173 research outputs found
Supersymmetry in Slow Motion
We construct new theories of electroweak symmetry breaking that employ a
combination of supersymmetry and discrete symmetries to stabilize the weak
scale up to and beyond the energies probed by the LHC. These models exhibit
conventional supersymmetric spectra but the fermion-sfermion-gaugino vertices
are absent. This closes many conventional decay channels, thereby allowing
several superpartners to be stable on collider time scales. This opens the door
to the possibility of directly observing R-hadrons and three flavors of
sleptons inside the LHC detectors.Comment: A reference added. The discussion on the Higgs sector expanded. The
version accepted for publication in JHE
Conformal Technicolor
We point out that the flavor problem in theories with dynamical electroweak
symmetry breaking can be effectively decoupled if the physics above the TeV
scale is strongly conformal, and the electroweak order parameter has a scaling
dimension d = 1 + epsilon with epsilon \simeq 1/few. There are many
restrictions on small values of epsilon: for epsilon << 1, electroweak symmetry
breaking requires a fine-tuning similar to that of the standard model; large-N
conformal field theories (including those obtained from the AdS/CFT
correspondence) require fine-tuning for d < 2; `walking technicolor' theories
cannot have d < 2, according to gap equation analyses. However, strong small-N
conformal field theories with epsilon \simeq 1/few avoid all these constraints,
and can give rise to natural dynamical electroweak symmetry breaking with a top
quark flavor scale of order 10^{1/epsilon} TeV, large enough to decouple
flavor. Small-N theories also have an acceptably small Peskin-Takeuchi S
parameter. This class of theories provides a new direction for dynamical
electroweak symmetry breaking without problems from flavor or electroweak
precision tests. A possible signal for these theories is a prominent scalar
resonance below the TeV scale with couplings similar to a heavy standard model
Higgs.Comment: 26 pages + References. Slight wording changes. Version appearing in
JHE
Composite Dirac Neutrinos
We present a mechanism that naturally produces light Dirac neutrinos. The
basic idea is that the right-handed neutrinos are composite. Any realistic
composite model must involve `hidden flavor' chiral symmetries. In general some
of these symmetries may survive confinement, and in particular, one of them
manifests itself at low energy as an exact symmetry. Dirac neutrinos are
therefore produced. The neutrinos are naturally light due to compositeness. In
general, sterile states are present in the model, some of them can naturally be
warm dark matter candidates.Comment: 12 pages; Sec. IIC updated; minor corrections; published versio
Low Energy 6-Dimensional N=2 Supersymmertric SU(6) Models on Orbifolds
We propose low energy 6-dimensional N=2 supersymmetric SU(6) models on
and , where the orbifold
model can be embedded on the boundary 4-brane. For the
zero modes, the 6-dimensional N=2 supersymmetry and the SU(6) gauge symmetry
are broken down to the 4-dimensional N=1 supersymmetry and the gauge symmetry by orbifold projections. In
order to cancel the anomalies involving at least one , we add extra
exotic particles. We also study the anomaly free conditions and present some
anomaly free models. The gauge coupling unification can be achieved at TeV if the compactification scale for the fifth dimension is
TeV. The proton decay problem can be avoided by putting the quarks and
leptons/neutrinos on different 3-branes. And we discuss how to break the
gauge symmetry, solve the
problem, and generate the mass hierarchy naturally by using the
geometry. The masses of exotic particles can be at the order of 1 TeV after the
gauge symmetry breaking. We also forbid the dimension-5 operators for the
neutrino masses by gauge symmetry, and the realistic left-handed
neutrino masses can be obtained via non-renormalizable terms.Comment: Latex, 33 pages, discussion and references adde
A novel PI3K inhibitor iMDK suppresses non-small cell lung Cancer cooperatively with A MEK inhibitor
