74 research outputs found
Accurate prediction of electroweak observables and impact on the Higgs mass bound
I discuss the importance of the O(g^4 m_t^2/\mw^2) corrections to the
effective electroweak angle and Mw in the indirect determination of the Higgs
mass. I emphasize the r\^ole of a very precise Mw measurement on the Mh
estimate.Comment: 9 pages, LaTex, uses appb.sty. Talk presented at the Zeuthen Workshop
on Elementary Particle Theory "Loops and Legs in Gauge Theories" Rheinsberg,
Germany, April 19-24, 199
The role of the top quark in the stability of the SM Higgs potential
I discuss the stability of the SM scalar potential in view of the discovery
of a Higgs boson with mass around 125 GeV. The role played by the top quark
mass in the choice between the full stability and the metastability conditions
is analyzed in detail. The present experimental value of the top mass do not
support the possibility that the SM potential is stable up to the Planck scale
but favor an electroweak vacuum sufficiently long-lived to be metastable.Comment: 7 pages, 6 figures. To appear on the Proceedings of LC13 Workshop:
exploring QCD from the infrared regime to heavy flavour scales at
B-factories, the LHC and a Linear Collider, 16-20 September 2013, ECT*, Villa
Tambosi, Villazzano (TN), Ital
Two-loop heavy top effects on the MZ-MW interdependence
The O(alpha^2 mt^2/mw^2) correction to the relation between G_\mu and the
vector boson masses is computed in the MSbar scheme, and the results are used
to investigate the magnitude of the effect on the theoretical prediction of mw
and sin^2\theta_\msbar(mz) from alpha, G_\mu, and mz.Comment: 11 pages, LaTeX, includes 1 LaTeX figure, uses equations.sty and
cite.sty, one minor comment and interpolation function for variable mtop
added, no change in the result
Current Algebra Approach to Heavy Top Effects in
The and corrections
to the partial decay width are computed
using the current algebra formulation of radiative corrections. This framework
allows one to easily enforce the relevant Ward identity that greatly simplifies
the calculations. As a result, the one-loop
contribution is computed through the investigation of only two convergent
diagrams. The computation of the QCD corrections to the one-loop term involves fewer diagrams than in the standard approach. In
particular, the number of infrared divergent contribution is reduced. The
calculation is performed in the dimensional regularization scheme and no term
more divergent than is found. Our result confirms the screening
of the one-loop top mass effect recently found by Fleischer {\em et al.}.Comment: 21 pages, 6 figures (not included) available upon request, LaTex,
DFPD 93/TH/0
Constraints on the trilinear Higgs self coupling from precision observables
We present the constraints on the trilinear Higgs self coupling that arise
from loop effects in the boson mass and the effective sine predictions. We
compute the contributions to these precision observables of two-loop diagrams
featuring an anomalous trilinear Higgs self coupling. We explicitly show that
the same anomalous contributions are found if the analysis of and \mbox{\sin^2 \theta^{{\rm lep}}_{{\rm eff}}} is
performed in a theory in which the scalar potential in the Standard Model
Lagrangian is modified by an (in)finite tower of terms
with the Higgs doublet. We find that the bounds on the trilinear Higgs
self coupling from precision observables are competitive with those coming from
Higgs pair production.Comment: 23 pages, 4 figures; V2: References added, version published on JHE
Probing the Higgs self coupling via single Higgs production at the LHC
We propose a method to determine the trilinear Higgs self coupling that is
alternative to the direct measurement of Higgs pair production total cross
sections and differential distributions. The method relies on the effects that
electroweak loops featuring an anomalous trilinear coupling would imprint on
single Higgs production at the LHC. We first calculate these contributions to
all the phenomenologically relevant Higgs production (, VBF, ,
, ) and decay (, , ,
) modes at the LHC and then estimate the sensitivity to the
trilinear coupling via a one-parameter fit to the single Higgs measurements at
the LHC 8 TeV. We find that the bounds on the self coupling are already
competitive with those from Higgs pair production and will be further improved
in the current and next LHC runs.Comment: 34 pages, 13 figures, 5 tables; V2: New appendix A added on the
comparison with the Effective Field Theory approach; V3: Journal versio
Higgs boson pair production at NLO in the POWHEG approach and the top quark mass uncertainties
We present a new Monte Carlo code for Higgs boson pair production at
next-to-leading order in the POWHEG-BOX Monte Carlo approach. The code is based
on analytic results for the two loop virtual corrections which include the full
top quark mass dependence. This feature allows to freely assign the value of
all input parameters, including the trilinear Higgs boson self coupling, as
well as to vary the renormalization scheme employed for the top quark mass. We
study the uncertainties due to the top-mass renormalization scheme allowing the
trilinear Higgs boson self coupling to vary around its Standard Model value
including parton shower effects. Results are presented for both inclusive and
differential observables.Comment: 21 pages, 7 figure
Precise calculation of MW, sin^2 theta_MSbar, and sin^2 theta_eff
The two-loop O(g^4 mt^2/mw^2) corrections are incorporated in the theoretical
calculation of MW, sin^2 theta_MSbar(MZ), and sin^2 theta_eff, as functions of
MH. The analysis is carried out in a previously proposed MSbar formulation and
two novel on-shell resummation schemes. It is found that the inclusion of the
new effects sharply decreases the scheme and residual scale dependence of the
calculations. QCD corrections are incorporated in two different approaches.
Comparison with the world average of sin^2 theta_eff leads to MH= 127 +143 -71
GeV and MW= 80.367 +/- 0.048 GeV, with small variations among the six
calculations.Comment: 10 pages, Latex, 3 table
Two-loop electroweak corrections to the Higgs-boson decay H -> gamma gamma
The complete set of two-loop electroweak corrections to the decay width of
the Higgs boson into two photons is presented. Two-loop contributions involving
weak bosons and the top quark are computed in terms of an expansion in the
Higgs external momentum. Adding these results to the previously known light
fermion contributions, we find that the total electroweak corrections for a
Higgs boson with 100 GeV <m_H < 150 GeV are moderate and negative, between -4%
< delta_EW < 0%. Combination with the QCD corrections, which are small and
positive, gives a total correction to the one-loop results of |
delta_{EW+QCD}|< 1.5 %.Comment: 15 page
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