Researchers from the Institute of Modern Physics (IMP) of the Chinese Academy of Sciences (CAS), together with collaborators from the Instituto Tecnológico de Aeronáutica in Brazil and Iowa State University, have theoretically explored the influence mechanism of quark-gluon interactions on the parton distribution functions (PDFs) within hadrons, providing new insights into first-principles calculations of hadron structure.

Their findings are published as a letter in Physical Review D.

Hadrons are essential building blocks of the universe. These composite particles, which are composed of quarks and gluons, include protons, neutrons, pions, and others. Investigating the behavior of quarks and gluons within hadrons is crucial for unraveling the mysteries of the microscopic structure of matter.

As the number of particles in a physical system increases, its properties can change and different phase transitions (i.e., shifts into different phases of matter) can take place. Microscopic systems (i.e., containing only a few particles) and macroscopic ones (i.e., containing many particles) are thus typically very different, even if the types of particles they are made up of are the same.

Mesoscopic systems lie somewhere between microscopic and macroscopic systems, as they are small enough for individual particle fluctuations to impact their dynamics and yet large enough to support collective particle dynamics. Studying these middle-sized physical systems can yield interesting insight into how the fluctuations of individual particles can give rise to the collective particle behavior observed as a system grows.

Researchers at the University of California Berkeley and Columbia University recently introduced a new approach to precisely realize physical systems that are ideal for studying mesoscopic physics and the underpinnings of phase transitions. Their approach, outlined in a paper published in Nature Physics, relies on the use of atom tweezer arrays to control the number of atoms in a system and how they interact with light.

Researchers have demonstrated the slowing and subsequent reacceleration of a muon beam, increasing the potential of muon beams as a research tool.

About every second, the average human has a rare messenger from the edge of space passing through their body. Muons―similar to electrons but with 200 times the mass―are created naturally when cosmic ions strike the upper atmosphere, producing a shower of particles. Muons can also be created artificially, but these muon beams are very sparse compared to more conventional electron, proton, and ion beams. Over the past few decades, researchers have developed a way to make much denser beams [1, 2], but the difficulty of working with such beams has kept scientists from fulfilling their potential as a research tool. Now a team at the Japan Proton Accelerator Research Complex (J-PARC) has successfully demonstrated the capability to manipulate a dense muon beam, accelerating the muons in a radio-frequency device for the first time [3].