besiii detector

Deep inside a mountain, where cosmic-ray muons are muffled by a thick layer of rock, stands a detector that catches not light but its absence. Positronium is a tiny atom in which an electron and its antiparticle, the positron, circle each other like a pair of dancers. Usually they come together and vanish in a flash of two or three gamma quanta.

Imagine a conveyor belt carrying 30 million parcels every second, and a controller who must instantly decide what is inside: a valuable shipment or junk. At the Large Hadron Collider, that conveyor belt is the trigger of the LHCb experiment, picking out rare particle decays among billions of collisions.

An archaeologist carefully brushes away layer after layer, and each new stratum at the charmonium dig is a rare decay captured by the detector. Charmonium — a bound state of a charm quark and its antiquark — lives for mere fractions of a second, yet it manages to tell us about the forces that hold quarks together.

The helium atom is like a tightly stretched string: every note it plays is strictly predicted by theory. But in recent years, precise measurements of one such "note"—the energy needed to strip an electron from an excited helium atom — have started to sound slightly higher than they should.

Blood vessel cells were seeded onto a transparent film just 700 nanometers thick — a hundred times thinner than a human hair. Flat electrodes are hidden beneath the film. They send a weak alternating current and listen as the resistance changes.

A regular radar is like a microphone in a buzzing crowd: individual sounds blend into mush. PiVoT works like a conductor who instantly recognizes each instrument in the tuning chaos. Instead of shuffling through hypotheses, the algorithm tightens a loop around the most likely targets — cars, cyclists, pedestrians.

Dark matter — the invisible architect of the universe, holding galaxies from flying apart. Thanks to the pioneering work of Fritz Zwicky and Vera Rubin we know: ordinary matter in the cosmos is just a negligible impurity. But what lies behind this dark matter?

3I/ATLAS burst into the Solar System like an uninvited guest, a gift of fate for hunters of extraterrestrial intelligence. This comet-like wanderer from the depths of the Galaxy flew close enough to be heard in all its details — unlike distant exoplanets.

A tiny coin circles a heavy bowling ball. The coin is a small black hole or a neutron star, and the ball is a supermassive black hole at the center of a galaxy.

Atomic nuclei are not always like billiard balls. Some are elongated, like cigars, others are flattened. But xenon-129 resembles a potato — a bumpy triaxial ellipsoid.

Physicists have proposed an experiment: a laser beam acts as a quantum detector and splits into two beam-ears. Each ear is directed through a tiny cloud of ultracold atoms — in this state, atoms merge into a single wave.

A coin landing on its edge is about as rare as a heavy B meson decaying into a light pion and an electron-positron pair. Over a decade of collider operation, only a handful of such events have accumulated, but physicists have finally managed to spot them. The decay probability is about 2.4×10⁻⁸.

A tiny glass bead hangs in a laser beam like a speck of dust in sunlight. Around it is a rarefied gas: atoms of krypton, xenon, and heavy molecules of sulfur hexafluoride. They collide with the bead, and each hit transfers a tiny impulse, like a pea thrown at a taut sheet makes it tremble. Impulse is a measure of motion: mass times velocity.

A cold cloud of atoms is like a swarm of fireflies drawn to one another. The attraction between atoms tries to pack them into a single dense ball. But quantum jitter, the unavoidable motion of particles, keeps the ball from collapsing. When the attraction is strong, the cloud breaks into separate clumps.

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.

Every second, billions of decays happen inside our bodies, and nobody notices. But physicists do: they smash particles in accelerators and watch what fragments they fly into. Hidden in those fragments is the answer to why we exist at all. Right after the Universe was born, there were equal amounts of particles and antiparticles, but today all we see around us is particles.

Imagine a balance scale with identical weights, yet one pan always tips lower. In the world of elementary particles, this imbalance is called CP violation: particles and their mirror twins (antiparticles) behave slightly differently.

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.

When heavy nuclei collide in accelerators, a multitude of particles is produced, and physicists want to understand how electric charge moves through this chaos. Two trains crash into each other: the passengers (quarks) scatter, but their luggage (charge) may end up far from the crash site.

In an accelerator near Beijing, electrons collide with positrons, and for an instant, particles are born that you wouldn't find in ordinary matter. One of them is lambda-c-plus: inside it sits a heavy charmed quark, like a stone in a slingshot. Now physicists have for the first time seen this particle break apart into a neutron, a positive pion, and an eta meson.

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.

At the Large Hadron Collider, protons collide at nearly the speed of light. Sometimes they don't smash apart but exchange photons — particles of light. These photons can produce a pair: one particle the detector sees, and another that flies off unnoticed.

Inside the proton and neutron, life is boiling: quarks exchange gluons, and for an instant pairs of particles appear and vanish. Some of them, the so-called scalar mesons, live for only 10⁻²³ seconds — less time than light needs to cross an atomic nucleus.

A tiny glass sphere floats in a laser beam like a speck of dust in sunlight. Inside it is radioactive lead, which decays from time to time. Each decay ejects charged particles, and the sphere loses or gains a tiny electric charge.

A power transistor made of silicon carbide operates under voltages thousands of times higher than what comes out of a wall outlet. If the field inside it becomes uneven, the device burns out. Previously, this field was invisible: it is too strong for ordinary sensors, and the device must remain under voltage.

When a fast proton slams into an atomic nucleus, new particles are born for an instant. One of them is the phi meson: a short-lived clump of matter that decays into an electron-positron pair. Catching this decay is like hearing the echo of a distant explosion: the blast itself is over, but its trace is still flying.

In a circular accelerator, electrons are accelerated to nearly the speed of light and smash into positrons: their antiparticles. At the collision point, a burst of pure energy briefly appears, from which new particles are born. The BESIII detector, like a high-speed camera, captures the tracks of these short-lived guests.

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.

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.

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.

In 2018, the Large Hadron Collider ran a special data-taking campaign: the CMS detector captured proton collisions at breakneck speed to collect ten billion particles containing a beauty quark.

In the dark, a tiny spark flashes. A gamma ray born inside a patient's body strikes a crystal and knocks out a shower of light. The detector's job is to figure out exactly where that happened. The more precise the answer, the sharper the image on the tomograph screen. The new detector resembles a honeycomb, but not a flat one — the cells narrow toward the bottom.

In a plasma accelerator, particles are accelerated like surfers riding a wave created in the plasma. If the leading bunch and the trailing bunch are not aligned, an instability arises that shakes the trailing bunch. It's as if a surfer on a wave starts wobbling from side to side: their trajectory gets messed up, and they might fall off the wave.

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.

Interstellar wanderers are rocks and icy chunks that have broken free from their home planetary systems and now drift through the Galaxy. The first such visitor, 'Oumuamua, zipped past the Sun in 2017, followed by Comet Borisov and the ATLAS object. Where do they come from?

In giant particle accelerators, particles fly at nearly the speed of light and smash head-on. But sometimes one beam is slightly denser than the other, like someone stepping onto a packed escalator the wrong way. Then collisions become uneven, and detectors start 'flickering,' throwing off measurements.

In the LHCb detector at the Large Hadron Collider, protons collide, and for a fleeting moment, particles that don't exist in ordinary matter are born. One of them is the neutral B meson. It lives for less than a billionth of a second and decays into two other particles: the narrow resonance J/ψ and the broader ρ(770).

At a particle accelerator in Beijing, electrons collide with positrons, and for a fleeting moment, a particle called eta-c is born. It lives for a tiny fraction of a second and then decays into other particles. One of the rarest paths is to split into two photons, particles of light. Until now, no one could say exactly how often this happens.

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.