Glossary

Accelerator
A machine in which beams of charged particles are accelerated to high energies. Electric fields are used to accelerate the particles whilst magnets steer and focus them. A collider is a special type of accelerator where counter-rotating beams are accelerated and interact at designated collision points. A synchrotron is an accelerator in which the magnetic field bending the orbits of the particles increases with the energy of the particles. This keeps the particles moving in a closed orbit.

Aitoff projection
Aitoff projection is a modified azimuthal map projection. Proposed by David A. Aitoff in 1889, it is the equatorial form of the azimuthal equidistant projection, but stretched into a 2:1 ellipse while halving the longitude from the central meridian.

ALICE (A Large Ion Collider Experiment)
One of the four major experiments that will use the LHC.

AMS-IX (Amsterdam Internet Exchange)
The main place in the Netherlands for Internet Service Providers to interconnect and exchange IP traffic with each other at a national or international level.

Annihilation
A process in which a particle meets its corresponding antiparticle and both disappear. The resulting energy appears in some other form: as a different particle and its antiparticle (and their energy), as many mesons, or as a single neutral boson such as a Z boson. The produced particles may be any combination allowed by conservation of energy and momentum.

ANTARES (Astronomy with a Neutrino Telescope and Abyss Environmental Research). Large area water Cherenkov detector in the deep Mediterranean Sea near Toulon, optimised for the detection of muons resulting from interactions of high-energy cosmic neutrinos.

Antimatter
Every kind of matter particle has a corresponding antiparticle. Charged antiparticles have the opposite electric charge as their matter counterparts. Although antiparticles are extremely rare in the Universe today, matter and antimatter are believed to have been created in equal amounts in the Big Bang.

Antiproton
The antiparticle of the proton.

ApPEC (Astroparticle Physics European Coordination)
Consortium of national funding agencies aiming to develop long-term strategies in the field of astroparticle physics research.

ASPERA
Sixth Framework Programme for coordination across European funding agencies for financing astroparticle physics.

ATLAS (A Toroidal LHC Apparatus)
One of the four major experiments that uses the LHC.

BaBar
BB detector at SLAC's B Factory. Named for the elephant in Laurent DeBrunhoff's children's books.

Beam
The particles in an accelerator are grouped together in a beam. Beams can contain billions of particles and are divided into discrete portions called bunches. Each bunch is typically several centimeters long and can be just a few µm in diameter.

B Factory
SLAC's electron-positron collider, built to produce B-mesons, started in 1999.

Big Bang
The name given to the explosive origin of the Universe.

BNL (Brookhaven National Laboratories)
Laboratory where the RHIC accelerator is located.

Boson
The general name for any particle with a spin of an integer number (0, 1 or 2...) of quantum units of angular momentum (named for Indian physicist S.N. Bose). The carrier particles of all interactions are bosons. Mesons are also bosons.

Calorimeter
An instrument for measuring the amount of energy carried by a particle.

Cherenkov radiation
Light emitted by fast-moving charged particles traversing a dense transparent medium faster than the speed of light in that medium.

CHORUS (CERN Hybrid Oscillation Research Apparatus)
Experiment at CERN.

CLIC (Compact Linear Collider)
A site-independent feasibility study aiming at the development of a realistic technology at an affordable cost for an electron-positron linear collider for physics at multi-TeV energies.

Collider
See Accelerator.

Cosmic ray
A high-energy particle that strikes the Earth's atmosphere from space, producing many secondary particles, also called cosmic rays.

CP violation
A subtle effect observed in the decays of certain particles that betrays nature's preference for matter over antimatter.

CWI
Dutch Centre for Mathematics and Computer Science, Amsterdam

DØ (named for location on the Tevatron Ring)
Collider detector, studies proton-antiproton collisions at Fermilab's Tevatron.

Dark matter
Only 4% of the matter in the Universe is visible. The rest is known as dark matter and dark energy. Finding out what it consists of is a major question for modern science.

DELPHI
Experiment at LEP, CERN.

D-brane
In string theory, a higher dimensional membrane that provides an anchoring surface for strings.

Detector
A device used to measure properties of particles. Some detectors measure the tracks left behind by particles, others measure energy. The term 'detector' is also used to describe the huge composite devices made up of many smaller detector elements.

Dipole
A magnet with two poles, like the north and south poles of a horseshoe magnet. Dipoles are used in particle accelerators to keep the particles on a closed orbit.

EGI.eu (European Grid Infrastructure)
An EU-funded project led by CERN, now involving more than 90 institutions over 30 countries worldwide, to provide a seamless Grid infrastructure that is available to scientists 24 hours a day.

