proton collision

Three billiard balls scatter across the table after a strike: their trajectories depend only on the initial push. But in the world of atomic nuclei, things are more complex: particles sense each other on the fly, even if they are not bound together. For a long time, physicists could only measure pairwise interactions, while what happens when three meet remained behind the scenes.

Dark matter is the invisible scaffolding of the universe. It's there, we know from the motion of stars and galaxies, but what this scaffolding is made of remains unknown. One guess is ultra-light particles similar to axions. They barely interact with ordinary matter, yet occasionally they do get involved.

In the distant Cigar Galaxy, there is an unusual beacon. It doesn't shine in the usual sense: its rays are born in a scorching cloud around a black hole that is devouring matter from a companion star. Such objects are called ultraluminous X-ray sources. Their X-ray brilliance is so intense that it outshines entire galaxies. This cloud, the corona, is like a boiling cauldron.

The 21-kilometer ring near Protvino was once planned to accelerate protons. Today, the same tunnel could host a very different machine — a muon collider. The muon is a heavy cousin of the electron, and that's its strength. On a curve, an electron radiates like a searchlight, losing precious energy. A muon radiates a billion times less.

Ice, water, steam — phase transitions we all know. But what happens if you squeeze and heat an atomic nucleus itself? Theorists think protons and neutrons inside it 'melt,' releasing smaller building blocks — quarks and gluons.

Deep inside the detector at the Large Hadron Collider, protons collide, and for a fleeting moment something heavy is born. It instantly shatters into two Higgs bosons — particles that, like nesting dolls, each hide two pairs of b-quarks.

A firework bursts, and one point explodes into four sparks at once. That's how the Z boson, the particle that carries the weak force, behaves when it decays into four charged leptons (electrons or muons). The process is extremely rare: for every million Z bosons produced, only about five decay this way.

A clap of the hands compresses the air, and it flies outward — the simplest shock. In space, exploding stars play the role of hands: their shock waves sharply compress gas and trigger chaotic mixing — turbulence.

A stone falls into a pond — ripples spread across the water. If the stone doesn't fall but whizzes over the surface at tremendous speed, a straight wave runs along the water. When it hits a floating log, ripples spread out from the point of impact. That's roughly how gravity works in the new study.

A pot of boiling soup bubbles away, and you'd love to know how hot individual droplets are inside. But you can only dip your thermometer at the edge, where things are calmer. Laser fusion is a bit like that: a powerful laser pulse hits a target, creating a cloud of fast protons.

At the Large Hadron Collider, protons collide billions of times per second, and only once in a trillion collisions does a pair of Standard Model Higgs bosons (the particles responsible for the mass of everything) emerge. In the CMS experiment, physicists hunted for exactly such events.

Two tin nuclei collide at about two-thirds the speed of light. For an instant, a hot, dense cloud forms, and protons fly out in all directions. If you catch pairs of protons and measure how often they fly off in the same direction, you can work out the size of that cloud. This method is called femtoscopy: it works like a microscope for nuclear scales.

Fusion, the merging of a proton with a boron-11 nucleus, promises a near-perfect energy source: no dangerous neutron flux, just a stream of charged particles that can be directly converted into electric current. But there's a fundamental problem: the Coulomb barrier.

In the CMS detector at the Large Hadron Collider, protons accelerated to nearly the speed of light collided. Among billions of such collisions, physicists searched for a rare signature: the production of a single heavy particle that immediately decays into a W boson and a b quark.

In a distant galaxy, at a distance that light takes 11 billion years to cross, something flashed. The Einstein Probe X-ray telescope caught a brief, needle-prick-like burst: it lasted only a few dozen seconds.

In a giant particle accelerator, particles smash into each other, and sometimes after the collision only two photons, particles of light, remain. Physicists can predict how often this happens, but their calculations have long disagreed with what detectors see. Each refinement of the theory changed the answer, and there was no consensus.

When two particles fly at almost the same speed in the same direction, their signals in the detector merge, like two voices in unison. Telling a duet from a soloist is an art in itself.

From 2016 to 2018, at the Large Hadron Collider at CERN, protons collided at energies of 13 teraelectronvolts, as if two peas were accelerated to speeds where their impact spawns a whole swarm of new particles.

