Model-independent Bounds on the Standard Model Effective Theory from Flavour Physics

Abstract

Meson-antimeson mixing provides the most stringent constraints on baryon- and lepton-number conserving New Physics, probing scales higher than $10^5$ TeV. In the context of the effective theory of weak interactions, these constraints translate into severe bounds on the coefficients of $\hat{I}”F=2$ operators. Generalizing to the effective theory invariant under the Standard Model gauge group, valid above the electroweak scale, the bounds from $\hat{I}”F=2$ processes also affect $\hat{I}”F=1$ and even $\hat{I}”F=0$ operators, due to log-enhanced radiative corrections induced by Yukawa couplings. We systematically analyze the effect of the renormalization group evolution above the electroweak scale and provide for the first time the full set of constraints on all relevant dimension-six operators.

8 pages, 8 tables. Table of DF=2 bounds on weak Hamiltonian added. Revised version published in Physics Letters B