608 research outputs found
Partially Composite Higgs in Supersymmetry
We propose a framework for natural breaking of electroweak symmetry in
supersymmetric models, where elementary Higgs fields are semi-perturbatively
coupled to a strong superconformal sector. The Higgs VEVs break conformal
symmetry in the strong sector at the TeV scale, and the strong sector in turn
gives important contributions to the Higgs potential, giving rise to a kind of
Higgs bootstrap. A Higgs with mass 125\GeV can be accommodated without any
fine tuning. A Higgsino mass of order the Higgs mass is also dynamically
generated in these models. The masses in the strong sector generically violate
custodial symmetry, and a good precision electroweak fit requires tuning of
order . The strong sector has an approximately supersymmetric
spectrum of hadrons at the TeV scale that can be observed by looking for a peak
in the invariant mass distribution, as well as final states containing
multiple , , and Higgs bosons. The models also generically predict large
corrections (either enhancement or suppression) to the h \to \ga\ga width.Comment: 31 page
Suppressing Electroweak Precision Observables in 5D Warped Models
We elaborate on a recently proposed mechanism to suppress large contributions
to the electroweak precision observables in five dimensional (5D) warped
models, without the need for an extended 5D gauge sector. The main ingredient
is a modification of the AdS metric in the vicinity of the infrared (IR) brane
corresponding to a strong deviation from conformality in the IR of the 4D
holographic dual. We compute the general low energy effective theory of the 5D
warped Standard Model, emphasizing additional IR contributions to the wave
function renormalization of the light Higgs mode. We also derive expressions
for the S and T parameters as a function of a generic 5D metric and zero-mode
wave functions. We give an approximate formula for the mass of the radion that
works even for strong deviation from the AdS background. We proceed to work out
the details of an explicit model and derive bounds for the first KK masses of
the various bulk fields. The radion is the lightest new particle although its
mass is already at about 1/3 of the mass of the lightest resonances, the KK
states of the gauge bosons. We examine carefully various issues that can arise
for extreme choices of parameters such as the possible reintroduction of the
hierarchy problem, the onset of nonperturbative physics due to strong IR
curvature or the creation of new hierarchies near the Planck scale. We conclude
that a KK scale of 1 TeV is compatible with all these constraints.Comment: 44 pages, 11 figures, references adde
The Maximal Inverse Seesaw from Operator and Oscillating Asymmetric Sneutrino Dark Matter
The maximal supersymmetric inverse seesaw mechanism (MSIS)
provides a natural way to relate asymmetric dark matter (ADM) with neutrino
physics. In this paper we point out that, MSIS is a natural outcome if one
dynamically realizes the inverse seesaw mechanism in the next-to minimal
supersymmetric standard model (NMSSM) via the dimension-five operator
, with the NMSSM singlet developing TeV scale VEV; it
slightly violates lepton number due to the suppression by the fundamental scale
, thus preserving maximally. The resulting sneutrino is a
distinguishable ADM candidate, oscillating and favored to have weak scale mass.
A fairly large annihilating cross section of such a heavy ADM is available due
to the presence of singlet.Comment: journal versio
Stealth Supersymmetry
We present a broad class of supersymmetric models that preserve R-parity but
lack missing energy signatures. These models have new light particles with
weak-scale supersymmetric masses that feel SUSY breaking only through couplings
to the MSSM. This small SUSY breaking leads to nearly degenerate fermion/boson
pairs, with small mass splittings and hence small phase space for decays
carrying away invisible energy. The simplest scenario has low-scale SUSY
breaking, with missing energy only from soft gravitinos. This scenario is
natural, lacks artificial tunings to produce a squeezed spectrum, and is
consistent with gauge coupling unification. The resulting collider signals will
be jet-rich events containing false resonances that could resemble signatures
of R-parity violation. We discuss several concrete examples of the general
idea, and emphasize gamma + jet + jet resonances, displaced vertices, and very
large numbers of b-jets as three possible discovery modes.Comment: 12 pages, 4 figure
Single production of the top partners at high energy colliders
The left-right twin () model is a concrete realization of the
twin mechanism, which predicts the existence of the top partner . In
this paper, we consider production of associated with the top quark at
the high energy linear collider () and the experiments,
and its single production in future linac-ring type collider experiment.
