# Symmetry for dummies!

Hi,
as I said, I will continue with the explanation of what I mentioned in some earlier posts. Today I will try my best to learn you what physicists mean when they say something about “symmetry”.

First of all, when you say symmetry you probably mean that it is the same on both sides.

On the next picture you have some shapes with the right and left “lines of symmetry”.
This means that you can flip them around this line and they will be exactly the same pictures.

Square has more than one line of symmetry, there are four of them [1].

This is what we think as symmetry but physicists use it in more kind of complicated way.

When somebody makes experiment with coca-cola and candy [2] it will explode. And it will explode in New York, Prague, under water, upside down if you do it properly and even in space. This is symmetry, it does not matter where you do the experiment. But it does matter what you do it with, if you would have used water instead of coca-cola, or chocolate bar you would see that there is no symmetry [2.5]! Because it is not going to work!

When we talk about particles we can say that there is a symmetry in them, for example you can have 3 quarks, labeled as Paul, Rick and Nick. It does not matter which one you will use, because all of them have the same properties! This is symmetry all quarks are same, all electrons are same and so on.

There is a symmetry in fundamental forces. For example in strong nuclear force there is symmetry in quarks and their colors [3]. It does not matter how you label one of three quarks, it can be red, green or blue.

Also charged particles are created in pairs. This means that you have to conserve the charge so if you create electron you must create positron or something else with positive charge.

Only weak nuclear interaction of all fundamental forces has special kind of symmetry. Weak force is the only force which makes difference between particles which are right and left handed.

Such a particles  are in pairs:

• quark u ←→ quark d
• quark c ←→ quark s
• quark t ←→ quark b
• electron ←→ electron neutrino
• mion ←→ mion neutrino
• tauon ←→ tauon neutrino

This is also called the breaking of parity.

So weak interaction breaks symmetry and behaves differently with right and left handed particles while other forces do not do this, take for example gravity, everything is attracted by it and it does not matter if it is quark u or quark d.

Of course those particles are diametrically different their mass varies a lot, but this is only because of what is called: Higgs field, and I am going to talk about it another time.

Dragallur

[1] Star has 5 lines of symmetry, triangle has 3 and arrow only 1.
[2] I do not know if it is in English mentos.
[2.5] This is also called “broken symmetry” if it would not be broken, in this analogy anything would work as the mentos candy and there would be no difference between coca-cola and oil.
[3] Quarks have colors as I mentioned in last post and also in post about strong nuclear force.
[4] Maybe you remember from chemistry how you were filling the orbitals with pairs of electrons: ↑↓. Those arrows mean that one electron has negative and second positive spin (but still the same value: 1/2  .. -1/2)

# The riddle of DARK MATTER! (Part 2)

Hi,
about three days ago I was asked by the writer of “Oopsmymistake” to update about dark matter, so today I decided to write something more about it, here you go.

Last time I talked about dark matter as stuff that fills about 25% of all matter in whole Universe but we can not feel it and the only way to observe it is by its gravitational effect, for example it is extremely important in whole galaxies.

Now there are some things that I did not mention because actually there are more things that we can deduce from its behavior.

As I said, it is assumed that dark matter is composed of new kind of particle/s beyond standard model.

Lets assume that this is right, now this particle does not react much as we know, it has to be electrically neutral, otherwise it would react through electromagnetism and we would be able to observe the photons which would come out of the interaction.

Also dark matter still exists which means that it has to have half life at least the age of Universe (top and bottom quarks for example do not form anything because simply they are not here, they have too small half life).

We know that it does not interact much, otherwise it would concentrate in the middle of galaxies and not all around. So dark matter can not interact via strong nuclear force.

Now this kind of hypothetical particle is called WIMPWeekly Interacting Massive Particle.

It is assumed that the mass of such WIMP is about 10-1,000 GeV which is roughly around Higgs boson and other bosons like W and Z.

The amount of WIMPs with such a energy almost perfectly corresponds to the real amount of dark matter. Also model of super-symmetry predicts such particle with the properties we know now. It is definitely more complicated but it is called the WIMP miracle, while it could be just coincidence.

Scientists think that with this model WIMPs should interact with Higgs boson which would create something we call: “The Higgs portal” because Higgs boson would be the particle through which we would be able to observe whole dark universe (the portal between standard model and dark matter).

Of course particle physicists designed special detectors to detect WIMPs. There are two main way to do that, first is cryogenic, which is the detection of heat made by WIMP interacting with some super cooled element and the second one is to measure flash of light during interaction of WIMP and liquid xenon or argon. Such detectors are buried deep under Earth so that normal radiation does not disturb it.

Approximately in the volume of cup of coffee is always one WIMP and it is assumed that they travel at the speed of hundreds of kilometers per second, which means billions of them whizzing through you every second. Also about 10 interactions of WIMPs happen every year with atoms in your body (this is kind of similar to neutrinos).

Dragallur

PS: if you did not understand some terms I will mention them in next posts: Standard Model, Higgs boson and so on..

