455 research outputs found
Enhanced Charged Higgs Production through W-Higgs Fusion in W-b Scattering
We study the associated production of a charged Higgs boson with a bottom
quark and a light quark at the LHC via p p \to H^\pm\,b\,j in the Two Higgs
Doublet Models (2HDMs). Using the effective W approximation, we show that there
is exact cancellation among various Feynman diagrams in high energy limit. This
may imply that the production of charged Higgs can be significantly enhanced in
the presence of large mass differences among the neutral Higgs bosons via
W^\pm-Higgs fusion in the p p \to H^\pm\,b\,j process. Particularly, we
emphasize the potential enhancement due to a light pseudoscalar boson ,
which is still allowed by the current data by which we explicitly calculate the
allowed regions in (M_A,\,\tan\beta) plane, and show that the production cross
section can be as large as 0.1 pb for large . We also show that the
transverse momentum distribution of the b quark can potentially distinguish the
W^\pm-A fusion diagram from the top diagram. Finally, we point out further
enhancement when we go beyond the 2HDMs.Comment: 25 pages, 9 pdf figures, Matches the published JHEP 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
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
Signals of New Gauge Bosons in Gauged Two Higgs Doublet Model
Recently a gauged two Higgs doublet model, in which the two Higgs doublets
are embedded into the fundamental representation of an extra local
group, is constructed. Both the new gauge bosons and are electrically neutral. While can be singly produced at
colliders, , which is heavier, must be pair produced. We
explore the constraints of using the current Drell-Yan type data
from the Large Hadron Collider. Anticipating optimistically that can
be discovered via the clean Drell-Yan type signals at high luminosity upgrade
of the collider, we explore the detectability of extra heavy fermions in the
model via the two leptons/jets plus missing transverse energy signals from the
exotic decay modes of . For the pair production in
a future 100 TeV proton-proton collider, we demonstrate certain kinematical
distributions for the two/four leptons plus missing energy signals have
distinguishable features from the Standard Model background. In addition,
comparisons of these kinematical distributions between the gauged two Higgs
doublet model and the littlest Higgs model with T-parity, the latter of which
can give rise to the same signals with competitive if not larger cross
sections, are also presented.Comment: 39 pages, 23 figures, 7 tables and two new appendixes, to appear in
EPJ
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