A cold-atom particle collider is proposed to simulate collider-relevant physics in a 1+1D U(1) lattice gauge theory with a tunable topological θ-term. The study demonstrates an experimentally feasible protocol to impart momenta to elementary and composite particles, enabling the exploration of rich phenomena such as oscillatory string dynamics, string inversion, and entropy production in the wake of particle collisions. The work numerically benchmarks collisions of moving wave packets for both elementary and composite particles, revealing insights into the dynamics of particle-antiparticle and meson-meson collisions. The results highlight the potential of cold-atom quantum simulators to investigate nonperturbative far-from-equilibrium physics in gauge theories, providing a pathway to understand collider-relevant phenomena in these platforms. The study also explores how collisions of composite particles reveal their internal structure and how the dynamics of particle-antiparticle collisions can be used to probe quantum criticality and phase transitions. The results show that the dynamics of particle-antiparticle collisions can be used to study quantum criticality and the behavior of the vacuum background, with the collision dynamics exhibiting distinct behavior depending on the final mass. The work sets the stage for future experiments in quantum simulators to explore the dynamics of particle collisions and the underlying physics of gauge theories.A cold-atom particle collider is proposed to simulate collider-relevant physics in a 1+1D U(1) lattice gauge theory with a tunable topological θ-term. The study demonstrates an experimentally feasible protocol to impart momenta to elementary and composite particles, enabling the exploration of rich phenomena such as oscillatory string dynamics, string inversion, and entropy production in the wake of particle collisions. The work numerically benchmarks collisions of moving wave packets for both elementary and composite particles, revealing insights into the dynamics of particle-antiparticle and meson-meson collisions. The results highlight the potential of cold-atom quantum simulators to investigate nonperturbative far-from-equilibrium physics in gauge theories, providing a pathway to understand collider-relevant phenomena in these platforms. The study also explores how collisions of composite particles reveal their internal structure and how the dynamics of particle-antiparticle collisions can be used to probe quantum criticality and phase transitions. The results show that the dynamics of particle-antiparticle collisions can be used to study quantum criticality and the behavior of the vacuum background, with the collision dynamics exhibiting distinct behavior depending on the final mass. The work sets the stage for future experiments in quantum simulators to explore the dynamics of particle collisions and the underlying physics of gauge theories.