# How does particle accelerator work?

Hi,
so as I continue with the book I am reading right now about particle physics I will write about the basics behind particle accelerators.

There are several types of accelerators, they can be divided into groups by either the energy they can create or what kind of particles they are colliding, some accelerators even do not have this circle but they rather just hit some big target.

Inside accelerator you will surely have some great detector which is going to collect the data for you. In Large Hadron Collider (LHC) in CERN there are two main detectors: ATLAS and CMS. There are two so you can compare their results.

Those detectors are huge, ATLAS has 21 meters in diameter.
Then there is the tube in which you have got those particles running. In LHC there are protons in both direction. Those protons are taken from little bottle with hydrogen, this bottle would serve for billions of years because there are 10^27 particles inside.

When you take these particles you will speed them up. The particles in LHC those are protons are separated to groups. Between each group is seven meters of vacuum. In each of those clouds of protons are 100 billions of protons. This cloud can get thin as 1% of millimeter right before collision.

Protons are all positively charged so it is hard to keep them in the cloud. Because of their charge, you can speed them up using magnets. To get the top speed you have to use extremely strong magnets, which means electromagnets [1]. Those magnets will speed the particles to 99.999996% of speed of light, so obviously that is where theory of relativity comes to role, for example those particles are not spheres but rather pies because of their huge speeds — effects of relativity.

After you speed up those particles you are going to collide them. This happens at the detectors which are going to measure all the stuff that is flying away from the collision. You may identify particles by their direction of traveling, by this you may know their charge. Also how deep they were able to fly. Mions for example have longer life times than most other particles so they are able to fly through the accelerator, while bosons w and z or tauon have such a low life time that they wont fly very far and most of the time you are going to observe their products rather that those particles alone.

Dragallur

[1] Electromagnets are magnets powered by electricity because when you have electricity, it creates (electro)magnetic field. This gets stronger the stronger is the current. In particle accelerators it can get so strong that the magnets would melt at a moment because of friction with electrons, that is why they must be cooled to little over absolute zero, using liquid helium.

Only picture

# 4) Particles: Hyperons

Hi,
I will talk about hyperons. Hyperons are not fundamental particles because they are made up by quarks, like neutrons or protons.
(to see what are quarks check this post: https://dragallur.wordpress.com/2015/05/03/3-particles-quarks/)
They are in the group of hadrons. It is group of particles that are made up by quarks so in this group are also Pions which are in the smaller group of mesons.
Btw. mesons are particles that are made up by pair of quark-antiquark.
While hyperons are in the group of baryons = particles with three quarks.

So the strange thing about them is that they have to have one strange quark so they can be hyperons. The most “common” one is similar to proton or neutron because he is made up of up, down and strange quark and he is called Lambda. There are twelve of them with different combinations of those three quarks, one of them, Omega has only strange quarks.

Ok, thats about it. They have also attribute of really fast decaying because strange quark is not very stable so they can not be found except in Hyperon stars. Those are heavier neutron stars in which hyperons wont decay because they have no space and gravity will hold them.

Dragallur

# 3) Particles: Quarks

Hi,
I have been writing about quarks a lot so now I would like to shortly summarize what they are.
Quarks have been discovered when scientists saw that paths of particles traveling close to neutron are distorted by some weak electromagnetic field. Then they discovered that neutron is neutral but it contains particles which are not neutral: quarks.

If I told you that protons and neutrons are only made up of three up and down quarks  you could easily figure out what is inside them. Proton´s charge is +1 which means there has to be 2 ups and 1 down because UP(charge)=+2/3 DOWN(charge)=-1/3 === 2*2/3+(-1/3)=+1. While neutron is made up of two downs and one up which equals to 0.
As you can see from the table there are six types (flavors) of quarks. I talked only about two of them because they are much more common then charm, strange, top and bottom. The reason why those four are less common is that they are extremely heavy compared to up and down quarks and they will decay into up and downs. Up and downs can not decay to anything which makes them stable. Even then it is thought that proton (uud) can decay.. I talked about it earlier so you can check my other posts.

Flavor is one attribute but there is another. I mentioned it in post about strong interaction and it is color of quarks. There are three “colors”: RGB — red, green and blue and antired, antigreen and antiblue. Those colors always have to add up to white color. There are lot of combinations which can do this – RGB, antiRantiGantiB, blue and antiblue, red and anti red… and many others

It would be far too easy without gluons which are holding quarks together.
They are usually drawed as a short string between quarks. The thing that they do is color changing. They do it at two points: when they enter and when they leave quark.
There is hypothetical astronomical object called Quark star which should be made up of free quarks. Also it is thought that right after big bang there was state of matter in the Universe called quark-gluon plasma… soup of free quarks and gluons. We are not yet able to create this because it probably needs extremely high temperatures.
On the left is a picture which compares mass of quarks. On the botom you can see grey proton and really small, red electron. Top quark is the largest one.

