102 research outputs found
Search for the Top Partner at the LHC using Multi-b-Jet Channels
Vector-like quarks are introduced in various new physics models beyond the
standard model (SM) at the TeV scale. We especially consider the case that the
quark is singlet (triplet) under the SU(2) (SU(3)) gauge group and
couples only to the third generation quarks of the SM. The vector-like quark of
this kind is often called a top partner. The top partoner decays into
and . In the ATLAS and CMS collaborations, the top partner has
been searched in the final states of and , while the search based on
the decay mode has not been started yet. However, the decay into
is important since it is significantly enhanced if some strong dynamics
exists in the TeV scale. In the presence of a light higgs boson, the decay mode
followed by produces three bottom quarks. We study
the sensitivity for the top partner using multi-b-jet events at the 8 TeV run
of the LHC experiment. The multi-b-jet eventss turn out to play a complementary
role to the existing and searches by the ATLAS and CMS
collaborations.Comment: 26 pages, 9 figures, 10 Table
Explosive Dark Matter Annihilation
If the Dark Matter (DM) in the Universe has interactions with the
standard-model particle, the pair annihilation may give the imprints in the
cosmic ray. In this paper we study the pair annihilation processes of the DM,
which is neutral, however has the electroweak (EW) gauge non-singlet. In this
estimation the non-relativistic (NR) effective theory in the EW sector is a
suitable technique. We find that if the DM mass is larger than about 1 TeV, the
attractive Yukawa potentials induced by the EW gauge bosons have significant
effects on the DM annihilation processes, and the cross sections may be
enhanced by several orders of magnitude, due to the zero energy resonance under
the potentials. Especially, the annihilation to two 's might have a
comparable cross section to other tree-level processes, while the cross section
under the conventional calculation is suppressed by a loop factor. We also
discuss future sensitivities to the ray from the galactic center by
the GLAST satellite detector and the Air Cerenkov Telescope (ACT) arrays.Comment: 5 pages, 6 Postscript figures, revte
Heavy Fermion Bound States for Diphoton Excess at 750GeV Collider and Cosmological Constraints
A colored heavy particle with sufficiently small width may form
non-relativistic bound states when they are produced at the large hadron
collider\,(LHC), and they can annihilate into a diphoton final state. The
invariant mass of the diphoton would be around twice of the colored particle
mass. In this paper, we study if such bound state can be responsible for the
750 GeV diphoton excess reported by ATLAS and CMS. We found that the best-fit
signal cross section is obtained for the SU(2) singlet colored fermion
with . Having such an exotic hypercharge, the particle is expected to
decay through some higher dimensional operators, consistent with the small
width assumption. The decay of may involve a stable particle , if
both and are odd under some conserved symmetry. In that case,
the particle suffers from the constraints of jets + missing searches
by ATLAS and CMS at 8 TeV and 13 TeV. We found that such a scenario still
survives if the mass difference between and is above 30 GeV
for GeV. Even assuming pair annihilation of is small, the
relic density of is small enough if the mass difference between and
is smaller than 40 GeV
Direct Detection of the Wino- and Higgsino-like Neutralino Dark Matters at One-Loop Level
The neutralino-nucleon (\tilde{\chi}^0-N) scattering is an important process
for direct dark matter searches. In this paper we discuss one-loop
contributions to the cross section in the wino-like and Higgsino-like LSP
cases. The neutralino-nucleon scattering mediated by the Higgs
\tilde{\chi}^0\tilde{\chi}^0 and Z\tilde{\chi}^0\tilde{\chi}^0 couplings at
tree level is suppressed by the gaugino-Higgsino mixing at tree level when the
neutralino is close to a weak eigenstate. The one-loop contribution to the
cross section, generated by the gauge interaction, is not suppressed by any
SUSY particle mass or mixing in the wino- and Higgsino-like LSP cases. It may
significantly alter the total cross section when \sigma_{\tilde{\chi}^0 N}\sim
10^{-45} cm^2 or less.Comment: 26 pages, 9 figures. Version to be published in Physical Review
Non-Perturbative Effect on Dark Matter Annihilation and Gamma Ray Signature from Galactic Center
Detection of gamma rays from dark matter annihilation in the galactic center
is one of the feasible techniques to search for dark matter. We evaluate the
gamma ray flux in the case that the dark matter has an electroweak SU(2)_L
charge. Such dark matter is realized in the minimal supersymmetric standard
model (MSSM) when the lightest SUSY particle is the Higgsino- or Wino-like
neutralino. When the dark matter is heavy compared to the weak gauge bosons,
the leading-order calculation of the annihilation cross sections in
perturbation breaks down due to a threshold singularity. We take into account
non-perturbative effects by using the non-relativistic effective theory for the
two-body states of the dark matter and its SU(2)_L partner(s), and evaluate
precise cross sections relevant to the gamma ray fluxes. We find that the
annihilation cross sections may be enhanced by several orders of magnitude due
to resonances when the dark matter mass is larger than 1 TeV. Furthermore, the
annihilation cross sections in the MSSM may be changed by factors even when the
mass is about 500 GeV. We also discuss sensitivities to gamma ray signals from
the galactic center in the GLAST satellite detector and the large Air Cerenkov
Telescope arrays.Comment: 44 pages, 25 figures, some typos in Sec.V-2 (related to fitting
functions) correcte
コウレイシャ ニュウショ シセツ ニオケル ニンチショウ コウレイシャ オ タイショウ トシタ ソーシャルワーク ジッセン ノ コンナンセイ ニ カンスル ケンキュウ : フォーカス グループ インタビュー チョウサ カラ シサ サレル バリテーション ノ カツヨウ ニ ムケタ ケントウ
Role of the VEGF-Flt-1-FAK pathway in the pathogenesis of osteoclastic bone destruction of giant cell tumors of bone
BACKGROUND: Giant cell tumors (GCTs) of bone are primary benign bone tumors that are characterized by a high number of osteoclast-like multinuclear giant cells (MNCs). Recent studies suggest that the spindle-shaped stromal cells in GCTs are tumor cells, while monocyte-like cells and MNCs are reactive osteoclast precursor cells (OPCs) and osteoclasts (OCs), respectively. In this study, we investigated the pathogenesis of osteoclastic bone destruction in GCTs by focusing on the role of the vascular endothelial growth factor (VEGF)-Flt-1 (type-1 VEGF receptor)-focal adhesion kinase (FAK) pathway. METHODS: The motility of OPCs cells was assessed by a chemotaxis assay and the growth of OPCs was examined using a cell proliferation assay. The expression of VEGF and activation of Flt-1 and FAK in clinical GCT samples and in OPCs were detected by immunohistochemistry and immunoblotting. The correlation between the expression levels of activated Flt-1 and FAK and clinical stages of GCTs was investigated by immunohistochemistry. RESULTS: In GCT samples, CD68, a marker of OPCs and OCs, co-localized with Flt-1. Conditioned media from GCT tissue (GCT-CM) enhanced the chemotaxis and proliferation of OPCs. GCT-CM also stimulated FAK activation in OPCs in vitro. Moreover, there was a correlation between the clinical stage of GCTs and the expression of tyrosine-phosphorylated Flt-1 and FAK. CONCLUSIONS: Our results suggest that the VEGF-Flt-1-FAK pathway is involved in the pathogenesis of bone destruction of GCTs
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