The importance of dimension 8 SMEFT operators in concrete models

The Standard Model Effective Field Theory (SMEFT) is a generic way to parametrize the effects of heavy physics. Most SMEFT analyses focus on dimension 6 operators, which are often the leading correction to the Standard Model. However, some works have shown that dimension 8 operators can be important for some processes. Is expanding SMEFT to dimension 6 good enough? We attempt to address this question from the perspective of concrete models of new physics. We perform the tree-level matching from some UV models onto the SMEFT up to dimension 8 and examine the importance of the dimension 8 contributions in reproducing the predictions of the UV model.