Particle physics allows us to know which are the constituents of matter and their interactions. Throughout the 20th century physicists and mathematicians especially develop a model that explains the observable universe and in particular matter and its interactions, this model is called the "standard model." Elementary particles of matter and their interactions were built after Big Bang and four known forces or interactions are strong interaction, the weak interaction, electromagnetism and gravity of course. The Standard Model does not describe the fourth interaction, gravitational interaction.
What are these particles and how they interact with each other?
In the world of subatomic particles that make up matter, we manipulate the smallest of nature energies (eV) and extremely short lengths, on the order of 10-15 to 10-17 meters, well below the waist an atom which is 10-10 meters, but it is known that an atom consists of 99.99% empty. The particles are not visible, but however they are detectable if we apply sufficient energy, of the order of giga electron volts (GeV). Energy and mass are two aspects of the same phenomenon, according to Einstein's famous equation (E = mc2), the mass can be converted into energy and vice versa. Because of this equivalence, mass and energy can be measured with the same unit. At the level of particle physics, it is the electron volt (eV). In the standard model the elementary particles of matter are 12 in number, the six quarks, the three electrons and equivalents three neutrinos. The symmetry laws also called invariance, introduced in physics before 1964 can only be validated if the elementary particles do not have inertial mass.
But if, as the photon, the particles have no mass, so they can travel at the speed of light and the Universe can not contain matter because is that radiation, particles can not associate themselves with nuclei. Here comes the Higgs mechanism that gives mass to elementary particles and thus preserves the physical laws of symmetry.
Particles acquire mass by interacting with the Higgs field that permeates all of space. As often happens in science there are many precursors to a theory and it is the same for the Higgs mechanism, the precursors are Philip Warren Anderson, Yoichiro Nambu, Julian Schwinger, Robert Brout, François Englert, but Peter Higgs which best describes the mechanism and especially the Higgs itself. The co-discoverer of the Higgs mechanism are Gerald Guralnik, Carl Richard Hagen, Thomas Walter Bannerman Kibble. This mechanism was taken over by Steven Weinberg, Abdus Salam and Sheldon Glashow to create the standard model.
NB: energies manipulated in the LHC, the total energy released is 14 TeV (14 x 1012 eV). However, if we convert this amount in joules, it is a very small amount of energy:
1 eV = 1.60217653 x10-19 J.
14 TeV = 22.4 x10-7 J.
In comparison, the energy released by the falling of a stone of 1 kg falling from a height of 1 m, is 9.8 joules, or 10 million times the energy manipulated by the LHC. But the LHC energy is concentrated on a small electron beam, which is considerable.
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Image: Simulation of particle collisions. The particles are not visible, but however they are detectable if we apply sufficient energy, of the order of giga electron volts (GeV). Energy and mass are two aspects of the same phenomenon, according to Einstein's famous equation (E = mc2), the mass can be converted into energy and vice versa. Due to this equivalence, mass and energy can be measured with the same unit. At the level of particle physics, it is the electron volt (eV).
The Higgs mechanism gives mass to all elementary particles, but nothing is said about the mass of the Higgs boson itself, we only know that it has a mass between 2 GeV and 1000 GeV which is extremely vague. A particle can be observed in a detector that energies greater or egual to its own mass. The Higgs boson has not been observed in the detector at LEP (Large Electron Positron collider ), because the power of the collider (114 GeV ) is not enough to bring up the Higgs. It was therefore necessary to replace the LEP by the LHC (Large Hadron Collider ), a much more powerful collider 7000 GeV and 7 TeV.
LEP was disbanded in autumn 2000 and it is with the LHC operational since 10 September 2008, the scientists hoped to find the Higgs boson.
On 4 July 2012 discovery was announced and 14 March 2013, CERN (European Council for Nuclear Research) issued a press release in which he stated that the new boson discovered "looks more and more" to a Higgs boson even if it is not yet certain whether the Higgs boson of the standard model.
We now know that the Higgs boson has a mass of 126 GeV as Atlas and CMS, two of the four main experiments (Atlas, CMS, Alice and LHCb) were observed regardless of the round protons and deduce this property of the Higgs boson.
A crossing of proton bunch is realized every 50 nanoseconds and turning for hours in 1400 packets of 2048 protons in each direction, scientists can get some interesting collisions at the collision point of 20 microns located in each experiment.
Among all collisions (50 per cross), most are not interesting because they involve too low energies. After several reinjection of packets, to compensate wear (protons destroyed by collisions), computers will sort the interesting events to offer analysis .
