2022 - SUMMER SEMESTER
ICTP-EAIF, University of Rwanda
University of Manchester
Towards a Non-Local S-Matrix Theory
In this talk we will discuss a non-local formulation of the S-matrix. To better understand the significance of the emerging quantum phenomena, we consider a solvable field-theoretic model. Present and future experiments may benefit from such non-local S-matrix construction, as the transition amplitude depends on the distance between the production and detection vertices. This solvable model enables accurate descriptions of detection regions that are either close to or far from the source. In close analogy with light diffraction in classical optics, we call these two regions near-field and far-field zones, or the Fresnel and Fraunhofer regions. We revisit the question whether mixed mediators produce an oscillating pattern if their detection occurs in the Fresnel region. We observe several novel features with respect to its angular dependence which have not been accounted before in the literature. In particular, we obtain a ``quantum obliquity factor'' that suppresses particle propagation in the backwards direction, thereby providing an explicit quantum field-theoretic description for its origin in diffractive optics.