29 research outputs found
Three-loop \beta-functions for top-Yukawa and the Higgs self-interaction in the Standard Model
We analytically compute the dominant contributions to the \beta-functions for
the top-Yukawa coupling, the strong coupling and the Higgs self-coupling as
well as the anomalous dimensions of the scalar, gluon and quark fields in the
unbroken phase of the Standard Model at three-loop level. These are mainly the
QCD and top-Yukawa corrections. The contributions from the Higgs
self-interaction which are negligible for the running of the top-Yukawa and the
strong coupling but important for the running of the Higgs self-coupling are
also evaluated.Comment: 22 pages, 7 figures. Few extra citations are added; the plots are
improved. Results in computer readable form can be retrieved from
http://www-ttp.particle.uni-karlsruhe.de/Progdata/ttp12/ttp12-012
Higgs mass and vacuum stability in the Standard Model at NNLO
We present the first complete next-to-next-to-leading order analysis of the
Standard Model Higgs potential. We computed the two-loop QCD and Yukawa
corrections to the relation between the Higgs quartic coupling (lambda) and the
Higgs mass (Mh), reducing the theoretical uncertainty in the determination of
the critical value of Mh for vacuum stability to 1 GeV. While lambda at the
Planck scale is remarkably close to zero, absolute stability of the Higgs
potential is excluded at 98% C.L. for Mh < 126 GeV. Possible consequences of
the near vanishing of lambda at the Planck scale, including speculations about
the role of the Higgs field during inflation, are discussed.Comment: 35 pages, 8 figures. Final published version, misprints fixed,
figures update
Precise prediction for the light MSSM Higgs-boson mass combining effective field theory and fixed-order calculations
In the Minimal Supersymmetric Standard Model heavy superparticles introduce large logarithms in the calculation of the lightest -even Higgs-boson mass. These logarithmic contributions can be resummed using effective field theory techniques. For light superparticles, however, fixed-order calculations are expected to be more accurate. To gain a precise prediction also for intermediate mass scales, the two approaches have to be combined. Here, we report on an improvement of this method in various steps: the inclusion of electroweak contributions, of separate electroweakino and gluino thresholds, as well as resummation at the NNLL level. These improvements can lead to significant numerical effects. In most cases, the lightest -even Higgs-boson mass is shifted downwards by about 1 GeV. This is mainly caused by higher-order corrections to the top-quark mass. We also describe the implementation of the new contributions in the code FeynHiggs
Specific heat of 2D interacting Majorana fermions from holography
Majorana fermions are a fascinating medium for discovering new phases of matter. However, the standard analytical tools are very limited in probing the non-perturbative aspects of interacting Majoranas in more than one dimensions. Here, we employ the holographic correspondence to determine the specific heat of a two-dimensional interacting gapless Majorana system. To perform our analysis we first describe the interactions in terms of a pseudo-scalar torsion field. We then allow fluctuations in the background curvature thus identifying our model with a (2 + 1)-dimensional Anti-de Sitter (AdS) geometry with torsion. By employing the AdS/CFT correspondence, we show that the interacting model is dual to a (1 + 1)-dimensional conformal field theory (CFT) with central charge that depends on the interaction coupling. This non-perturbative result enables us to determine the effect interactions have in the specific heat of the system at the zero temperature limit