In modern physics, antimatter is defined as matter composed of the antiparticles of the corresponding particles in "ordinary" matter, and can be thought of as matter with reversed charge, parity, and time, known as CPT reversal. Antimatter occurs in natural processes like cosmic ray collisions and some types of radioactive decay, but only a tiny fraction of these have successfully been bound together in experiments to form antiatoms. Minuscule numbers of antiparticles can be generated at particle accelerators; however, total artificial production has been only a few nanograms. No macroscopic amount of antimatter has ever been assembled due to the extreme cost and difficulty of production and handling.
Particle physics or high energy physics is the study of fundamental particles and forces that constitute matter and radiation. The fundamental particles in the universe are classified in the Standard Model as fermions and bosons. There are three generations of fermions, although ordinary matter is made only from the first fermion generation. The first generation consists of up and down quarks which form protons and neutrons, and electrons and electron neutrinos. The three fundamental interactions known to be mediated by bosons are electromagnetism, the weak interaction, and the strong interaction.
The European Organization for Nuclear Research, known as CERN, is an intergovernmental organization that operates the largest particle physics laboratory in the world. Established in 1954, it is based in a northwestern suburb of Geneva, on the France–Switzerland border. It comprises 23 member states. Israel, admitted in 2013, is the only non-European full member. CERN is an official United Nations General Assembly observer.
Antihydrogen is the antimatter counterpart of hydrogen. Whereas the common hydrogen atom is composed of an electron and proton, the antihydrogen atom is made up of a positron and antiproton. Scientists hope that studying antihydrogen may shed light on the question of why there is more matter than antimatter in the observable universe, known as the baryon asymmetry problem. Antihydrogen is produced artificially in particle accelerators.
The antiproton,
p
, is the antiparticle of the proton. Antiprotons are stable, but they are typically short-lived, since any collision with a proton will cause both particles to be annihilated in a burst of energy.
Antimatter-catalyzed nuclear pulse propulsion is a variation of nuclear pulse propulsion based upon the injection of antimatter into a mass of nuclear fuel to initiate a nuclear chain reaction for propulsion when the fuel does not normally have a critical mass.
ATHENA, also known as the AD-1 experiment, was an antimatter research project at the Antiproton Decelerator at CERN, Geneva. In August 2002, it was the first experiment to produce 50,000 low-energy antihydrogen atoms, as reported in Nature. In 2005, ATHENA was disbanded and many of the former members of the research team worked on the subsequent ALPHA experiment and AEgIS experiment.
Protonium, also known as antiprotonic hydrogen, is a type of exotic atom in which a proton and an antiproton orbit each other. Since protonium is a bound system of a particle and its corresponding antiparticle, it is an example of a type of exotic atom called an onium.
Antiprotonic helium is a three-body atom composed of an antiproton and an electron orbiting around a helium nucleus. It is thus made partly of matter, and partly of antimatter. The atom is electrically neutral, since both electrons and antiprotons each have a charge of −1, whereas helium nuclei have a charge of +2. It has the longest lifetime of any experimentally producible matter-antimatter bound state.
The ISOLDE Radioactive Ion Beam Facility, is an on-line isotope separator facility located at the heart of the CERN accelerator complex on the Franco-Swiss border. The name of the facility is an acronym for Isotope Separator On Line DEvice. Created in 1964, the ISOLDE facility started delivering radioactive ion beams to users in 1967. Originally located at the Synchro-Cyclotron (SC) accelerator, the facility has been upgraded several times most notably in 1992 when the whole facility was moved to be connected to CERN's ProtonSynchroton Booster (PSB). Entering its 6th decade of existence, ISOLDE is currently the longest-running facility in operation at CERN, a longevity due to a continuous development of the facility and its experiments that has kept ISOLDE at the forefront of science with radioactive ion beams. From the first pioneering isotope separation on-line (ISOL) beams to the latest technical advances allowing for the production of the most exotic species, ISOLDE benefits a wide range of physics communities with applications covering nuclear, atomic, molecular and solid-state physics, but also biophysics and astrophysics, as well as high-precision experiments looking for physics beyond the Standard Model. The facility is operated by the ISOLDE Collaboration, comprising CERN and sixteen (mostly) European countries. As of 2019, close to 1000 experimentalists around the world are coming to ISOLDE to perform typically 50 different experiments per year.