To compare our results with those of the littlest model with
-parity, we also estimate production of the -even top partner via
the corresponding processes in these high energy collider experiments. A simply
phenomenological analysis is also given.Comment: 21 pages, 10 figures; to be published in Nucl. Phys.
Metabolic flexibility as a major predictor of spatial distribution in microbial communities
A better understand the ecology of microbes and their role in the global ecosystem could be achieved if traditional ecological theories can be applied to microbes. In ecology organisms are defined as specialists or generalists according to the breadth of their niche. Spatial distribution is often used as a proxy measure of niche breadth; generalists have broad niches and a wide spatial distribution and specialists a narrow niche and spatial distribution. Previous studies suggest that microbial distribution patterns are contrary to this idea; a microbial generalist genus (Desulfobulbus) has a limited spatial distribution while a specialist genus (Methanosaeta) has a cosmopolitan distribution. Therefore, we hypothesise that this counter-intuitive distribution within generalist and specialist microbial genera is a common microbial characteristic. Using molecular fingerprinting the distribution of four microbial genera, two generalists, Desulfobulbus and the methanogenic archaea Methanosarcina, and two specialists, Methanosaeta and the sulfate-reducing bacteria Desulfobacter were analysed in sediment samples from along a UK estuary. Detected genotypes of both generalist genera showed a distinct spatial distribution, significantly correlated with geographic distance between sites. Genotypes of both specialist genera showed no significant differential spatial distribution. These data support the hypothesis that the spatial distribution of specialist and generalist microbes does not match that seen with specialist and generalist large organisms. It may be that generalist microbes, while having a wider potential niche, are constrained, possibly by intrageneric competition, to exploit only a small part of that potential niche while specialists, with far fewer constraints to their niche, are more capable of filling their potential niche more effectively, perhaps by avoiding intrageneric competition. We suggest that these counter-intuitive distribution patterns may be a common feature of microbes in general and represent a distinct microbial principle in ecology, which is a real challenge if we are to develop a truly inclusive ecology
Asymmetric Inelastic Inert Doublet Dark Matter from Triplet Scalar Leptogenesis
The nature of dark matter (DM) particles and the mechanism that provides
their measured relic abundance are currently unknown. In this paper we
investigate inert scalar and vector like fermion doublet DM candidates with a
charge asymmetry in the dark sector, which is generated by the same mechanism
that provides the baryon asymmetry, namely baryogenesis-via-leptogenesis
induced by decays of scalar triplets. At the same time the model gives rise to
neutrino masses in the ballpark of oscillation experiments via type II seesaw.
We discuss possible sources of depletion of asymmetry in the DM and visible
sectors and solve the relevant Boltzmann equations for quasi-equilibrium decay
of triplet scalars. A Monte-Carlo-Markov-Chain analysis is performed for the
whole parameter space. The survival of the asymmetry in the dark sector leads
to inelastic scattering off nuclei. We then apply bayesian statistic to infer
the model parameters favoured by the current experimental data, in particular
the DAMA annual modulation and Xenon100 exclusion limit. The latter strongly
disfavours asymmetric scalar doublet DM of mass \mathcal{O}(\TeV) as required
by DM- oscillations, while an asymmetric vector like fermion
doublet DM with mass around 100 GeV is a good candidate for DAMA annual
modulation yet satisfying the constraints from Xenon100 data.Comment: 35 pages and 15 figures, references adde
Universal contributions to scalar masses from five dimensional supergravity
We compute the effective Kahler potential for matter fields in warped
compactifications, starting from five dimensional gauged supergravity, as a
function of the matter fields localization. We show that truncation to zero
modes is inconsistent and the tree-level exchange of the massive gravitational
multiplet is needed for consistency of the four-dimensional theory. In addition
to the standard Kahler coming from dimensional reduction, we find the quartic
correction coming from integrating out the gravity multiplet. We apply our
