Weinberg angle

The Weinberg angle or weak mixing angle is a parameter in the Weinberg–Salam theory of the electroweak interaction, part of the standard model of particle physics, and is usually denoted as θ_W. It is the angle by which spontaneous symmetry breaking rotates the original
W0
and B⁰vector boson plane, producing as a result the
Z0
boson, and the photon.

It also gives the relationship between the masses of the W and Z bosons (denoted as m_W and m_Z),

The angle can be expressed in terms of the ${\displaystyle SU(2)_{L}}$ and ${\displaystyle U(1)_{Y}}$ couplings (g and g', respectively),

...
Wikipedia