Forest VirtualRealPhoton

Polarized Virtual Photons From Electrons

Virtual Photon Polarization

[math]\epsilon= \left [ 1 + 2 \left ( 1 + \frac{\nu^2}{Q^2}\right ) \tan^2\left( \frac{\theta_e^{\prime}}{2}\right)\right ][/math]

Longitudinal Photon Polarization

[math]\epsilon_L= \frac{Q^2}{\nu^2}\epsilon[/math]

Polarization Density Matrix

[math]Tr\left [ \gamma^\mu \gamma^\nu \right] = 4g^{\mu \nu} = 4 \begin{bmatrix} \frac{1}{2}(1+\epsilon) & 0 & \frac{1}{2}(1+\epsilon)\\ 0 & \frac{1}{2}(1-\epsilon) & 0 & 0\\ 0 & 0 & \epsilon_L\\ \end{bmatrix} [/math]

Reference: N. Dombey, Rev. Mod. Phys., 41, 236 (1969)

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