result to the computation of scalar masses, by assuming that the SUSY breaking
field is a bulk hypermultiplet. In the limit of extreme opposite localization
of the matter and the spurion fields, we find zero scalar masses, consistent
with sequestering arguments. Surprisingly enough, for all the other cases the
scalar masses are tachyonic. This suggests the holographic interpretation that
a CFT sector always generates operators contributing in a tachyonic way to
scalar masses. Viability of warped su- persymmetric compactifications
necessarily asks then for additional contributions. We discuss the case of
additional bulk vector multiplets with mixed boundary conditions, which is a
partic- ularly simple and attractive way to generate large positive scalar
masses. We show that in this case successful fermion mass matrices implies
highly degenerate scalar masses for the first two generations of squarks and
sleptons.Comment: 23 pages. v2: References added, new section on effect of additional
bulk vector multiplets and phenomenolog
Unifying darko-lepto-genesis with scalar triplet inflation
We present a scalar triplet extension of the standard model to unify the
origin of inflation with neutrino mass, asymmetric dark matter and
leptogenesis. In presence of non-minimal couplings to gravity the scalar
triplet, mixed with the standard model Higgs, plays the role of inflaton in the
early Universe, while its decay to SM Higgs, lepton and dark matter
simultaneously generate an asymmetry in the visible and dark matter sectors. On
the other hand, in the low energy effective theory the induced vacuum
expectation value of the triplet gives sub-eV Majorana masses to active
neutrinos. We investigate the model parameter space leading to successful
inflation as well as the observed dark matter to baryon abundance. Assuming the
standard model like Higgs mass to be at 125-126 GeV, we found that the mass
scale of the scalar triplet to be ~ O(10^9) GeV and its trilinear coupling to
doublet Higgs is ~ 0.09 so that it not only evades the possibility of having a
metastable vacuum in the standard model, but also lead to a rich
phenomenological consequences as stated above. Moreover, we found that the
scalar triplet inflation strongly constrains the quartic couplings, while
allowing for a wide range of Yukawa couplings which generate the CP asymmetries
in the visible and dark matter sectors.Comment: (v1) 29 pages, 11 figures; (v2) 30 pages, 1 figure added and
discussions expanded, to appear in Nuclear Physics
Theoretical Constraints on the Higgs Effective Couplings
We derive constraints on the sign of couplings in an effective Higgs
Lagrangian using prime principles such as the naturalness principle, global
symmetries, and unitarity. Specifically, we study four dimension-six operators,
O_H, O_y, O_g, and O_gamma, which contribute to the production and decay of the
Higgs boson at the Large Hadron Collider (LHC), among other things. Assuming
the Higgs is a fundamental scalar, we find: 1) the coefficient of O_H is
positive except when there are triplet scalars, resulting in a reduction in the
Higgs on-shell coupling from their standard model (SM) expectations if no other
operators contribute, 2) the linear combination of O_H and O_y controlling the
overall Higgs coupling to fermion is always reduced, 3) the sign of O_g induced
by a new colored fermion is such that it interferes destructively with the SM
top contribution in the gluon fusion production of the Higgs, if the new
fermion cancels the top quadratic divergence in the Higgs mass, and 4) the
correlation between naturalness and the sign of O_gamma is similar to that of
O_g, when there is a new set of heavy electroweak gauge bosons. Next
considering a composite scalar for the Higgs, we find the reduction in the
on-shell Higgs couplings persists. If further assuming a collective breaking
mechanism as in little Higgs theories, the coefficient of O_H remains positive
even in the presence of triplet scalars. In the end, we conclude that the gluon
fusion production of the Higgs boson is reduced from the SM rate in all
composite Higgs models. Our study suggests a wealth of information could be
revealed by precise measurements of the Higgs couplings, providing strong
motivations for both improving on measurements at the LHC and building a
precision machine such as the linear collider.Comment: 37 pages, one figure; v2: improved discussion on dispersion relation
and other minor modifications; version accepted for publication
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