Particle Physics in a nutshell
Nature's inner working
Particle physics is CERN's main business. As much as biologists study living cells, chemists chemical compounds, particle physicists study the matter building blocks and the forces that hold them together. The microworld is a complex environment where rules that apply in the macroworld do not make sense and new phenomena and rules arise.
Particles are all around and inside us: the protons that we accelerate and study are exactly the same as those that compose the nuclei of the atoms you are made of. The processes and phenomena we study are the same that made it possible for our Universe to evolve. We collide particles and by doing so, we just reproduce what Nature does since ever. Indeed, natural particles coming from our Universe collide every second with the Earth atmosphere at energies much higher than those we reach in our powerful machines.
A selection of questions, not another textbook!
Today we are able to explain many of the phenomena we observe in Nature. That is why we are able to provide answers to some 'frequently asked questions'! Nevertheless, what you will find in this section is just a small - non exaustive - selection of the multitude of possible questions and topics. Writing long explanations of basic facts is not within the scope of this service. For this, we strongly invite you to make use of physics textbooks and on-line available encyclopedia.
Useful reminder: Powers of Ten
Useful reminder: Energy units in physics
Energy has many units in physics: joules, calories, and kilowatt hours are all units of energy used in different contexts. Only the 10-23 10–23 joule is an International System (SI) unit, but all of them are related by conversion factors. In particle physics, the unit that is most frequently used for energy is the electronvolt (eV) and its derivatives keV (103eV), MeV (106eV), GeV (109eV) and TeV (1012eV). The electronvolt is a convenient unit because, in absolute terms, the energies that particle physicists deal with are very small. If we take the LHC as an example, the total collision energy is 14 TeV, making it the most powerful particle accelerator in the world. Still, if we convert this into joules, we obtain:
14x1012x1.602x?10–19=22.4 x 10–7joules.
This is a very small amount of energy if compared, for example, to the energy of an object weighing 1kg and falling from a height of 1m, that is: 9.8joules=6.1x1019electronvolts.
The definition of the electronvolt comes from the simple insight that a single electron accelerated by a potential difference of 1volt will have a discreet amount of energy, E=qV joules, where q is the charge on the electron in coulombs and V is the potential difference in volts. Hence 1eV=(1.602x10–19C)
x (1 V)=1.602x10–19J.