Probing squared four-fermion operators of SMEFT with meson-mixing

Abstract

The Standard Model Effective Field Theory (SMEFT) is a universal way of probing New Physics (NP) manifesting as new heavy particle interactions with the Standard Model (SM) degrees of freedom, that respect the SM gauged symmetries. Higher order terms in the NP interactions possibly lead to sizable effects, mandatory for meaningful phenomenological studies, such as contributions to neutral meson-mixing, which typically pushes the scale of NP to energy scales much beyond the reach of direct searches in colliders. I discuss for the first time the leading-order renormalization of double-insertions of dimension-6 four-fermion operators that change quark flavor by one unit (i.e., |Δ | = 1, = strange-, charm-, or bottom-flavor) by dimension-8 operators relevant for meson-mixing (i.e., |Δ | = 2) in SMEFT, and consider the phenomenological implications of contributions proportional to large Yukawas. Given the underlying interest of SMEFT to encode full-fledged models at low-energies, this work stresses the need of considering dimension-8 operators in phenomenological applications of dimension-6 operators of SMEFT.