3 research outputs found
First Glimpses at Higgs' face
The 8 TeV LHC Higgs search data just released indicates the existence of a
scalar resonance with mass ~ 125 GeV. We examine the implications of the data
reported by ATLAS, CMS and the Tevatron collaborations on understanding the
properties of this scalar by performing joint fits on its couplings to other
Standard Model particles. We discuss and characterize to what degree this
resonance has the properties of the Standard Model (SM) Higgs, and consider
what implications can be extracted for New Physics in a (mostly)
model-independent fashion. We find that, if the Higgs couplings to fermions and
weak vector bosons are allowed to differ from their standard values, the SM is
~ 2 sigma from the best fit point to current data. Fitting to a possible
invisible decay branching ratio, we find BR_{inv} = 0.05\pm 0.32\ (95% C.L.) We
also discuss and develop some ways of using the data in order to bound or rule
out models which modify significantly the properties of this scalar resonance
and apply these techniques to the global current data set.Comment: 26 pages, 7 figures, v2 post ICHEP data updat
Vacuum Instabilities with a Wrong-Sign Higgs-Gluon-Gluon Amplitude
The recently discovered 125 GeV boson appears very similar to a Standard
Model Higgs, but with data favoring an enhanced h to gamma gamma rate. A number
of groups have found that fits would allow (or, less so after the latest
updates, prefer) that the h-t-tbar coupling have the opposite sign. This can be
given meaning in the context of an electroweak chiral Lagrangian, but it might
also be interpreted to mean that a new colored and charged particle runs in
loops and produces the opposite-sign hGG amplitude to that generated by
integrating out the top, as well as a contribution reinforcing the W-loop
contribution to hFF. In order to not suppress the rate of h to WW and h to ZZ,
which appear to be approximately Standard Model-like, one would need the loop
to "overshoot," not only canceling the top contribution but producing an
opposite-sign hGG vertex of about the same magnitude as that in the SM. We
argue that most such explanations have severe problems with fine-tuning and,
more importantly, vacuum stability. In particular, the case of stop loops
producing an opposite-sign hGG vertex of the same size as the Standard Model
one is ruled out by a combination of vacuum decay bounds and LEP constraints.
We also show that scenarios with a sign flip from loops of color octet charged
scalars or new fermionic states are highly constrained.Comment: 20 pages, 8 figures; v2: references adde