Êtes-vous un étudiant de l'EPFL à la recherche d'un projet de semestre?
Travaillez avec nous sur des projets en science des données et en visualisation, et déployez votre projet sous forme d'application sur Graph Search.
Concept
Méson J/ψ
Résumé
The _J/psi (J/psi) meson ˈdʒeɪ_ˈsaɪ_ˈmiːzɒn is a subatomic particle, a flavor-neutral meson consisting of a charm quark and a charm antiquark. Mesons formed by a bound state of a charm quark and a charm anti-quark are generally known as "charmonium" or psions. The _J/Psi is the most common form of charmonium, due to its spin of 1 and its low rest mass. The _J/Psi has a rest mass of 3.0969GeV/c2, just above that of the _charmed eta (2.9836GeV/c2), and a mean lifetime of 7.2e-21s. This lifetime was about a thousand times longer than expected.
Its discovery was made independently by two research groups, one at the Stanford Linear Accelerator Center, headed by Burton Richter, and one at the Brookhaven National Laboratory, headed by Samuel Ting of MIT. They discovered they had actually found the same particle, and both announced their discoveries on 11 November 1974. The importance of this discovery is highlighted by the fact that the subsequent, rapid changes in high-energy physics at the time have become collectively known as the "November Revolution". Richter and Ting were awarded the 1976 Nobel Prize in Physics.
The background to the discovery of the _J/Psi was both theoretical and experimental. In the 1960s, the first quark models of elementary particle physics were proposed, which said that protons, neutrons, and all other baryons, and also all mesons, are made from fractionally charged particles, the "quarks", which come in six types or "flavors", called up, down, top, bottom, strange and charm. Despite the ability of quark models to bring order to the "elementary particle zoo", they were considered something like mathematical fiction at the time, a simple artifact of deeper physical reasons.
Starting in 1969, deep inelastic scattering experiments at SLAC revealed surprising experimental evidence for particles inside of protons. Whether these were quarks or something else was not known at first. Many experiments were needed to fully identify the properties of the sub-protonic components.
Source officielle
À propos de ce résultat
Cette page est générée automatiquement et peut contenir des informations qui ne sont pas correctes, complètes, à jour ou pertinentes par rapport à votre recherche. Il en va de même pour toutes les autres pages de ce site. Veillez à vérifier les informations auprès des sources officielles de l'EPFL.
Cours associés (4)
PHYS-471: Particle physics: the flavour frontiers
This course will present experimental aspects of flavour physics primarily in the quark sector but also in the lepton sector and their role in the development of the Standard Model of particle physics
PHYS-415: Particle physics I
Presentation of particle properties, their symmetries and interactions.
Introduction to quantum electrodynamics and to the Feynman rules.
PHYS-416: Particle physics II
Presentation of the electroweak and strong interaction theories that constitute the Standard Model of particle physics. The course also discusses the new theories proposed to solve the problems of the
Séances de cours associées (18)
Aperçu de la chromatodynamique quantique
Couvre la chromatodynamique quantique, y compris la constante de couplage en cours d'exécution et le confinement des quarks et des gluons.
Relaxation cosmologique: Portail d'Axion Ténébreux
Déplacez-vous dans la relaxation cosmologique à travers le portail de l'axe sombre et ses implications pour la compréhension de la nature.
Quarks et Mesons : Isospin et symétrie des saveurs
Couvre les antiquarks, mésons, isospin, opérateurs d'échelle, et la symétrie de saveur dans les quarks et mésons.
Publications associées (234)
Personnes associées (52)
Unités associées (12)
Concepts associés (13)
Quarkonium
In particle physics, quarkonium (from quark and -onium, pl. quarkonia) is a flavorless meson whose constituents are a heavy quark and its own antiquark, making it both a neutral particle and its own antiparticle. The name "quarkonium" is analogous to positronium, the bound state of electron and anti-electron. The particles are short-lived due to matter-antimatter annihilation. Vector meson Light quarks (up, down, and strange) are much less massive than the heavier quarks, and so the physical states actually seen in experiments (η, η′, and π0 mesons) are quantum mechanical mixtures of the light quark states.
Plasma quarks-gluons
Le plasma de quarks et de gluons, ou QGP (pour Quark-Gluon Plasma) est un état de la matière qui existe à des températures et/ou des densités extrêmement élevées. Cet état consiste en une « soupe » de quarks et de gluons (presque) libres. Elle diffère en cela des autres états de la matière, comme les solides, les liquides ou les gaz, dans lesquels les quarks et les gluons sont confinés dans les hadrons. Le était sans doute présent dans l'univers durant les microsecondes après le Big Bang.
QCD matter
Quark matter or QCD matter (quantum chromodynamic) refers to any of a number of hypothetical phases of matter whose degrees of freedom include quarks and gluons, of which the prominent example is quark-gluon plasma. Several series of conferences in 2019, 2020, and 2021 were devoted to this topic. Quarks are liberated into quark matter at extremely high temperatures and/or densities, and some of them are still only theoretical as they require conditions so extreme that they cannot be produced in any laboratory, especially not at equilibrium conditions.