proton structure

Two nuclei with the same number of particles but different neutron skin shapes collide at speeds close to the speed of light. Ruthenium-96 and zirconium-96 are like twins, one with a slightly thicker coat. This difference changes how particles carry charge in the fireball of the 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.

The interiors of neutron stars are a realm of degenerate matter. Here, protons condense into a superconducting condensate, threaded by quantum vortices. Imagine tiny magnetic tops: each carries a quantum of magnetic flux and glides through the electron fluid.

An atomic nucleus is not just a ball of protons and neutrons. It has a shape, and that shape can change. The tin-116 nucleus was long considered almost perfectly spherical: it has 50 protons — a 'magic' number that usually gives a nucleus spherical symmetry. But a new ultra-precise measurement showed otherwise.

In accelerators like the Large Hadron Collider, heavy nuclei collide at enormous speeds. For an instant, quark-gluon plasma (QGP) is born — a state of matter where quarks and gluons float freely, just like in the first microseconds after the birth of the universe. This plasma is not just hot.

At accelerators, by smashing heavy nuclei, physicists briefly create a quark-gluon plasma — a state of matter where quarks and gluons are not confined inside particles but are free. For a long time, it was imagined as a gas, but experiments showed it's an almost perfect liquid.

Inside the proton, life is boiling. Quarks don't just sit there: they're glued together by carrier particles called gluons (from the word glue). Usually, this glue is spread evenly, like butter on a skillet. But when energies become enormous, gluons start clumping together. This is the gluon condensate — an ultra-dense state of the gluon field.

A drop of cream in a glass of milk. Shake it, and the fat doesn't spread evenly: it clumps into denser blobs that move differently from the rest of the liquid. Quarks inside mesons, tiny particles that live for mere fractions of a second, behave in much the same way. A meson consists of a quark and an antiquark, and they are rarely equals.

At first glance, the atomic nucleus is a cramped communal apartment where protons and neutrons (together called nucleons) live by strict rules. Each occupies its own orbit, like electrons in an atom, and on average everything looks orderly.

The atomic nucleus is not a solid ball but a dense swarm of tiny particles called quarks, glued together by a special glue (the strong force). In light nuclei, such as calcium, this swarm is simply arranged: the numbers of the two quark types, up and down, are almost equal, like the white and black keys in an octave.

If you try to break a proton apart and pull out a quark, you're in for a surprise. Ordinary forces, like the electric force, weaken as particles fly apart. Here, it's the opposite. The farther a quark gets from its neighbors, the harder it's pulled back.

Imagine a multi-story building where protons and neutrons live on each floor. The floors are energy levels, and usually there's a stairwell of a certain height between the sixth floor and the one above — the so-called gap. In the oxygen-20 nucleus, this gap acts as a barrier that particles find hard to cross.

A chemical reaction resembles passing through a turnstile: a crowd creates chaos and gets stuck, while an orderly line moves. In the quantum world, however, when the jostling subsides, the barrier can become ghostly — a particle passes through it as if the turnstile has vanished.

According to the Standard Model, the vacuum is not emptiness but an ocean of virtual ghost particles. An ultra-strong electromagnetic field, like a storm, yanks electron-positron pairs into reality.

At the Large Hadron Collider, not only nuclei but also individual protons collide. Even in such small systems, collective behavior resembling the flow of a liquid is observed. But the proton is a quantum object; its state is described by a wave function, not by temperature and pressure.

The proton looks like a solid ball, but inside it's a hive of activity: quarks exchange gluons — the particles that bind them together. Gluons pop in and out of existence, and their distribution within the proton is not just a curious detail but a key to predictions at the Large Hadron Collider.

The proton is not a solid ball but a seething cloud of quarks and gluons. Each particle carries its own bit of rotation, but if you add up all the bits, you don't get the full proton spin. Part of the rotation seems to hide in the cloud's slowest inhabitants: those carrying only a tiny share of the total motion.

Long before that, Fritz Zwicky predicted that a supernova explosion gives birth to a tiny neutron star. Years later, Jocelyn Bell Burnell caught its pulses, discovering pulsars.

Inside a fuel cell, protons must race through a solid material like commuters through turnstiles at rush hour. If the turnstiles are sparse and narrow, the current is weak. In the past, to find a material with good proton conductivity, chemists had to screen compounds almost blindly, one by one.

A rubber band is stretched, and suddenly snaps. In the atomic world, a similar picture emerges: the string binding particles can break. In a new study, physicists took a chain of Rydberg atoms and tracked how such a string breaks. Under weak tension, the string breaks completely, and the system splits into several independent pieces, as if a rubber band shattered into segments.

The proton is not a smooth ball but a tangle of smaller particles in constant motion. To peek inside, physicists fire electrons at protons and watch how they bounce off. The new machine, the Electron-Ion Collider, will do this with unprecedented accuracy. Scientists have run simulations to see what would happen if data were collected at different energies.

A magnesium oxide crystal is like a row of soldiers: atoms stand in neat lines, and an electron runs along them. But if the electron lingers, the nearest atoms shift slightly from their positions, like neighbors in a rank turning their heads. The electron finds itself in a dip made of displaced atoms and can no longer move freely.

Ten microseconds after the Big Bang, the Universe resembled a pot of boiling broth. Floating in it were quarks and gluons — the particles that would later assemble into protons and neutrons. As the broth cooled, at some point the quarks clumped together into lumps — the very protons and neutrons that make up all visible matter.

A bell doesn't ring with a single note — after being struck, it sounds with several harmonics at once. An atomic nucleus vibrates in much the same way: after a collision, it can oscillate, and these oscillations show up in the emitted gamma rays.