### Electroweak Precision Observables

The electroweak precision data (EWPD) measured at SLAC, LEP and Tevatron
provide a strong validation of the Standard Model (SM) description of the electroweak
interactions. With a precision in many cases of the order of one per mille, these
measurements have tested the SM to the level of radiative corrections, finding
good agreement between the data and the SM predictions. This sets strong
constraints on models with new physics modifying the electroweak sector. Moreover,
the recent discovery of the Higgs boson, with a mass consistent with the EWPD indirect
determination, implies that the global fit of the SM to EWPD is over constrained.

The standard set of electroweak precision observables has been implemented in the
$\texttt{HEPfit}$ code, including precision measurement at the $Z$-pole ($Z$ decay widths, left-right
and forward-backward asymmetries, the effective weak mixing angle), the $W$ mass and
width, the top and Higgs masses, the value of the strong coupling constant and the 5 flavor
contribution to the running of the electromagnetic constant ($\Delta \alpha^{(5)}_{had}$).
These can be used to test against the predictions of any model of interest. The following list
of models are implemented in the current version of $\texttt{HEPfit}$:

- The Standard Model of electroweak interactions.
- The SM plus the new physics in the form of contributions to the oblique parameters $S$, $T$, $U$.
- The SM plus new physics in the form of the so-called $\epsilon_{1,2,3,b}$ parameters.
- The SM plus new physics modifying the bottom quark neutral current couplings.
- The SM plus new physics modifying the couplings of the Higgs with the electroweak vector bosons.
- The dimension six Standard Model Effective Lagrangian.
- Two-Higgs-Doublet models.