Particles which are made up of quarks are sorted into different groups: mesons and baryons you can see on the picture what they can look like and how colors add up to white.

Dragallur

# 2) Particles: Neutrinos

Hi!
I am back again with particles post. I was thinking if first should be about electrons or photons and then I realized that neutrinos are kind of really special and fun so I will start with them.

Neutrinos are small particles in group called leptons.
They can be created by thermonuclear reaction which is happening in stars so there are huge amounts of them flying in the Universe. Actually there is so much of them that every second millions of them will pass through every cm^2 of your body. Before it was thought that they are massless which would mean that they are able to travel at the spead of light which is not true, they have some mass but it is not much.
It is really hard to detect them but there are machines that can do that. I think that one of them is built under ice in the Antarctic continent. Even when there is so many neutrinos it can detect only extremely small fraction of them (I would not try to quess the numbers).
Neutrinos also dont interact very much so they are able to pass through whole earth without slowing down.
Supernovas are also really great source of neutrinos but they do not occur that often.
On the Earth we create it in nuclear reactors and neutrinos are also made inside the Earth because as I said in some previous post when material is beta decaying it will release neutrinos.
In the year of 2011 there was mistake when measuring the speed of neutrinos. Computer counted that traveling neutrino was able to travel distance 60 nanoseconds faster than light which is not possible. Soon they luckily knew where was the mistake.
Dragallur

# 1) Particles: Prologue

Hi guys!
I am back with probably short post because I am lazy and tired these days. I know I wanted to start something about triangles but right now I am not that excited for it so I will make some posts about particles. I talked about some before but I have never explained what the hell are quarks for example.

So first of all… particles. Well we think about them like small stuff that is everywhere and everything is made up of it. That is right.
So I will start with molecules, easy peasy those are just two or more atoms made up together.
Atoms are (small), there is some stuff in them but first of all there are “kinds” of atoms, substances and that is Hydrogen, Helium, Oxygen, Carbon. They are made up all from the same things but with different amounts. Atoms are made up of core and shell. Usually, you wont do anything with core. It is very stable and not interacting. In our organism there are only changes in molecules. That means that some atoms will move somewhere else and that will change molecules properties.
Shell is made up of electrons. Electrons are NOT made up of something else, it is just primal stuff. Electron belongs to group of particles that are called elementary particles. It´s sub-group is called fermions and its sub-sub-group is leptons which are really small and light.
Core is made up of neutrons and protons. As I talked about them in four fundamental forces series those are particles (sub-atomic) that are hold together by strong force. Anyway protons are positive and neutrons neutral.
There is huge experiment going on in Japanese which is trying to proof that protons are decaying. Its problem is that one proton has half time about 10^31 years long. They did nice trick so they do not need to wait so long by monitoring ultra clear water. There are thousands tons of water and their machines are able to detect any proton decaying to photons.
Photons are also elemental particles but their sub-group is special for particles that are carriers for fundamental force: photon, gluon, bosons but not graviton because he is only hypothetical. Photons are massless which is why they can travel at the speed of light.
At last for review there are quarks which are elemental particles, even fermions like electrons but they are in special group for quarks.
I actually read something about quarks not being elemental (only hypothetical). It was said that if they are not elemental we can not be sure that there is unlimited number of smaller and smaller particles.

This was just a short preview of what I will write about next time.
Dragallur

# 5) Four fundamental forces: Strong interaction

Hi there!
I am back again! I was very sick with great temperatures but now I am alright with idea what to write about so I am bringing probably the last post for four fundamental forces today with strong interaction as the strongest of all forces.

Again on the left I have here proton. There are two parts of strong interaction, first is color force which is the stronger one and it holds particles, like hadrons (particles made of quarks) together. You probably heard of colors of quarks, there is green red and blue (RGB) and in such particle like proton or neutron those colors always have to add up to white color. If it would be antiparticle it would have anti red, anti green and anti blue.

Again on left you can see how these colors add up to white. Well what happens is that there is gluon, particle which is carrier for strong interaction and it jumps from quark to quark and when it touches it changes its color. There is great animation in this video, I recommend to watch it: https://www.youtube.com/watch?v=BNDOSMqGLlg
This color force is extremely strong so it does not let quarks to go apart. It is even that strong that when you break it new quark will be created from that huge amount of energy! Scientist think that right after big bang when particles were really fast and close to each other there was state of matter called quark-gluon plasma which was kind of soup of quarks and gluons. It is hypothetic and it was not yet created in LHC or somewhere else.

There is that second part of strong interaction called: nuclear force. I am not really sure about it, but anyway you maybe wondered why does nucleas exists when protons(+) should repell each other and that is made by particles called pions which are carrying quarks around and they are creating reaction which is attractive.

On the end, pions are particles made up of two quarks but one of them has to be antiquark so they looks like this:
There are three types of pions and those are Pi+, Pi-, Pi 0. Their life time is incredibly short and they are decaying to neutrinos or gamma rays.

That will be all,
Dragallur