Nuclear physics theorists at the U.S. Department of Energy’s Brookhaven National Laboratory have conducted research that has shown that complex calculations run on supercomputers can accurately predict the distribution of electric charges in mesons. These particles are made of a quark and an antiquark, and understanding the intricacies of mesons and other particles made of quarks, collectively known as hadrons, is crucial in high-energy experiments at the future Electron-Ion Collider (EIC) at Brookhaven Lab. The predictions and measurements at the EIC will help scientists unravel how quarks and gluons generate the mass and structure of visible matter.
The ultimate goal of the EIC is to understand how the properties of hadrons, including familiar protons and neutrons, are derived from the distributions of the constituent quarks and gluons. By studying pions, protons, and other hadrons, scientists hope to gain insight into how atomic nuclei are held together by the nuclear strong force. The recent predictions published in Physical Review Letters match well with measurements from low-energy experiments at the Thomas Jefferson National Accelerator Facility, Brookhaven’s partner in constructing the EIC. These predictions will serve as a comparison when experiments at the EIC commence in the early 2030s.
The research goes beyond simply setting expectations for EIC measurements. The scientists employed their predictions and supplementary supercomputer calculations to validate factorization, a widely used method for deciphering particle properties. Factorization divides complex physical processes into two factors, enabling a better understanding of the inner workings of particles. Confirming factorization will result in more confident interpretations of experimental results at the EIC, leading to a deeper understanding of quark and gluon distributions in hadrons.
The EIC will use high-energy electrons to collide with protons or atomic nuclei, emitting virtual photons that provide information about the properties of the target hadron. By conducting these collisions, scientists aim to obtain precise measurements of various physical scattering processes. Factorization, a theoretical approach, will be crucial in transforming these measurements into detailed images of the building blocks within hadrons. The factorization technique breaks down experimental measurements, such as the distribution of electric charges in mesons, into two components, allowing for a more comprehensive analysis.
The calculations involved in determining the distribution of quarks and gluons within hadrons are notoriously difficult due to the strong interactions between these particles. The theory of quantum chromodynamics (QCD) governs these interactions, requiring powerful supercomputers to simulate the processes. In contrast, interactions between quarks, gluons, and virtual photons are less complex, facilitating pen-and-paper calculations. Scientists can utilize these calculations alongside experimental measurements to infer the distribution of quarks and gluons inside hadrons, providing vital insights into the subatomic world.
The successful reverse factorization calculations, where quark-antiquark distributions in mesons were determined using supercomputers, validate the factorization approach. By comparing the predictions derived from factorization with those from independent simulations, scientists have confirmed the effectiveness of this method for solving complex problems. This research has significant implications, as it allows for more accurate predictions and analyses of EIC observables, enabling scientists to investigate quark and gluon distributions in hadrons that cannot be calculated directly. The work was supported by the DOE Office of Science and conducted at various DOE Office of Science user facilities.
