cassions
Cassions are a class of hypothetical particles proposed in speculative extensions of the Standard Model to mediate a new fundamental interaction, sometimes described as a fifth force. The term is used for both vector (spin-1) and scalar (spin-0) variants, which couple weakly to ordinary matter and are characterized by their mass and the symmetry structure of the underlying theory.
In many models, cassions arise from new gauge symmetries or hidden sectors that communicate with the Standard
Experimentally, cassions have not been observed. Constraints come from precision tests of gravity and electromagnetism, beam-dump
Variants include multiple cassions with different masses. The concept overlaps with other dark-sector mediators such as
History and usage vary across literature; the term appears in speculative works since the early 2000s. As