Longitudinal polarization refers to the orientation of the electric and magnetic fields of a photon as it propagates through space. In the Feynman photon propagator, it describes the probability of a photon with a specific momentum and energy to travel from one point to another.
Transverse polarization describes the perpendicular orientation of the electric and magnetic fields of a photon, while longitudinal polarization describes the parallel orientation. In the Feynman photon propagator, transverse polarization dominates, but longitudinal polarization becomes important at high energies.
Longitudinal polarization plays a crucial role in the calculation of scattering amplitudes in Feynman diagrams. It can affect the overall strength and behavior of interactions between particles, particularly at high energies. Understanding and accurately representing longitudinal polarization is important for making precise predictions in particle physics.
The inclusion of longitudinal polarization in Feynman diagrams can lead to ultraviolet divergences, which can make quantum field theories non-renormalizable. This is because longitudinal polarization can contribute to the overall strength of interactions, making the theory less predictive. Thus, renormalization techniques must be applied to account for these divergences.
Yes, longitudinal polarization can be observed in various experiments, particularly in high-energy particle collisions. For example, the Large Hadron Collider (LHC) at CERN has observed evidence of longitudinal polarization in certain scattering processes. However, it can be challenging to directly measure longitudinal polarization, and other techniques such as indirect measurements and theoretical calculations are often used.