Model-independent constraints on Delta F=2 operators and the scale of New Physics

TL;DR

This paper updates constraints on new physics contributions to flavor-changing processes, deriving bounds on operator coefficients and the scale of new physics, indicating that non-standard operators imply a higher new physics scale than minimal models.

Contribution

It provides the most recent bounds on Delta F=2 operators and translates these into lower bounds on the new physics scale, highlighting the difference between standard and non-standard operator constraints.

Findings

Non-standard operators are more tightly constrained than Standard Model operators.

The scale of new physics for non-standard operators is likely beyond LHC reach.

Updated bounds significantly restrict possible new physics models.

Abstract

We update the constraints on new-physics contributions to Delta F=2 processes from the generalized unitarity triangle analysis, including the most recent experimental developments. Based on these constraints, we derive upper bounds on the coefficients of the most general Delta F=2 effective Hamiltonian. These upper bounds can be translated into lower bounds on the scale of new physics that contributes to these low-energy effective interactions. We point out that, due to the enhancement in the renormalization group evolution and in the matrix elements, the coefficients of non-standard operators are much more constrained than the coefficient of the operator present in the Standard Model. Therefore, the scale of new physics in models that generate new Delta F=2 operators, such as next-to-minimal flavour violation, has to be much higher than the scale of minimal flavour violation, and it most probably lies beyond the reach of direct searches at the LHC.