tau neutrino

Why Neutrinos are so Weird

If you held out your thumb, every second about 65 billion neutrinos will pass through it. Besides photons, neutrinos are the most abundant particle in the universe, and by far the most unique.

The existence of the neutrino was first theorized by Wolfgang Pauli, after noticing how energy didn’t seem to be conserved in beta decay. He believed that the missing energy was being carried away by some “invisible” particle. He would later say “I have done a terrible thing, I have postulated a particle that cannot be detected.”

Although elusive, neutrinos can be detected, but it requires sensitive, and often massive detectors. After finding that neutrinos came in three types: electron, muon, and tau, a problem seemed to emerge. Electron neutrinos are created all the time in the Sun, as a by-product of nuclear fusion, but they would always find only a third of the total number of electron neutrinos they were expecting. So, where did the missing neutrinos go?

It turns out, neutrinos actually oscillate back and forth between the three different types. So, by the time the neutrinos from the Sun had reached Earth, two thirds of them have turned into muon and tau neutrinos. This discovery was especially surprising, since everyone thought neutrinos had no mass, like the photon. The fact that neutrinos could change in-flight implied that they could experience time, and due to special relativity, this means they must have mass.

While that mystery has been solved, we still have plenty to learn from these strange particles. Exactly how much do they weigh? Although we know they must have mass, they are so light, we can’t tell how much. Since they have no electric charge, is a neutrino its own anti-particle? Are there more than just three types of neutrinos? Answering these could help us uncover some of the biggest mysteries in physics today.

Tau Neutrinos Going Faster Than The Speed of Light?

Nine days ago, BBC broke the news that physicists at CERN in Geneva, Switzerland may have got a tau neutrino to go faster than the speed of light. I’m sure that a lot of you have been bombarded with news reports about this, but I’m also sure that a lot of you don’t know what a tau or a neutrino is, so first of I’m going to explain that to you. In the standard model, which is a model that illustrates all of the basic particles that we know of today, there are quarks, leptons and bosons. Quarks are well quarks. There are 6 types of quarks: up, down, strange, charm, top and bottom quarks. They each have their own distinctive properties, but up and down quarks are the most common, as they make up protons and neutrons. The bosons are the forces, there’s the photon, gluon and two weak forces (there is also the predicted Higgs boson which gives particles mass, but it has not been discovered yet). And finally there are the leptons: the electron the muon and the tau and then their respective neutrino versions (the electron neutrino, the muon neutrino and the tau neutrino). You have probably heard of electrons before, they are tiny particles with electric charge that along with protons and neutrons make up an atom which then makes up all of matter. Electrons have 2 big brothers, the muon and tau which have larger masses than the electron. Each lepton has it’s own neutrino version, the election neutrino, the muon neutrino and the tau neutrino. Neutrinos are created in types of radioactive decay and nuclear reactions. Neutrinos have a very small, non-zero mass.

Physicists at CERN in Geneva, Switzerland have been sending neutrinos from Geneva, Switzerland, through a tunnel in the alps into Italy where they are collected and observed at the Italian National Institute for Nuclear Physics’ Gran Sasso National Laboratory. A couple of weeks ago, neutrinos being sent from CERN to the Italian National Institute for Nuclear Physic’s Gran Sasso National Laboratory arrived there 60 nanoseconds faster than the speed of light would have predicted them to. The speed of light is 186,282.397 miles per second, or 299,792,458 meters per second and according to Einstein’s theory of Special Relativity, nothing can reach or go faster than the speed of light, a theory that has been confirmed. A tau neutrino arrived at the Italian National Institute for Nuclear Physic’s Gran Sasso National Laboratory 60 nanoseconds before it should have. Physicists at CERN have been recreating this experiment many times, only to find the same result, they have also been going over this data many times to check for errors, but haven’t found any. They have given themselves an error margin of 10 nanoseconds, meaning that it arrived in Italy between 50 and 70 nanoseconds before it should have.

However, this isn’t the first time that this has been reported. A couple of years ago at Fermi lab in Illinois, USA, physicists reported that they found similar results. However, they gave themselves such a large error margin, that they concluded that this was a mistake. Because of this, you probably never heard about it.

If this is indeed true, this would be a monumental discovery. This wouldn’t change how the universe works, but rather it would change how we think it works. Einstein’s theory of Special Relativity, which has been worshiped for over a century now by Physicists all over the world, maybe incorrect. However it is tough to believe that his theory is incorrect because of Time Dilation. Because the speed of light is the ultimate speed limit and is not relative, it is always constant, time slows down as you move faster. I talked about this in a previous article, but in short, the closer you go to the speed of light the slower time progresses for you relative to those on Earth. If you go reach the speed of light (which according to Einstein is impossible) time will stop. If you go faster than the speed of light (which according to Einstein is also impossible) time will go backwards. The effects of time dilation have been confirmed. This makes the fact that tau neutrinos went faster than the speed of light all the more baffling. One theory as to why this happened is that the tau neutrino may have traveled through another dimension to get there earlier than it should have. String theory (which I will talk about in a later post) predicts that there are 11 dimensions, 7 more than the 4 dimensions that we currently live in (left-right, up-down, back-forth and time are the dimensions that we live in).This means that there may be other dimensions for us to travel through.

