Supported options for symmetry breaking

All gauge symmetries can also be broken. This is in general done by decomposing a complex scalar into its real components and a VEV:

S_i \to \frac{1}{\sqrt{2}}(v_i + \phi_i + i \sigma_i)

Assigning a VEV to a scalar is not restricted to colourless and neutral particles. Also models with spontaneous colour or charge breaking (CCB) can be studied with SARAH. Also explicit CP violation in the Higgs sector is possible. There are two possibilities to define that. Either a complex phase is added

S_i \to \frac{1}{\sqrt{2}} e^{i\eta}(v_i + \phi_i + i \sigma_i)

or a VEV for the CP odd component is defined

S_i \to \frac{1}{\sqrt{2}} (v^R_i + \phi_i + i (v^I_i + \sigma_i))

Both options are possible in SARAH, even if the first one might often be preferred. In the case of an extended gauge sector also additional gauge bosons are present. Depending on the quantum numbers of the states which get a VEV these gauge bosons might mix with the SM ones. Also this mixing is fully supported by SARAH. There is no restriction if the additional gauge bosons are ultra-light (dark photons) or much heavier (Z′, W′-bosons).

See also