In 2011 and 2012, approximately 1015 collisions were produced by experience (experience is the term used to name collisions observatories that are particle detectors Atlas, CMS, Alice and LHCb). The crossing zone that allows collisions has a length of 7 cm and a diameter of 20 microns.
In 1993, the British minister of science William Waldegrave launches a challenge to have an explanation the simplest possible of the Higgs field and Higgs boson. It was David Miller (CERN), which won the challenge proposing the following scenario:
At a meeting of physicists, guests fill the whole room uniformly, as the Higgs field fills all space. David Miller image represents the concept of quantum vacuum is not empty but where power fluctuations occur, the particles can interact with virtual real particles.
This is whereas in the room goes Einstein which symbolizes a free elementary particle of its movements, its inertial mass is zero.
As it advances in the room (quantum vacuum), people (virtual particles) cluster around him and it is difficult to grow, it acquires an inertial mass. We have then image of the vacuum which condenses around a particle.
The Higgs mechanism is precisely the vacuum condensation around a particle which interacts with the Higgs field, which gives it a mass.
Suppose this is not Einstein enters the room but a rumor spread that one (an energy of 126 GeV), then physicists will still cluster around the rumor to hear. This mass of people carrying the rumor represents the Higgs boson which acquires a mass (126 GeV).
Setting the BD scenario, CERN.
Image: Higgs boson, the enlarged image.
Image: Higgs fields.
Image: masse of the particle.
Both types of particles of nature are fermions and bosons. The matter that makes up the objects around us is made of fermions. Fermions are particles of spin 1/2 full, say asocial, in other words they refuse to reduce their living space, this is why the matter is not compressible and that we can walk on the floor. By cons the bosons are particles with integer spin that these are social. They like to mix as the light mixes with the light it is composed of photons, which are bosons.
The Standard Model describes with success, three of the four fundamental interactions: the strong interaction, the weak interaction and electromagnetic interaction. The table of particles contains 12 particles elementary (fermions) classified into three generations of matter, the matter around us is part of the first generation. The 12 elementary particles of matter are six quarks (up, charm, top, Down, Strange, Bottom) 3 electrons (electron, muon, tau) and three neutrinos (e, muon, tau). Four of these elementary particles would suffice in principle to build the world around us: the up and down quarks, the electron and the electron neutrino. Others are unstable and decay to reach these four particles. Bosons are the messengers that transmit information of different interactions (forces). The photon is the mediator particle of the electromagnetic interaction.
The gluon is the messenger of the strong nuclear interaction by structuring the matter. They confine the quarks together by binding strongly. The Z0 boson is one of the gauge bosons of the weak interaction, is the carrier particle of the weak interaction, the other being the boson W ± which presents in two opposite electric charges states.
NB: Most of the phenomena around us is due to the electromagnetic interaction, the mediator of the electromagnetic force is the photon. The photon is visible light, radio waves, ultraviolet rays, X-rays, gamma rays that fill our everyday environment. Photons are elementary energy "packets" or quanta of electromagnetic radiation, which are exchanged during the absorption or emission of light by matter.
Image: Table of elementary particles of the Standard Model Class fermions, the 12 constituents of matter (electron, muon, neutrino and quarks) and vector bosons of the interactions (forces). Vector bosons are also particles that carry the fundamental interactions. The generation of the particles II and III have the same properties as the generation of particles I but much heavier. Initially, to the period of Big Bang, all these particles coexisted but heavy particles are disintegrated into light particles. We do not find in nature, heavy particle of the generation II and III, only colliders are able to generate temporarily. At this table are missing antiparticles disappeared in favor of particles, each particle has its antiparticle. The Standard Model does not describe the gravitational interaction.
Credit image MissMJ Wikimedia Commons.
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Image: The particle sizes of material. The photon is formed of 2 quarks u, and 1 quark d, the proton charge is therefore +2/3 + 2/3 -1/3 it is +1, while the neutron is formed of 2 quarks d and 1 quark u, the charge of the neutron is therefore -1/3 -1/3 +2/3 it is 0. the electromagnetic force binds electrons to the nucleus. It allows the atoms forming molecules. This force is felt by the quarks and charged leptons, it is carried by photons.NB: Relative power (approximate) of the interactions. If the strong force is equal to 1, then the electromagnetic force is 10-2, i.e. 100 times lower, the weak force is 10-5, 10 000 times smaller and the force of gravity is 10-40, i.e. insignificant.