  It is not only conceivable but likely that the spectrum of physics beyond the
Standard Model (SM) is non-degenerate. The lightest non-SM particle may reside
close enough to the electroweak scale that it can be kinematically probed at
high-energy experiments and on account of this, it must be included as an
infrared (IR) degree of freedom (DOF) along with the SM ones. The rest of the
non-SM particles are heavy enough to be directly experimentally inaccessible
and can be integrated out. Now, to capture the effects of the complete theory,
one must take into account the higher dimensional operators constituted of the
SM DOFs and the minimal extension. This construction, BSMEFT, is in the same
spirit as SMEFT but now with extra IR DOFs. Constructing a BSMEFT is in general
the first step after establishing experimental evidence for a new particle. We
have investigated three different scenarios where the SM is extended by
additional (i) uncolored, (ii) colored particles, and (iii) abelian gauge
symmetries. For each such scenario, we have included the most-anticipated and
phenomenologically motivated models to demonstrate the concept of BSMEFT. In
this paper, we have provided the full EFT Lagrangian for each such model up to
mass dimension 6. We have also identified the $CP$, baryon ($B$), and lepton
($L$) number violating effective operators.
