Measuring the meson polarization modes from dilepton and kaon decays

Gubler, P. 

It has long been recognized that longitudinal and transverse modes of vector fields can behave differently in a hot and/or dense medium. This difference is caused by the presence of the static medium reference frame, which breaks Lorentz symmetry. While longitudinal and transverse spectral functions are degenerate for vector mesons at rest with respect to the medium, they can generally behave differently with increasing momentum. In this talk, I will discuss how the two polarization modes decay into dilepton and final states and how the corresponding angular dependences differ from each other. Furthermore, I will argue that the difference in the angular dependences can be used to disentangle the two polarization modes at the J-PARC E16 experiment.