Here are some common terms referenced in Particle Fever:

5 Sigma

Sigma, in a statistical sense, is the deviation from some norm and can represent a probability. When a 5-Sigma excess is announced (like evidence for the Higgs), the chance that the Higgs is not there and the data is due to a random fluctuation is 1 in 3.5 Million.


ATLAS (A Toroidal LHC ApparatuS) is one of the seven particle detector experiments (ALICE, ATLAS, CMS, TOTEM, LHCb, LHCf and MoEDAL) at the LHC, and one of two (with CMS) looking for the highest energy particles, such as the Higgs Boson, Supersymmetric partners, and Dark Matter.


All particles can be divided into two classes based on an internal property called spin. Matter particles, like electrons or quarks, are fermions. Force carrying particles are bosons.


The Compact Muon Solenoid (CMS) experiment is an LHC detector that lies on its French side and (like ATLAS) its goal is to investigate a wide range of physics, including the Higgs boson, extra dimensions, and particles that could make up dark matter.

Cosmological Constant

A parameter in Einstein’s theory of relativity which, when added, amounts to “vacuum energy”, or energy stored in space itself. It can cause the universe to expand at an accelerated rate — something which appears to be occurring today. The size of the cosmological constant is one of the biggest mysteries in theoretical physics.

Dark Matter

In astronomy and cosmology, dark matter is a type of matter hypothesized to account for a large part of the total mass in the universe. Evidence strongly suggests it isn’t ordinary matter – i.e., it is not made of atoms. A great hope for the LHC is that it will discover a new particle that could explain dark matter.


A hadron is a composite particle made of quarks held together by the strong force (in a similar way as atoms and molecules are held together by the electromagnetic force). Protons and neutrons are hadrons.

Higgs Boson

The Higgs boson or Higgs particle is an elementary particle initially theorized in 1964, and confirmed to exist on 14 March 2013. Its discovery completes the Standard Model, represents the first elementary particle seen without spin, and confirms the existence of the Higgs field.

Higgs Field

The Higgs field fills all of space and, according to the Standard Model theory, was ‘switched on’ moments after the Big Bang, which caused most elementary particles (quarks, the electron, weak force carriers) to acquire mass. The electron mass allows atoms to form and thus the Higgs field is responsible for all normal matter as we know it.


The Large Hadron Collider (LHC) is the world’s largest and most powerful particle accelerator. It first started up on 10 September 2008, and is the largest ring (27 km) in CERN’s accelerator complex. It consists of superconducting magnets to guide the particles and accelerating structures to boost the energy of the particles along the way. The machine is being upgraded currently and will operate at even higher energies in early 2015.


The multiverse is a theoretical description of spacetime in which our known universe is a small part of something much more vast in which the laws of nature might vary from place to place. The multiverse, while potentially a natural consequence of string theory and cosmic inflation, is not yet well-defined and by some is considered controversial.


Particles are, by definition, the smallest physical objects. Elementary particles are point-like, but can carry energy, mass, electric charge and other information or attributes. Study of fundamental particles is a key part of the study of the laws of nature.


Protons are positively charged subatomic particles that, along with neutrons, make up the nucleus of an atom. Protons are the particles that are accelerated and collided at the LHC.

Standard Model

The Standard Model is the current theory of elementary particles. It is literally a list of particles and their interactions which abide by the laws of quantum mechanics and relativity and describe nearly all known physical phenomena in our Universe at the microscopic level.


Supersymmetry is a special type of symmetry in physics which implies that there is a correspondence, at a fundamental level, between fermions and bosons (roughly particles which make up matter and particles responsible for forces). If supersymmetry were true, each Standard Model particle would have a corresponding ‘superpartner’, potentially discoverable at the LHC.