J. Wu

In the stream of cosmic rays, particles flying toward us from the depths of the Galaxy, titanium is rare. Its nuclei are almost indistinguishable from iron: both are heavy, and both leave similar tracks in detectors.

High above the Antarctic ice sheet, a balloon with a detector floated for twenty days. It caught tiny particles that had been traveling toward us for millions of years from distant stellar explosions. Now scientists have sorted through the catch and reported how much energy the protons and nuclei of different elements carried.

High above Antarctica, a balloon carried an instrument that caught electrons from space. These particles come from distant stellar explosions and other powerful events. The instrument measured their energy, like the force of an impact. And in one energy range, there were more impacts than calculations predicted.

In the stream of charged particles flying toward us from the depths of the Galaxy, iron turned out to be the odd one out. The ATIC-2 instrument, lifted on a balloon over Antarctica, compared how the fraction of nuclei from sulfur to chromium relative to iron changes with energy.

In 2016, the LHCb detector at the Large Hadron Collider recorded millions of proton-proton collisions. Among the debris of these collisions, neutral B mesons were born—particles that can spontaneously transform into their antiparticles and back.

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).

In a giant particle accelerator, where protons traveling at nearly the speed of light smash into a neon target, charmed baryons are born — particles that live for less than a billionth of a second.

Proton collisions at the Large Hadron Collider produce particles that live for less than a billionth of a second. One of them is the Bs meson, made of a strange quark and a bottom antiquark.

In the LHCb detector, like in a giant camera with billions of 'snapshots,' rare events are captured: how short-lived particles, B mesons, fall apart into lighter ones. One such decay, where a B meson turns into a kaon and a pair of muons, is particularly interesting. In it, as in a mirror, the difference between matter and antimatter may show up.

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.

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.

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.

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.

LIGO, Virgo, and KAGRA detectors act like giant microphones, listening in on gravitational waves — vibrations of space itself. The new GWTC-5.0 catalog recorded 161 black hole mergers, bringing the total count to 390 events.

At the Large Hadron Collider, protons are smashed together, and among the debris, a heavyweight particle, the lambda baryon, sometimes appears. It lives for a tiny fraction of a second before decaying into other particles.