Sunday 02 February 2025
Scientists at CERN’s Large Hadron Collider (LHC) have been studying a unique type of collision, known as ultra-peripheral collisions (UPCs). In these events, the protons and ions accelerated by the LHC don’t interact via the strong nuclear force, but instead behave like sources of quasireal photons. This allows researchers to study the properties of particles in ways that wouldn’t be possible otherwise.
One area of interest is the production of vector mesons, such as J/ψ and ρ0 particles. These mesons are created when a photon from one nucleus interacts with a colourless object from another nucleus. By studying these interactions, scientists can learn more about nuclear shadowing, gluon saturation, and other phenomena.
The ALICE collaboration at the LHC has been collecting data on UPCs for several years, and recently published some exciting new results. One of the most significant is the measurement of exclusive four-pion photoproduction, which is a process where four pions are produced in a single event. This is the first time this process has been measured at the LHC.
The ALICE collaboration also studied the production of K+K- pairs, which is another important area of research. By analyzing the data, scientists can learn more about the properties of the strong nuclear force and how it behaves under different conditions.
In addition to these results, the ALICE collaboration has been exploring the use of machine learning techniques in UPCs. For example, autoencoders can be used to detect anomalies in the data, such as the presence of exotic particles like tetraquarks or pentaquarks.
The future of UPC research looks bright, with even more exciting results expected from the upcoming Run 3 and 4 data sets. The new detectors being installed will allow scientists to study previously inaccessible regions of rapidity and make more precise measurements.
One area where researchers are particularly excited is the potential for beyond-the-Standard-Model physics. By studying light-by-light scattering, for example, scientists may be able to detect evidence of axion-like particles or other exotic phenomena. Similarly, the measurement of the tau lepton’s anomalous magnetic moment could provide insights into new forces or interactions.
Overall, the study of ultra-peripheral collisions is a rich and active field, with many exciting results and prospects for future discoveries.
Cite this article: “Unveiling New Insights in Ultra-Peripheral Collisions at CERNs LHC”, The Science Archive, 2025.
Large Hadron Collider, Ultra-Peripheral Collisions, Quasireal Photons, Vector Mesons, J/Ψ, Ρ0, Nuclear Shadowing, Gluon Saturation, Machine Learning, Beyond-The-Standard-Model
Reference: Simone Ragoni, “Overview of the latest ALICE UPC and photonuclear results” (2024).
