PRISMA Colloquium

Understanding the confinement mechanism in gauge theories and the universality of effective string-like descriptions of gauge flux tubes remains a fundamental challenge in modern physics. We probe string modes of motion with dynamical matter in a digital quantum simulation of a (2+1) dimensional gauge theory using a superconducting quantum processor with up to 144 qubits, stretching the hardware capabilities with quantum-circuit depths comprising up to 192 two-qubit layers. We realize the Z_2-Higgs model (Z_2HM) through an optimized embedding into a heavy-hex superconducting qubit architecture, directly mapping matter and gauge fields to vertex and link superconducting qubits, respectively. Using the structure of local gauge symmetries, we implement a comprehensive suite of error suppression, mitigation, and correction strategies to enable real-time observation and manipulation of electric strings connecting dynamical charges. Our results resolve a dynamical hierarchy of longitudinal oscillations and transverse bending at the end points of the string, which are precursors to hadronization and rotational spectra of mesons. We further explore multi-string processes, observing the fragmentation and recombination of strings. The experimental design supports 300,000 measurement shots per circuit, totaling 600,000 shots per time step, enabling high-fidelity statistics. We employ extensive tensor network simulations using the basis update and Galerkin method to predict large-scale real-time dynamics and validate our error-aware protocols. This work establishes a milestone for probing non-perturbative gauge dynamics via superconducting quantum simulation and elucidates the real-time behavior of confining strings. Ref: CERN-TH-2025-111 [arXiv:2507.08088]

Long-lived particles (LLPs) have attracted considerable attention in the past few years, in particular because several new "far" detectors have been proposed at the LHC. In this talk, I will discuss heavy neutral leptons (a.k.a. right-handed neutrinos). Due to their connection to neutrino mass generation HNLs are well-motivated LLPs. After introducing minimal HNLs and studying prospects for discovery at the LHC, I will turn to HNLs in effective field theory (EFT). EFTs are well suited to study non-minimal extension of the SM in the absence of new resonances at the LHC. The effects of non-renormalizable operators on prospects for HNLs discovery will be presented in some detail.