134 research outputs found
Probing the Top-Yukawa Coupling in Associated Higgs production with a Single Top Quark
Associated production of the Higgs boson with a single top quark proceeds
through Feynman diagrams, which are either proportional to the hWW, top-Yukawa,
or the bottom-Yukawa couplings. It was shown in literature that the
interference between the top-Yukawa and the gauge-Higgs diagrams can be
significant, and thus the measurement of the cross sections can help pin down
the sign and the size of the top-Yukawa coupling. Here we perform a detailed
study with full detector simulations of such a possibility at the LHC-14 within
the current allowed range of hWW and top-Yukawa couplings, using h-> b b-bar,
\gamma\gamma, \tau+ \tau-, ZZ* -> 4 l modes. We found that the LHC-14 has the
potential to distinguish the size and the sign of the top-Yukawa coupling.
Among the channels the h-> b b-bar mode mode provides the best chance to probe
the signal, followed by the h -> \gamma\gamma\ mode, which has the advantage of
a narrow reconstructed mass peak. We also pointed out that the spatial
separation among the final-state particles has the potential in differentiating
among various values of the top-Yukawa coupling.Comment: 28 pages, 13 figures; a comment about NLO correction is added,
references added; match the published versio
An Exploratory study of Higgs-boson pair production
Higgs-boson pair production is well known being capable to probe the
trilinear self-coupling of the Higgs boson, which is one of the important
ingredients of the Higgs sector itself. Pair production then depends on the
top-quark Yukawa coupling , Higgs trilinear coupling ,
and a possible dim-5 contact-type coupling , which may
appear in some higher representations of the Higgs sector. We take into account
the possibility that the top-Yukawa and the couplings involved can be CP
violating. We calculate the cross sections and the interference terms as
coefficients of the square or the 4th power of each coupling at various stages of cuts, such that the desired
cross section under various cuts can be obtained by simply inputing the
couplings. We employ the decay mode of the
Higgs-boson pair to investigate the possibility of disentangle the triangle
diagram from the box digram so as to have a clean probe of the trilinear
coupling at the LHC. We found that the angular separation between the and
and that between the two photons is useful. We obtain the sensitivity
reach of each pair of couplings at the 14 TeV LHC and the future 100 TeV pp
machine. Finally, we also comment on using the decay
mode in Appendix.Comment: v3: 50 pages, 24 figures: 1 new CPV scenario and 3 new figures are
added; v4: published version, title changed in the journal versio
Entangling Higgs production associated with a single top and a top-quark pair in the presence of anomalous top-Yukawa coupling
The ATLAS and CMS collaborations observed a mild excess in the associated
Higgs production with a top-quark pair () and reported the signal
strengths of and based on the data collected at = 7 and 8 TeV.
Although, at the current stage, there is no obvious indication whether the
excess is real or due to statistical fluctuations, here we perform a case study
of this mild excess by exploiting the strong entanglement between the
associated Higgs production with a single top quark () and
production in the presence of anomalous top-Yukawa coupling. As well known,
production only depends on the absolute value of the top-Yukawa
coupling. Meanwhile, in production, this degeneracy is lifted through the
strong interference between the two main contributions which are proportional
to the top-Yukawa and the gauge-Higgs couplings, respectively. Especially, when
the relative sign of the top-Yukawa coupling with respect to the gauge-Higgs
coupling is reversed, the cross section can be enhanced by more than one
order of magnitude. We perform a detailed study of the influence of
production on production in the presence of the anomalous
top-Yukawa coupling and point out that it is crucial to include
production in the analysis of the data to pin down the sign and the
size of the top-Yukawa coupling in future. While assuming the Standard Model
(SM) value for the gauge-Higgs coupling, we vary the top-Yukawa coupling within
the range allowed by the current LHC Higgs data. We consider the Higgs decay
modes into multileptons, and putting a particular
emphasis on the same sign dilepton events. We also discuss ...Comment: 32 pages, 10 figures, 12 tables, to appear in JHE
Measuring properties of a Heavy Higgs boson in the decay
In many extensions of the standard model, there exist a few extra Higgs
bosons. Suppose a heavy neutral Higgs boson H is discovered at the LHC, one
could then investigate CP and CPT~ properties of its couplings to a pair of
bosons through . We use the helicity-amplitude method to
write down the most general form for the angular distributions of the four
final-state leptons, which can cover the case of CP-even, -odd, and -mixed
state for the Higgs boson. We figure out there are 9 types of angular
observables and all the couplings to bosons can be fully determined by
exploiting them. A Higgs-boson mass of 260 GeV below the threshold is
illustrated with full details. With a total of events of , one can determine the couplings up to 12-20\% uncertainties.Comment: 23 pages, 4 figures, 3 tables, to appear in JHE
A supersymmetric electroweak scale seesaw model
In this paper we propose a novel supersymmetric inverse seesaw model which
has only one additional symmetry. The field content is minimal to get a
viable neutrino spectrum at tree-level. Interestingly, the inverse seesaw scale
in our model is related to the scale of electroweak symmetry breaking. Due to
that origin we are less biased about hierarchies and discuss three different
types of the inverse seesaw mechanism with different phenomenologies. We can
successfully reproduce neutrino masses and mixing and our model is consistent
with current bounds on neutrinoless double beta decay, non-unitarity of the
PMNS matrix and charged lepton flavor violation.Comment: 20 pages, 1 figure; version published in JHE
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