At the Large Hadron Collider, protons collide, and from the flash dozens of particles are born. Among them may be traces of rare processes — for example, the decay of a Standard Model Higgs boson into two W bosons. But these particles fly apart so quickly that their tracks merge into a single wide jet.

Near black holes and neutron stars, plasma churns like water in a boiling kettle. But this 'kettle' has no walls — only magnetic fields that twist and tear. At the tears, thin sheets form where magnetic field lines reconnect, giving particles a kick like a surfer catching a wave.

Cosmic rays are particles that arrive from deep space. When such a particle hits the atmosphere, it triggers a whole shower of new particles, like a billiard ball breaking a rack, sending balls scattering in all directions. To predict what such a shower will look like, we need to know how the primary particle interacts with the nuclei of air atoms.

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.

Light reflecting off the scorching disk around a black hole can reveal more about it than we ever thought. When the disk emits heat, some of that light bounces back onto the disk and scatters, acquiring an unusual energy distribution, as if a new component, resembling a power law, is added to the ordinary glow.

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.

A ring road around the Sun, where the traffic is not cars but clumps of matter. The diameter of this road is measured in light-years: it encircles our planetary system at its outer edge, in the Oort Cloud, where the star's weak gravity still holds sway.

In the first instants after the big bang, the universe was a quantum vacuum where pairs of particles and antiparticles, virtual "guests" from physical nothingness, spontaneously appeared and almost immediately annihilated.

In the kitchen, two flashlight beams pass through each other without noticing. Light barely interacts with light. But if you accelerate particles to enormous energies, two photons can collide and give birth to something new.

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.

When a W boson, the particle that carries the weak force, decays into a quark and an antiquark, these two fragments fly off in nearly the same direction at the collider's immense speeds.

A dark matter detector is like a super-sensitive microphone listening for silence. It picks up tiny heat jolts, phonons, that occur when a particle grazes a crystal. But instead of silence, the instruments have been hearing noise for years: a slew of weak signals below a few hundred electronvolts.

When two lead nuclei collide at tremendous speed, a cloud of scorching matter is born for an instant — denser and hotter than the center of the Sun. Through this cloud fly jets of particles: narrow, laser-like beams knocked out by the impact. The CMS detector captures their tracks and shows how the jets change as they fight through the hot 'fog'.

In an underground ring 27 kilometers in circumference, protons are accelerated to nearly the speed of light and smashed head-on. At the collision point, conditions briefly recreate those of the first trillionth of a second after the birth of the universe.

In 2017, protons at the Large Hadron Collider collided with an energy of 5.02 TeV. The CMS detector recorded these collisions, and among billions of events, physicists hunted for a rare occurrence: the production of a single top quark without its antiparticle.

In turbulent air, droplets don't fly in straight lines: they get tossed around like dust motes in a beam of light. Physicists have built a setup that tracks each droplet, which is about a tenth of the thickness of a human hair. A camera captures their motion, and a computer reconstructs their trajectories.

Every time deuterium and tritium fuse in a fusion reactor, a fast neutron flies out. It can turn one substance into another — for example, create valuable isotopes for medicine. Today such neutrons cost a fortune, because there are few experimental facilities and they rarely operate.

In collisions of heavy nuclei, a fireball of thousands of particles is born. Among them are pions and kaons, two kinds of light particles that look very much alike. To understand what happens in this fireball, physicists need to know exactly how many of each particle flew out.

At the Large Hadron Collider, protons are smashed into lead nuclei. At the moment of impact, hundreds of new particles are born, and some of them fly out in narrow beams — jets. Inside such a jet, like in a dense stream, protons and neutrons can stick together to form larger nuclei, for example a deuteron — the nucleus of heavy hydrogen.

Somewhere above our heads, every second, a proton accelerated to energies millions of times greater than those at the Large Hadron Collider slams into the atmosphere. It strikes an air molecule, and a cascade is born — a wide atmospheric shower of thousands of particles.

In the 2010s, physicists working at the Large Hadron Collider learned to create in the lab a substance that doesn't exist in the ordinary world.

In the ATLAS detector at the Large Hadron Collider, protons collide billions of times per second. From this stream, physicists fished out eight events in which the collision produced two Z particles and one photon.