The secrets of universe

Introduction

When my friends ask me what i like about chemistry i always tell them that every material has its own features and its own story to tell.

For instance, when we work with pipelines manufacturers, we have sometimes to deal with cast iron.

If this material comes in contact with medium-acid water, it  undergoes graphitization. Though the mechanism through which graphite grows in nodular cast iron is still being studied.

Some techniques, like Raman spectroscopy and trasmission electron microscopy can be very helpful to clarify this.

Nowadays we often hear a lot about photovoltaics: choosing the best material for semi-conductors might be very challenging.

One of the most innovative methods to achieve this is based on synchrotron radiation, a powerful method which can detect the optic characteristics of the material and show us all the metallic impurities.

All of these techniques are actually related to physics.

Once a professor told us that physics is the mother of all the scientific disciplines because it allows people to discover the secrets of universe.

After this poetic statement he immediately clarified: ”Well, physics might allow you to discover the secrets of universe only if you are smart. So please guys, don’t study physics. I am telling you this just because i love you all.” 

 

Last week i had the opportunity to visit CERN with my colleagues and i couldn’t help remembering about his words. Sometimes the ones who love you can make you suffer, indeed.

 

The ATLAS  Experiment

However,CERN  is a reference point for all the people into science.

Several experiments are performed there, but in this article i will  focus only about one of them: ATLAS.

The name is an acronym for A toroidal LHC apparatus, where LHC stands for Large Hadron Collider. The definition “ toroidal” is due to the external layer made of 8 superconducting magnets which form a toroid.

 

What is the Large Hadron Collider?

The biggest particles accelerator in the world: 27 km!

The collider looks like a big ring made of superconductive magnets which stir the particles around the ring. Their energy is increased in some chambers called radiofrequency cavities, where particles are charged.

 

The whole experiment is driven by particles collisions.

How are these collisions created?

Inside the accelerator two particle beams travel very fast in opposite direction (almost light velocity) until they are brought to collide at four  different locations at the LHC:  the interaction points where the experiments are actually conducted.

The trajectory of these particles is controlled by a very strong magnetic field provided by the electromagnets.

These devices are built from some spires which guarantee the efficient conduction of electricity (no energy losses).

To keep the beams around the accelerator, several magnets are used to make the particles stay closer and to increase the possibility of collisions.

 

 

The standard model

 What is the objective of the ATLAS experiment?

The idea is to study the subatomic particles and to understand if there are other elementary particles besides the ones described by the standard model. The behaviour of quantum particles has always been characterized by uncertainty and this is one of the reasons why Albert Einstein and Niels Bohr never became great friends.

In one of his  famous letters Einstein wrote that God does not play dice, meaning that  he could not accept the idea that quantum  particles behave differently when observed.

Regards the standard model, there are two macrocategories: fermions and bosons.

Fermions are the so called  “blocks of matter” and can be classified into quarks and leptons. There are also different kind of quarks: a quark of type “up” and a quark of type “down” make  a proton, for instance.

Among the leptons we have for instance electrons, muons and the super quick neutrinos.

 

What about bosons?

They are the force carriers, the particles able to bind fermions.

According to the theory of supersymmetry, not yet  experimentally verified, every fermion has its own associated boson.

Now it is necessary to say a few words about antimatter.

According to the big bang theory, our universe is supposed to contain  an almost equal amount of matter and antimatter.

 

 

We only need a very little asymmetry between matter/anti-matter to be left with current amount of matter found in the universe.

The term antimatter refers to particles with the same mass but opposite electric charge compared to the matter.

We all have heard of electrons, right?

The anti matter version of the electron is the positron.

The transformations between matter and anti matter are spontaneous and occur several times before they decay.

The question is: why do we see much more matter rather than anti matter?

This might be explained by a mechanism which caused the majority of particles to decay as matter rather than anti matter.

And here the Large Hadron Collider comes, where collisions are created to study the different behaviour of the particles.

To do this, a big amount of energy is required as particles need to travel very close to light velocity. The collisions energy is quantified thanks to the use of  several calorimeters: some particles are able to penetrate all the layers of them while others just go through the first layer (electrons).  Indeed the  interaction energy can be recalculated through the combination of direction and energy of daughter products for which calometry contributes.

 

The Higgs Boson

The ATLAS experiment is so revolutionary because it allows us to discover about things completely abstract and theoretical.

According to the first mathematical theories developed in the sixties, bosons were presented as intermediate particles carrying electromagnetic forces, with no mass.

On the other hand some experiments showed that the weak nuclear force was carried by bosons with consistent mass: the W boson and the Z boson.

The weak nuclear force is one of the four fundamental forces together with gravity, electromagnetism and the strong force.

One of the scientists who contributed to this discovery is Carlo Rubbia, who won the Nobel prize in 1984.

 

This contradiction about the mass of bosons is explained by the presence of a field in the universe, able to attribute mass to some of these bosons.

The responsible of this is…the Higgs Boson!

All the people were so excited about its discovery in 2012 for a good reason: this particle theorized in 1964 is definitely the holy grail of science.

Do you want to know why?

The Higgs boson really likes interacting with other particles. When they interact with fermions, matter is created.

All the particles acquire mass through the Higgs field; the more a particle interacts with the bosons, the heavier it is.

According to the theory there are several  types of bosons: photons,  bosons W+, W- and Z, 8 different types of gluons and the Higgs boson.

At the moment we don’t know if this last model is correct, but further experiments with higher collisions energy might give us an answer.

 

The huge potential of the technology involved in the experiments at CERN  and the multidisciplinarity are really impressive: some gas detectors originally designed for high energy experiments can be used for radiotherapy, several softwares developed for data analysis can be very helpful in different fields (collSpotting, Controls Middleware just to name a few of them). There is also an experiment, called CLOUD ( Cosmics Leaving Outdoor Droplets ) which aims to find the correlation between cosmic rays and clouds formation, for instance.

 

When you are working on such abstract and complex topics, endurance and enthusiasm are fundamental to get what you look for. Besides the enormous scientific value, the research projects carried out at CERN definitely show how powerful passion for science is.

 

 

 

Giulia Ioselli

 

We  express our gratitude to Acquaint B.V.  for organizing the visit and to Jan De Boer for the very accurate explanations