QCD and strongly coupled gauge theories : challenges and perspectives

We highlight the progress, current status, and open challenges of QCD-driven physics, in theory and in experiment. We discuss how the strong interaction is intimately connected to a broad sweep of physical problems, in settings ranging from astrophysics and cosmology to strongly coupled, complex systems in particle and condensed-matter physics, as well as to searches for physics beyond the Standard Model. We also discuss how success in describing the strong interaction impacts other fields, and, in turn, how such subjects can impact studies of the strong interaction. In the course of the work we offer a perspective on the many research streams which flow into and out of QCD, as well as a vision for future developments.Peer reviewe

FASER and the Search for Light and Weakly Interacting Particles

For decades, the leading examples of new physics targets at particle colliders were particles with TeV-scale masses and O(1) couplings to the standard model. More recently, however, there is a growing and complementary interest in new particles that are much lighter and more weakly coupled. I review the motivations for this shift and the importance of renormalizable portals. I then present FASER, a proposed LHC experiment that is specifically designed to discover light and weakly interacting particles, including those that interact through renormalizable portal interactions