Abstract
New physics not far above the TeV scale should leave a pattern of virtual effects in observables at lower energies. What do these effects tell us about the flavor structure of a UV theory? Within the framework of the Standard Model Effective Field Theory (SMEFT), we resolve the flavor structure of the Wilson coefficients in a combined analysis of top-quark and B-physics observables. We assume that the Yukawa couplings are the only sources of flavor symmetry breaking, a framework known as Minimal Flavor Violation. Our fits to LHC and b-factory measurements show that combining top and bottom observables is crucial to pin down possible sources of flavor breaking in a UV theory. This analysis includes the full analytic expansion of SMEFT coefficients in Minimal Flavor Violation and a detailed study of SMEFT effects in b → s flavor transitions.
Highlights
Effective Field Theory (SMEFT) below the TeV scale and parametrize BSM effects as a series of local operators [1, 2]
The key question is: what can we learn from data about the possible structure of UV physics? By resolving the parameter space of Standard Model Effective Field Theory (SMEFT) Wilson coefficients, we strive to pin down features of a UV theory that are in overall agreement with data
The top quark has played a crucial role in pinning down the flavor structure of the Standard Model: flavor-changing neutral currents among down quarks are driven by virtual effects of the top quark in loops; they have been studied in great detail in rare meson decays [12]
Summary
In theories where the mass scale Λ of BSM physics lies above the reach of current particle physics experiments, we can describe observable effects of such BSM effects by an effective quantum field theory with Standard Model particles as dynamical degrees of freedom. We use two kinds of effective theories: at energy scales above the weak scale μ = mZ, relevant for top and Higgs processes, we work with the Standard Model Effective Field Theory (SMEFT) [1]. We match the SMEFT onto the Weak Effective Theory (WET) [47, 51], which is the appropriate framework to describe new physics effects in flavor observables at low scales μ = mb. Where the sum is over all dimension-six operators with external quark fields. We do not include operators with leptons, assuming that new physics couples dominantly to quarks. And below in eqs. (2.2) and (2.3) non-hermitian operators are marked as ‡O
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