PAMELA was a cosmic ray research module attached to an Earth orbiting satellite. PAMELA was launched on 15 June 2006 and was the first satellite-based experiment dedicated to the detection of cosmic rays, with a particular focus on their antimatter component, in the form of positrons and antiprotons. Other objectives included long-term monitoring of the solar modulation of cosmic rays, measurements of energetic particles from the Sun, high-energy particles in Earth's magnetosphere and Jovian electrons. It was also hoped that it may detect evidence of dark matter annihilation. PAMELA operations were terminated in 2016, as were the operations of the host-satellite Resurs-DK1. The experiment was a recognized CERN experiment (RE2B).
The Antiproton Decelerator (AD) is a storage ring at the CERN laboratory near Geneva. It was built from the Antiproton Collector (AC) to be a successor to the Low Energy Antiproton Ring (LEAR) and started operation in the year 2000. Antiprotons are created by impinging a proton beam from the Proton Synchrotron on a metal target. The AD decelerates the resultant antiprotons to an energy of 5.3 MeV, which are then ejected to one of several connected experiments.
Atomic Spectroscopy and Collisions Using Slow Antiprotons (ASACUSA), AD-3, is an experiment at the Antiproton Decelerator (AD) at CERN. The experiment was proposed in 1997, started collecting data in 2002 by using the antiprotons beams from the AD, and will continue in future under the AD and ELENA decelerator facility.
The Antihydrogen Laser Physics Apparatus (ALPHA), also known as AD-5, is an experiment at the Antiproton Decelerator at CERN, designed to trap neutral antihydrogen in a magnetic trap, and conduct experiments on them. The ultimate goal of this experiment is to test CPT symmetry through comparison of the atomic spectra of hydrogen and antihydrogen. The ALPHA collaboration consists of some former members of the ATHENA collaboration or AD-1 experiment, as well as a number of new members.
AEgIS, AD-6, is an experiment at the Antiproton Decelerator facility at CERN. Its primary goal is to measure directly the effect of Earth's gravitational field on antihydrogen atoms with significant precision. Indirect bounds that assume the validity of, for example, the universality of free fall, the Weak Equivalence Principle or CPT symmetry also in the case of antimatter constrain an anomalous gravitational behavior to a level where only precision measurements can provide answers. Vice versa, antimatter experiments with sufficient precision are essential to validate these fundamental assumptions. AEgIS was originally proposed in 2007. Construction of the main apparatus was completed in 2012. Since 2014, two laser systems with tunable wavelengths and synchronized to the nanosecond for specific atomic excitation have been successfully commissioned.
BASE, AD-8, is a multinational collaboration at the Antiproton Decelerator facility at CERN, Geneva. The goal of the Japanese and German BASE collaboration are high-precision investigations of the fundamental properties of the antiproton, namely the charge-to-mass ratio and the magnetic moment.
Alexandre Obertelli is a French experimental nuclear physicist and Alexander von Humboldt Professor of Experimental Nuclear Structure Physics at the Institute of Nuclear Physics of the Technische Universität Darmstadt.
Jeffrey Scott Hangst is an experimental particle physicist at Aarhus University, Denmark, and founder and spokesperson of the ALPHA collaboration at the Antiproton Decelerator (AD) at CERN, Geneva. He was also one of the founding members and the Physics Coordinator of the ATHENA collaboration at the AD facility.
Extra Low ENergy Antiproton ring (ELENA) is a 30 m hexagonal storage ring that decelerates antiproton beams and delivers it to different AD experiments. It is situated inside the Antiproton Decelerator (AD) complex at CERN, Geneva. It is designed to further decelerate the antiproton beam coming from the Antiproton decelerator to an energy of 0.1 MeV for more precise measurements. The first beam circulated ELENA on 18 November 2016. The ring is expected to be fully operational by the end of the Long Shutdown 2 (LS2) in 2021.
