Model-independent bounds on the standard model effective theory from flavour physics

Luca Silvestrini,Mauro Valli

doi:10.1016/j.physletb.2019.135062

Abstract

Meson-antimeson mixing provides the most stringent constraints on baryon- and lepton-number conserving New Physics, probing scales higher than 105 TeV. In the context of the effective theory of weak interactions, these constraints translate into severe bounds on the coefficients of ΔF=2 operators. Generalizing to the effective theory invariant under the Standard Model gauge group, valid above the electroweak scale, the bounds from ΔF=2 processes also affect ΔF=1 and even ΔF=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.

Highlights

Meson-antimeson mixing provides the most stringent constraints on baryon- and lepton-number conserving New Physics, probing scales higher than 105 TeV
Generalizing to the effective theory invariant under the Standard Model gauge group, valid above the electroweak scale, the bounds from F = 2 processes affect F = 1 and even F = 0 operators, due to log-enhanced radiative corrections induced by Yukawa couplings
Meson-antimeson mixing, a flavour changing neutral currents (FCNC) process with flavour quantum number F changed by two units ( F = 2), provides to date the most stringent constraints on baryon- and lepton-number conserving New Physics (NP), reaching an astonishing NP scale of O(105) TeV for strongly-interacting NP with arbitrary flavour structure [4,5,6]

Summary

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Model-independent bounds on the standard model effective theory from flavour physics. Meson-antimeson mixing, a FCNC process with flavour quantum number F changed by two units ( F = 2), provides to date the most stringent constraints on baryon- and lepton-number conserving NP, reaching an astonishing NP scale of O(105) TeV for strongly-interacting NP with arbitrary flavour structure [4,5,6]. If NP arises at scales much higher than the EW one, its leading effects in the EW and flavour sectors can be parameterized in terms of dimension-six local operators built of SM fields and invariant under the SM gauge group Those operators, together with the SM, form the so-called Standard Model effective field theory (SMEFT) [11,12]. A single bound is quoted for entries required to be real by Hermiticity

Led i jkl i jkl u

SM F

QQ i jkl dd i jkl

Le Q j jkl u