Elliptic flow
When two heavy nuclei collide in the centre of the STAR detector, the initial shape of the collision zone is usually an ellipse. Pressure in the liquid seeks to make the matter round, and so makes the liquid flow faster in the shorter direction. This elliptic flow can be measured in the speed and direction of the particles when they reach the detector, and the flow is largest when many particles are emitted from a given collision. The number of particles emitted depends on the intensity of that collision: how 'head-on' the collision between the two nuclei was.

End cap
Detector placed at each end of a barrel-shaped detector to provide the most complete coverage in detecting particles.

EUDET (European Detector R&D towards the International Linear Collider)
EU-funded R&D project for research on future ILC detectors.

EUnet
European UNIX network, Europe's largest Internet Service Provider.

eV (Electronvolt)
A unit of energy or mass used in particle physics. One eV is extremely small, and units of million electronvolts, MeV, or thousand million electronvolts, GeV, are more common in particle physics. The latest generation of particle accelerators reaches up to several million million electronvolts, TeV. One TeV is about the energy of motion of a flying mosquito.

Fermion
General name for a particle that is a matter constituent, characterized by spin in odd half integer quantum units (1/2, 3/2, 5/2...). Named for Italian physicist Enrico Fermi. Quarks, leptons and baryons are all fermions.

Forces
There are four fundamental forces in nature. Gravity is the most familiar to us, but it is the weakest. Electromagnetism is the force responsible for thunderstorms and carrying electricity into our homes. The two other forces, weak and strong, are connected to the atomic nucleus. The strong force binds the nucleus together, whereas the weak force causes some nuclei to break up. The weak force is important in the energy-generating processes of stars, including the Sun. Physicists would like to find a theory that can explain all these forces in one common framework. A big step forward was made in the late 1970s when the electroweak theory uniting the electromagnetic and weak forces was proposed. This was later confirmed in a Nobel prize-winning experiment at CERN.

FTE (Full Time Equivalent)
Unit of manpower

GeV
See Electronvolt.

Globus
Grid middleware toolkit development in the USA.

Gluon
See Particles.

Gravitational wave
The gravitational analog of an electromagnetic wave whereby gravitational radiation is emitted at the speed of light from any mass that undergoes rapid acceleration.

Grid
A service for sharing computer power and data storage capacity over the Internet.

Hadron
A subatomic particle that contains quarks, antiquarks, and gluons, and so experiences the strong force (see also Particles).

HERA
Hadron-Electron Ring Accelerator at DESY.

HERA-B
Fixed-target experiment at DESY, to investigate CP violation in the B-meson.

HERMES
DESY fixed-target experiment to explore spin.

High-Energy Physics
A branch of science studying the interactions of fundamental particles; called 'high-energy' because very powerful accelerators produce very fast, energetic particles probing deeply into other particles.

Higgs boson
A particle predicted by theory, linked to the mechanism by which physicists think particles acquire mass.

HiSPARC (High School Project on Astroparticle Cosmic Rays)
Cosmic-ray experiment with schools in the Netherlands.

ILC
International Linear Collider, now under study. A possible future electron-positron accelerator, proposed to be built as an international project.

Kaon
A meson containing a strange quark (or antiquark). Neutral kaons come in two kinds, long-lived and short-lived. The long-lived ones occasionally decay into two pions, a CP-violating process (see also Particles).

KM3NeT (Cubic Kilometre Neutrino Telescope)
Planned European deep-sea neutrino telescope with a volume of at least one cubic kilometre at the bottom of the Mediterranean Sea.

L3
Experiment at LEP, CERN.

LCAS (Local Centre Authorization System)
System to verify the GRID authorization.

LCG (LHC Computing Grid)
The mission of the LCG is to build and maintain a data-storage and analysis infrastructure for the entire high-energy physics community that will use the LHC.

LCMAPS (Local Credential MAPping Service) Provides all credentials necessary to access GRID services within a centre.

LEP
The Large Electron-Positron collider, which ran until 2000.

Lepton
A class of elementary particles that includes the electron. Leptons are particles of matter that do not feel the strong force (see also Particles).

LHC (Large Hadron Collider)
CERN's next big accelerator. LHCb (Large Hadron Collider beauty) One of the four major experiments that will use the LHC.

Linac
An abbreviation for linear accelerator.

LISA (Laser Interferometric Space Array)
ESA/NASA mission, the first space-based gravitational wave observatory; three spacecraft, orbiting around the Sun as a giant equilateral triangle 5 million km on a side.

LOFAR (Low Frequency Array)
First radio telescope of a new generation of astronomical facilities, mainly in the Netherlands.

Muon
A particle similar to the electron, but some 200 times more massive (see also Particles).

