The Overlooked Role of Projectile Coherence in the Few-Body Dynamics of Atomic Processes

The few-body problem (FBP) remains one of the fundamentally important and yet unsolved problems in physics. The essence of the FBP is that the Schrödinger equation is not analytically solvable for more than two mutually interacting particles even if the underlying force(s) are precisely known. As a result, theory has to resort to heavy modeling efforts to find solutions based on numeric approaches, which have to be tested by detailed experimental data. To this end we have performed numerous kinematically complete experiments over the last decade. Surprisingly, significant and qualitative discrepancies between measured and calculated data were found even for cases which previously were considered “easy” for theory. Only after a decade of vivid debates a possible explanation for this puzzling observation was offered. Experiments which we performed for projectiles of varying transverse coherence length suggested that the projectile coherence properties can have an important effect on the few-body dynamics and that these were not realistically treated by theory. This important point has been overlooked for decades of scattering theory. Since then mounting support for this explanation has been obtained from numerous follow-up experiments, which will be presented and analyzed in this talk.