The PI3KâAKT pathway is expected to be a therapeutic target for non-small cell lung cancer (NSCLC) treatment. We previously reported that a novel PI3K inhibitor iMDK suppressed NSCLC cells in vitro and in vivo without harming normal cells and mice. Unexpectedly, iMDK activated the MAPK pathway, including ERK, in the NSCLC cells. Since iMDK did not eradicate such NSCLC cells completely, it is possible that the activated MAPK pathway confers resistance to the NSCLC cells against cell death induced by iMDK. In the present study, we assessed whether suppressing of iMDK-mediated activation of the MAPK pathway would enhance anti-tumorigenic activity of iMDK. PD0325901, a MAPK inhibitor, suppressed the MAPK pathway induced by iMDK and cooperatively inhibited cell viability and colony formation of NSCLC cells by inducing apoptosis in vitro. HUVEC tube formation, representing angiogenic processes in vitro, was also cooperatively inhibited by the combinatorial treatment of iMDK and PD0325901. The combinatorial treatment of iMDK with PD0325901 cooperatively suppressed tumor growth and tumor-associated angiogenesis in a lung cancer xenograft model in vivo. Here, we demonstrate a novel treatment strategy using iMDK and PD0325901 to eradicate NSCLC
Vectorlike Confinement at the LHC
We argue for the plausibility of a broad class of vectorlike confining gauge
theories at the TeV scale which interact with the Standard Model predominantly
via gauge interactions. These theories have a rich phenomenology at the LHC if
confinement occurs at the TeV scale, while ensuring negligible impact on
precision electroweak and flavor observables. Spin-1 bound states can be
resonantly produced via their mixing with Standard Model gauge bosons. The
resonances promptly decay to pseudo-Goldstone bosons, some of which promptly
decay to a pair of Standard Model gauge bosons, while others are charged and
stable on collider time scales. The diverse set of final states with little
background include multiple photons and leptons, missing energy, massive stable
charged particles and the possibility of highly displaced vertices in dilepton,
leptoquark or diquark decays. Among others, a novel experimental signature of
resonance reconstruction out of massive stable charged particles is
highlighted. Some of the long-lived states also constitute Dark Matter
candidates.Comment: 33 pages, 6 figures. v4: expanded discussion of Z_2 symmetry for
stability, one reference adde
KeV Warm Dark Matter and Composite Neutrinos
Elementary keV sterile Dirac neutrinos can be a natural ingredient of the
composite neutrino scenario. For a certain class of composite neutrino
theories, these sterile neutrinos naturally have the appropriate mixing angles
to be resonantly produced warm dark matter (WDM). Alternatively, we show these
sterile neutrinos can be WDM produced by an entropy-diluted thermal freeze-out,
with the necessary entropy production arising not from an out-of-equilibrium
decay, but rather from the confinement of the composite neutrino sector,
provided there is sufficient supercooling.Comment: 12 pages, 2 figures, published versio
Neutrino Mass and from a Mini-Seesaw
The recently proposed "mini-seesaw mechanism" combines naturally suppressed
Dirac and Majorana masses to achieve light Standard Model neutrinos via a
low-scale seesaw. A key feature of this approach is the presence of multiple
light (order GeV) sterile-neutrinos that mix with the Standard Model. In this
work we study the bounds on these light sterile-neutrinos from processes like
\mu ---> e + \gamma, invisible Z-decays, and neutrinoless double beta-decay. We
show that viable parameter space exists and that, interestingly, key
observables can lie just below current experimental sensitivities. In
particular, a motivated region of parameter space predicts a value of BR(\mu
---> e + \gamma) within the range to be probed by MEG.Comment: 1+26 pages, 7 figures. v2 JHEP version (typo's fixed, minor change to
presentation, results unchanged
LHC String Phenomenology
We argue that it is possible to address the deeper LHC Inverse Problem, to
gain insight into the underlying theory from LHC signatures of new physics. We
propose a technique which may allow us to distinguish among, and favor or
disfavor, various classes of underlying theoretical constructions using
(assumed) new physics signals at the LHC. We think that this can be done with
limited data , and improved with more data. This is because of
two reasons -- a) it is possible in many cases to reliably go from
(semi)realistic microscopic string construction to the space of experimental
observables, say, LHC signatures. b) The patterns of signatures at the LHC are
sensitive to the structure of the underlying theoretical constructions. We
illustrate our approach by analyzing two promising classes of string
compactifications along with six other string-motivated constructions. Even
though these constructions are not complete, they illustrate the point we want
to emphasize. We think that using this technique effectively over time can
eventually help us to meaningfully connect experimental data to microscopic
theory.Comment: 50 Pages, 13 Figures, 3 Tables, v2: minor changes, references adde
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