Muon chamber
A device that identifies muons, and together with a magnetic system creates a muon spectrometer to measure momenta.

Neutrino
Uncharged, weakly interacting lepton, most commonly produced in nuclear reactions such as those in the Sun. There are three known flavours of neutrino, corresponding to the three flavours of leptons. Recent experimental results indicate that all neutrinos have tiny masses (see also Particles).

NLO (Next-to-Leading Order)
Second-order calculations in perturbative QED and QCD.

Nucleon
The collective name for protons and neutrons.

PAO (Pierre Auger Observatory)
International experiment in Argentina to track down the origin of ultra-high energy cosmic rays.

Particles
There are two groups of elementary particles, quarks and leptons, with three families each. The quarks are named up and down, charm and strange, top and bottom (or beauty). The leptons are electron and electron neutrino, muon and muon neutrino, tau and tau neutrino. There are four fundamental forces, or interactions, between particles, which are carried by special particles called bosons. Electromagnetism is carried by the photon, the weak force by the charged W and neutral Z bosons, the strong force by the gluons; gravity is probably carried by the graviton, which has not yet been discovered. Hadrons are particles that feel the strong force. They include mesons, which are composite particles made up of a quark-antiquark pair, and baryons, which are particles containing three quarks. Pions and kaons are types of meson. Neutrons and protons (the constituents of ordinary matter) are baryons; neutrons contain one up and two down quarks; protons two up and one down quark.

Photon
See Particles.

Pion
See Particles.

Positron
The antiparticle of the electron.

Quantum electrodynamics (QED)
The theory of the electromagnetic interaction.

Quantum chromodynamics (QCD)
The theory for the strong interaction analogous to QED.

Quark
The basic building blocks of matter (see also Particles).

Quark-gluon plasma (QGP)
A new kind of plasma, in which protons and neutrons are believed to break up into their constituent parts. QGP is believed to have existed just after the Big Bang.

RASNIK (Red Alignment System Nikhef)
Optical alignment system where a pattern is projected by a lens on a CCD and deviations measured.

RELAXD
EU-funded development of the large area fast detector system using Medipix technology.

RHIC
Brookhaven's Relativistic Heavy Ion Collider; began operation in 2000. RHIC collides beams of gold ions to study what the Universe looked like in the first few moments after the Big Bang.

RICH (Ring Imaging CHerenkov)
A kind of particle detector that uses the light emitted by fast-moving charged particles as a means of identifying them.

SARA
Academic Computing Services of Amsterdam.

Scintillation
The flash of light emitted by an electron in an excited atom falling back to its ground state.

Solenoid
An electromagnet produced by current flowing through a single coil of wire. Many particle detectors are surrounded by a solenoidal magnet, since this produces a fairly uniform magnetic field within.

Spectrometer
In particle physics, a detector system containing a magnetic field to measure momenta of particles.

Spin
Intrinsic angular momentum of a particle.

Standard Model
A collection of theories that embodies all of our current understanding about the behaviour of fundamental particles.

STAR
Experiment at RHIC.

String Theory
A theory of elementary particles incorporating relativity and quantum mechanics in which the particles are viewed not as points but as extended objects. String theory is a possible framework for constructing unified theories that include both the microscopic forces and gravity (see also Forces).

Supersymmetry
A theory linking matter and forces.

SURFnet
Networking organisation in the Netherlands.

Synchrotron
See Accelerator.

TCP/IP (Transmission Control Protocol / Internet Protocol)
Suite of communications protocols to connect hosts on the Internet, invented in 1981.

TDR (Technical Design Report)
The blueprint for a (LHC) detector system.

Technology transfer
The promotion and dissemination of technologies, developed originally for scientific research, to third partied for socio-economic and cultural benefits.

TeV
See Electronvolt.

Tevatron
Fermilab's 2-TeV proton-antiproton accelerator.

Tier-1 First tier (category) in the LHC regional computing centers. Tier-0 is the facility at CERN collecting, reconstructing and storing the data.

Trigger An electronic system for spotting potentially interesting collisions in a particle detector and triggering the detector's read-out system to record the data resulting from the collision.

Valorisation French term for dissemination and exploitation of results.

Vertex detector A detector placed close to the collision point in a colliding beam experiment so that tracks coming from the decay of a short-lived particle produced in the collision can be accurately reconstructed and seen to emerge from a 'vertex' point that is different from the collision point.

VIRGO Detector near Pisa for gravitational waves: a Michelson laser interferometer made of two orthogonal arms, each 3 km long.

W boson A carrier particle of weak interactions; involved in all electric-charge-changing weak processes.

Z boson A carrier particle of weak interactions; involved in all weak processes that do not change flavour and charge.