Longitudinal polarization of a massive vector boson
= Longitudinal polarization of a massive vector boson
{title2=$\varepsilon_L^\mu$}
= Longitudinal gauge-boson polarization
{synonym}
A physical polarization of a massive spin-one <gauge boson> whose spatial polarization points along its spatial momentum. Together with two transverse polarizations it supplies the three physical spin states. In the <Higgs mechanism>, a broken-direction <Goldstone boson> supplies this extra state as the <gauge boson> acquires mass.