On the renormalization of operator products: the scalar gluonic case

In this paper we study the renormalization of the product of two operators $O_1=-\frac{1}{4} G^{\mu \nu}G_{\mu \nu}$ in QCD. An insertion of two such operators $O_1(x)O_1(0)$ into a Greens function produces divergent contact terms for $x\rightarrow 0$. In the course of the computation of the operator product expansion (OPE) of the correlator of two such operators $i\int\!\mathrm{d}^4x\,e^{iqx} T\{\,O_1(x)O_1(0)\}$ to three-loop order we discovered that divergent contact terms remain not only in the leading Wilson coefficient $C_0$, which is just the VEV of the correlator, but also in the Wilson coefficient $C_1$ in front of $O_1$. As this correlator plays an important role for example in QCD sum rules a full understanding of its renormalization is desireable. This work explains how the divergences encountered in higher orders of an OPE of this correlator should be absorbed in counterterms and derives an additive renormalization constant for $C_1$ from first principles and to all orders in perturnbation theory. The method to derive the renormalization of this operator product is an extension of the ideas of a paper by Spiridonov and can be generalized to other cases.Comment: v2: this is the version accepted by JHEP; more detailed discussion of phenomenological application

Vacuum stability in the SM and the three-loop \beta-function for the Higgs self-interaction

In this article the stability of the Standard Model (SM) vacuum in the presence of radiative corrections and for a Higgs boson with a mass in the vicinity of 125 GeV is discussed. The central piece in this discussion will be the Higgs self-interaction $\lambda$ and its evolution with the energy scale of a given physical process. This is described by the $\beta$-function to which we recently computed analytically the dominant three-loop contributions. These are mainly the QCD and top-Yukawa corrections as well as the contributions from the Higgs self-interaction itself. We will see that for a Higgs boson with a mass of about 125 GeV the question whether the SM vacuum is stable and therefore whether the SM could be valid up to Planck scale cannot be answered with certainty due to large experimental uncertainties, mainly in the top quark mass.Comment: Extended version of a talk given at the ISSP 2012 in Erice, 23 June - 2 July 2012, part of the proceedings for this school; v2: references added; v3: references added; v4: references added, improved Fig. 1; v5: final version as submitted for publication, new Fig.

Top-Yukawa effects on the β\beta-function of the strong coupling in the SM at four-loop level

We present analytical results for the QCD $\beta$-function extended to the gaugeless limit of the unbroken phase of the Standard Model at four-loop level. Apart from the strong coupling itself we include the top-Yukawa contribution and the Higgs self-coupling. We observe a non-naive $\gamma_5$ contribution at order $y_t^4 g_s^4$, a feature not encountered in lower loop orders.Comment: v2: more sophisticated treatment and more detailed description of the non-naive \gamma_5 contribution; Ref. added. v3: this the version published in JHEP; references [49,50] fixed; v4: changed statement on p.8: a different gamma_5 treatment only leads to a factor 3, not a factor 6 in the non-naive part compared to the prescription used in this paper. Note added on recent developments (p. 12