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j psi particle

The J/ψ particle is a charm-anticharm meson whose decays are studied to probe physics beyond the Standard Model.
17 related articles

Description

The J/ψ particle is a meson — a particle made of a quark and an antiquark — specifically a charm quark bound to its antiparticle, the anticharm quark. It was discovered independently in 1974 by two teams, one led by Samuel Ting at Brookhaven and the other by Burton Richter at SLAC, in a landmark event that reshaped particle physics. The J/ψ is notable for its unusually long lifetime for a particle of its mass, which arises because its decay is suppressed by a quantum mechanical rule known as the OZI rule. This longevity makes it an excellent laboratory for studying the strong force and for searching for rare processes that could hint at new physics beyond the Standard Model.

History

The J/ψ was discovered in November 1974, independently by Samuel Ting's group at Brookhaven National Laboratory (who called it 'J') and Burton Richter's group at SLAC (who called it 'ψ'). The discovery was announced on November 11, 1974, and was so rapid and impactful that it became known as the 'November Revolution' in particle physics. Ting and Richter shared the 1976 Nobel Prize in Physics for the discovery.

How it works

The J/ψ is produced in high-energy particle collisions, such as electron-positron annihilation, where the energy converts into the charm-anticharm pair. Its decays are studied by detecting the particles it produces, such as muons, electrons, or photons. Because the J/ψ is relatively heavy (about 3.1 GeV/c²), it can decay into many different final states, and the relative rates of these decays — the branching fractions — are sensitive to the influence of new, undiscovered particles that might appear in quantum loops. By measuring these rates with high precision, physicists can look for deviations from Standard Model predictions, which would signal new physics.

In practice

The J/ψ is used as a calibration tool and a probe in particle physics experiments, such as those at CERN's LHC and at B-factories, to test the Standard Model and search for dark matter candidates through invisible decays.

Fun fact

The J/ψ's discovery was so unexpected that it was nicknamed the 'November Revolution' because it overturned the then-prevailing theory of quarks, which had predicted that charm quarks would be much heavier.

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Related articles · 17

HEP Experiment2026-08-211 minarXiv:2608.21082express
How a Heavyweight Particle Decays
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Charmonium Archaeology: A New Layer Excavated
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HEP Experiment2026-08-152 minarXiv:2608.15074express
Phase Shift in ψ(2S) Decay to Proton–Antiproton
When a ψ(2S) particle decays into a proton and an antiproton, two different mechanisms act simultaneously: the strong interaction, like glue holding quarks together, and the electromagnetic one, like light pushing charges apart. Their contributions add up with a certain phase shift.
HEP Experiment2026-04-291 minarXiv:2604.26784express
Rare decay spotted for the first time
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HEP Experiment2026-04-231 minarXiv:2604.21257express
A New Charmed Meson
In the LHCb detector, where protons collide, one unusual track was found among billions of decays. The particle, named $$D_{s1}$$(2933)^+, appears for a moment and immediately decays into other particles. Its lifetime is so short that it cannot be observed directly — only through its decay products can its existence be reconstructed.
HEP Experiment2026-04-141 minarXiv:2604.12524express
The Invisible Particle from the Quark World
Quarks are the tiny building blocks that make up protons and neutrons. Usually, they stick together in pairs: a particle and its mirror-image antiparticle. But sometimes quarks form more exotic combinations, which physicists call exotic states.
HEP Experiment2026-04-041 minarXiv:2604.03661express
Birth of Twin Particles in a Thick Target
Protons accelerated to enormous energies slam into a thick metal plate, like bullets into armor. Inside the metal, a J/ψ particle is born for an instant, which immediately decays into two muons — light relatives of the electron. These muons fly out of the target, and detectors catch their tracks. The scientists compared the number of caught muons with predictions from a computer model.
HEP Experiment2026-03-301 minarXiv:2603.28456express
Two-Charm Baryon Caught for the First Time
In proton collisions at the Large Hadron Collider, physicists have for the first time caught a particle with two charm quarks. It is called Ξcc+ (pronounced "ksi-ksi-plus") and resembles a bead with not one but two heavy nuclei.
HEP Experiment2026-03-241 minarXiv:2603.23081express
Photon Detective: How the J/psi Particle Decays
The J/psi particle lives for an instant and then decays into lighter particles, much like a snapped string scattering into pieces. Physicists from the BESIII collaboration caught over ten billion such decays to figure out exactly what 'pieces' are produced.
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Birth of Ghost Particles in Nuclear Collisions
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HEP Experiment2026-02-242 minarXiv:2602.20524express
Tiny Difference in Particle Decays
Two twins look identical, but one is left-handed and the other right-handed. In the world of elementary particles, there are similar pairs: Ξ- and its antiparticle Ξ+. They are born together in the decay of the J/ψ particle and, like entangled twins, maintain a connection even at a distance.
HEP Experiment2026-02-141 minarXiv:2602.13569express
Hunting Ghost Particles: What Belle II Saw
At Japan's KEK laboratory, electrons and their antimatter counterparts, positrons, collide inside the Belle II detector. In such collisions, new particles are born for a fleeting moment. Among them is J/ψ, a bound state of a charm quark and its antiquark.
HEP Experiment2026-02-101 minarXiv:2602.09652express
Invisible Particle: A New Decay of the Eta Meson
In the BEPCII accelerator, electrons and positrons collide, producing billions of particles. Among them is the J/ψ meson, which lives for less than a billionth of a second. Its decay sometimes yields an eta meson (ηc), an even shorter-lived clump of quarks.
HEP Experiment2026-02-042 minarXiv:2602.04276express
Antimatter Meets an Ordinary Proton
In a particle accelerator, the anti-lambda particle is a rare guest. It is born on the fly, lives for a tiny fraction of a second, and usually decays on its own. But sometimes it manages to collide with an ordinary proton, and then a whole shower of light particles is born: kaons, pions.
HEP Experiment2026-01-131 minarXiv:2601.08140express
Invisible Particle Decays
In the BESIII detector, particles put on a show: they collide, are born, and decay, leaving flashes of light. But sometimes an actor can leave the stage unnoticed — through a hidden door that cameras don't see. Physicists were looking for exactly such 'quiet' decays, when a particle turns into something invisible to the instruments.
High Energy2026-01-041 minarXiv:2601.01563express
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