another particles. Now you must think, fiu, I didn't want to get a neutrino cancer. Well you won't! But the fact they don't interact makes them extremely hard to detect as well.

For that purpose, scientists worked out huge installation that look like big swimming pool hoping to detect neutrinos!

                                                                      Kamiokande

And it worked! They even detected almost ten neutrinos at the same time!

(Most of the time they are happy when they detect one neutrino a week...)

Why are they so strange?

They are strange indeed. Not because they are small. Not because they are light.

First of all some scientists thought neutrinos might be tachyon which means they can go faster than light! It turned out they are not.

But something else make them very interesting:

They change flavour. Basically there are 3 types of neutrinos: electron neutrinos, muon neutrinos and tau neutrinos.

And the weird thing is that an electron neutrino can decide all of a sudden to become a tau neutrino. It's like wearing a pink dress and decided all of a sudden to make it blue.

And no one can explain it so far!

What's so special about them?

If you're not convince yet neutrinos are hella cool, let me explain myself a little bit more.

Neutrinos are particles that we don't  really understand. We know they have a mass, but that mass seems to be smaller than anything we know, same for their energy (it is extremely low).

Beside their flavour oscillation has never been seen with any other particles.

Those particles are still a mystery to scientists. And that's awesome because studying them is going to help the scientific community unravelling some mysteries of the Universe such as the early ages of the Universe...

Sophie incognito