Light (anti-) nuclei are a powerful tool both in collider physics and astrophysics. In searches for new and exotic physics, the expected small astrophysical backgrounds at low energies make these antinuclei ideal probes for, e.g., dark matter. At the same time, their composite structure and small binding energies imply that they can be used in collider experiments to probe the hadronization process and two-particle correlations. For the proper interpretation of such experimental studies, an improved theoretical understanding of (anti-) nuclei production in specific kinematic regions and detector setups is needed. In this work, we develop a coalescence framework for (anti-) deuteron production which accounts for both the emission volume and momentum correlations on an event-by-event basis: While momentum correlations can be provided by event generators, such as pythia, the emission volume has to be derived from semiclassical considerations. Moreover, this framework goes beyond the equal-time approximation, which has been often assumed in femtoscopy experiments and (anti-) nucleus production models until now in small interacting systems. Using pythia 8 as an event generator, we find that the equal-time approximation leads to an error of O(10%) in low-energy processes like ϒ decays, while the errors are negligible at CERN Large Hadron Collider energies. The framework introduced in this work paves the way for tuning event generators to (anti-) nuclei measurements.
Light (anti-) nuclei are a powerful tool both in collider physics and astrophysics. In searches for new and exotic physics, the expected small astrophysical backgrounds at low energies make these antinuclei ideal probes for, e.g., dark matter. At the same time, their composite structure and small binding energies imply that they can be used in collider experiments to probe the hadronization process and two-particle correlations. For the proper interpretation of such experimental studies, an improved theoretical understanding of (anti-) nuclei production in specific kinematic regions and detector setups is needed. In this work, we develop a coalescence framework for (anti-) deuteron production which accounts for both the emission volume and momentum correlations on an event-by-event basis: While momentum correlations can be provided by event generators, such as pythia, the emission volume has to be derived from semiclassical considerations. Moreover, this framework goes beyond the equal-time approximation, which has been often assumed in femtoscopy experiments and (anti-) nucleus production models until now in small interacting systems. Using pythia 8 as an event generator, we find that the equal-time approximation leads to an error of in low-energy processes like decays, while the errors are negligible at CERN Large Hadron Collider energies. The framework introduced in this work paves the way for tuning event generators to (anti-) nuclei measurements.