But what does this mean for science? Will we have jetpacks? Will be able to travel to galaxies millions of light years away? Maybe. We probably won’t have jetpacks, we will have something far more exotic than that. We may have the ability to effectively teleport to other places by traveling through other dimensions. We may be able to travel to other planets in galaxies far, far away if we deplete Earth’s resources, though I wouldn’t count on it, so don’t go turning on all of your lights and leaving them on for a couple of days.

Still, this hasn’t been confirmed. We don’t know that the tau neutrino traveled faster than the speed of light, we are just very sure. A lot of you probably think that it didn’t travel faster the the speed of light, and there is a valid argument for that, and you may as well be right. But a lot of you probably think that it did travel faster than the speed of light and you may also be correct. How ever it isn’t debatable that if this is true, it would be a huge discovery. What do you think?

Possible explanation for the dominance of matter over antimatter in the Universe

Neutrinos and antineutrinos, sometimes called ghost particles because difficult to detect, can transform from one type to another. The international T2K Collaboration announces a first indication that the dominance of matter over antimatter may originate from the fact that neutrinos and antineutrinos behave differently during those oscillations. This is an important milestone towards the understanding of our Universe. A team of particle physicists from the University of Bern provided important contributions to the experiment.

The Universe is primarily made of matter and the apparent lack of antimatter is one of the most intriguing questions of today’s science. The T2K collaboration, with participation of the group of the University of Bern, announced today in a colloquium held at the High Energy Accelerator Research Organization (KEK) in Tsukuba, Japan, that it found indication that the symmetry between matter and antimatter (so called “CP-Symmetry”) is violated for neutrinos with 95% probability.

Keep reading

Flavour vs Family vs Generation 

You have your quarks and leptons: 

There are 12 flavours. You can think of it as 12 types since the word flavour doesn’t have a significant meaning, it’s just refering to the 12 different types of quarks and leptons. There’s 6 quark flavours, 6 lepton flavours, for a total of 12 flavours. You can also refer to the neutrinos as 3 neutrino flavours, since there’s 3 types of neutrinos. 

Then you got your generations, aka families. They mean the same thing. See the top quarks is just a heavier version of the charm quark which is just a heavier up quark, so the up quark is part of the 1st generation (orange background), the charm is part of the 2nd generation (green background), the top is part of the 3rd generation (blue background). 

Same with the other ones, the bottom quark is a heavier strange quark is a heavier down quark; the tau is a heavier muon is a heavier electron (as for the neutrinos, we’re not too sure about neutrino masses yet). There’s no difference in interaction (again with exceptions) or properties like charge or spin between generations, they’re just heavier and less stable (ie. will easily decay) versions of the first generation. Because the 2nd and 3rd generations tend to decay into the 1st generation, protons and neutrons are made of up and down quarks, with an electron orbiting it (as oposed to a muon or tau) (again the neutrinos are weird). 

The interesting thing about Muons, Muon Neutrinos, Tau and Tau Neutrinos, is that they have a life (half life) of such short duration… billionths of a second, that it is a bit weird to consider them as useful particles… i.e.  stability is all rather important when seconds and minutes matter a lot.

Weak interactions

Weak interactions between particles are mediated by three types of currents. Two of these currents are charged: the W+ and the W-. The third current, Z0, is neutral.

Weak interactions involve the three lepton families (electron and electron neutrino, muon and muon neutrino, tau and tau neutrino) and the three quark families (up and down quarks, charm and strange, top and bottom/beauty). Each family is called a weak isospin doublet. Isospin is a quantum number similar in form to spin, but related to strong or weak interactions. In each lepton family, for example, the neutrino has isospin T = 12 and the fermion has isospin T = -12. In this manner, the doublets are formed by  gathering  two leptons of opposite isospin:

Considering interactions that involve only two initial particles, there are laws that determine :

  • Which couples of particles can interact with one another, and by means of which current
  • What are the possible “outcome” couples one can find after the interaction.

The following diagrams summarize these laws.

States connected by the W boson, or the charged weak current:

States connectect by the Z boson, or the neutral weak current:

Let me tell you about something super cool called ‘neutrino oscillations’

Basically there are three ‘flavours’ of neutrinos: electron neutrino, muon neutrino, and the tau neutrino, and while travelling in space a neutrino oscillates through the three types. 

A neutrino that left the sun as an electron neutrino may be detected on earth as a muon neutrino, or a tau neutrino. In fact the solar neutrino problem was a mystery (now solved) where the amount of detected electron neutrinos from the sun was waaay less than the amount predicted. Turned out it was because the neutrinos changed flavours on their trip to the earth.

This also proved that neutrinos aren’t massless as previously believed, but then that’s getting into eigenstates and quantum field theory and stuff