364 research outputs found
Inverse seesaw and dark matter in models with exotic lepton triplets
We show that models with exotic leptons transforming as E ~ (1,3,-1) under
the standard model gauge symmetry are well suited for generating neutrino mass
via a radiative inverse seesaw. This approach realizes natural neutrino masses
and allows multiple new states to appear at the TeV scale. The exotic leptons
are therefore good candidates for new physics that can be probed at the LHC.
Furthermore, remnant low-energy symmetries ensure a stable dark matter
candidate, providing a link between dark matter and the origins of neutrino
mass.Comment: 6 pages, 3 figures (revtex4.1, two-columns
Inert Dark Matter and Strong Electroweak Phase Transition
The main virtue of the Inert Doublet Model (IDM) is that one of its spinless
neutral bosons can play the role of Dark Matter. Assuming that the additional
sources of CP violation are present in the form of higher dimensional
operator(s) we reexamine the possibility that the model parameters for which
the right number density of relic particles is predicted are compatible with
the first order phase transition that could lead to electroweak baryogenesis.
We find, taking into account recent indications from the LHC and the
constraints from the electroweak precision data, that for a light DM (40-60
GeV) particle and heavy almost degenerate additional scalars and
this is indeed possible but the two parameters most important for the strength
of the phase transition: the common mass of and and the trilinear
coupling of the Higgs-like particle to DM are strongly constrained. and
must weight less than GeV if the inert minimum is to be the
lowest one and the value of the coupling is limited by the XENON 100 data. We
stress the important role of the zero temperature part of the potential for the
strength of the phase transition.Comment: 15 pages, 5 figures, minor chnges, comment on h-->2gamma adde
Systematics of two-component superconductivity in from microwave measurements of high quality single crystals
Systematic microwave surface impedance measurements of YBCO single crystals
grown in crucibles reveal new properties that are not directly seen
in similar measurements of other YBCO samples. Two key observations obtained
from complex conductivity are: a new normal conductivity peak at around 80K and
additional pairing below 65K. High pressure oxygenation of one of the crystals
still yields the same results ruling out any effect of macroscopic segregation
of O-deficient regions. A single complex order parameter cannot describe these
data, and the results suggest at least two superconducting components.
Comparisons with model calculations done for various decoupled two-component
scenarios (i.e. s+d, d+d) are presented. Systematics of three single crystals
show that the 80K quasiparticle peak is correlated with the normal state
inelastic scattering rate. Close to Tc, the data follow a mean-field behavior.
Overall, our results strongly suggest the presence of multiple pairing
temperature and energy scales in .Comment: 14 pages, 2-column, Revtex, 5 embedded postscript figures, uses
graphicx. Postscript version also available at
http://sagar.physics.neu.edu/preprints.htm
Dark Matter and Neutrino Masses from Global Symmetry Breaking
We present a scenario where neutrino masses and Dark Matter are related due
to a global symmetry. Specifically we consider neutrino mass
generation via the Zee--Babu two-loop mechanism, augmented by a scalar singlet
whose VEV breaks the global symmetry. In order to obtain a Dark
Matter candidate we introduce two Standard Model singlet fermions. They form a
Dirac particle and are stable because of a remnant symmetry. Hence, in
this model the stability of Dark Matter follows from the global
symmetry. We discuss the Dark Matter phenomenology of the model, and compare it
to similar models based on gauged . We argue that in contrast to
the gauged versions, the model based on the global symmetry does not suffer
from severe constraints from searches.Comment: minor improvements, matches published versio
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
Implications of the 125 GeV Higgs boson for scalar dark matter and for the CMSSM phenomenology
We study phenomenological implications of the ATLAS and CMS hint of a GeV Higgs boson for the singlet, and singlet plus doublet non-supersymmetric
dark matter models, and for the phenomenology of the CMSSM. We show that in
scalar dark matter models the vacuum stability bound on Higgs boson mass is
lower than in the standard model and the 125 GeV Higgs boson is consistent with
the models being valid up the GUT or Planck scale. We perform a detailed study
of the full CMSSM parameter space keeping the Higgs boson mass fixed to GeV, and study in detail the freeze-out processes that imply the observed
amount of dark matter. After imposing all phenomenological constraints except
for the muon we show that the CMSSM parameter space is divided
into well separated regions with distinctive but in general heavy sparticle
mass spectra. Imposing the constraint introduces severe tension
between the high SUSY scale and the experimental measurements -- only the
slepton co-annihilation region survives with potentially testable sparticle
masses at the LHC. In the latter case the spin-independent DM-nucleon
scattering cross section is predicted to be below detectable limit at the
XENON100 but might be of measurable magnitude in the general case of light dark
matter with large bino-higgsino mixing and unobservably large scalar masses.Comment: 17 pages, 7 figures. v3: same as published versio
WIMP-nucleus scattering in chiral effective theory
We discuss long-distance QCD corrections to the WIMP-nucleon(s) interactions
in the framework of chiral effective theory. For scalar-mediated WIMP-quark
interactions, we calculate all the next-to-leading-order corrections to the
WIMP-nucleus elastic cross-section, including two-nucleon amplitudes and
recoil-energy dependent shifts to the single-nucleon scalar form factors. As a
consequence, the scalar-mediated WIMP-nucleus cross-section cannot be
parameterized in terms of just two quantities, namely the neutron and proton
scalar form factors at zero momentum transfer, but additional parameters
appear, depending on the short-distance WIMP-quark interaction. Moreover,
multiplicative factorization of the cross-section into particle, nuclear and
astro-particle parts is violated. In practice, while the new effects are of the
natural size expected by chiral power counting, they become very important in
those regions of parameter space where the leading order WIMP-nucleus amplitude
is suppressed, including the so-called "isospin-violating dark matter" regime.
In these regions of parameter space we find order-of-magnitude corrections to
the total scattering rates and qualitative changes to the shape of recoil
spectra.Comment: 23 pages, 6 figures, 1 tabl
The St\"{u}ckelberg Holographic Superconductors with Weyl corrections
In this letter we construct the St\"{u}ckelberg holographic superconductor
with Weyl corrections. Under such corrections, the Weyl coupling parameter
plays an important role in the order of phase transitions and the
critical exponents of second order phase transitions. So do the model
parameters , and . Moreover, we show that the Weyl
coupling parameter and the model parameters , ,
which together control the size and strength of the conductivity
coherence peak and the ratio of gap frequency over critical temperature
.Comment: 18 pages, 6 figure
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
Dark matter scenarios in the minimal SUSY B-L model
We perform a study of the dark matter candidates of a constrained version of
the minimal R-parity-conserving supersymmetric model with a gauged
. It turns out that there are four additional candidates for dark
matter in comparison to the MSSM: two kinds of neutralino, which either
correspond to the gaugino of the or to a fermionic bilepton, as
well as "right-handed" CP-even and -odd sneutrinos. The correct dark matter
relic density of the neutralinos can be obtained due to different mechanisms
including new co-annihilation regions and resonances. The large additional
Yukawa couplings required to break the radiatively often lead to
large annihilation cross sections for the sneutrinos. The correct treatment of
gauge kinetic mixing is crucial to the success of some scenarios. All
candidates are consistent with the exclusion limits of Xenon100.Comment: 45 pages, 22 figures; v2: extended discussion of direct detection
cross section, matches published versio
- …