242 research outputs found
Baryomorphosis: Relating the Baryon Asymmetry to the "WIMP Miracle"
We present a generic framework, "baryomorphosis", which modifies the baryon
asymmetry to be naturally of the order of a typical thermal relic WIMP density.
We consider a simple scalar-based model to show how this is possible. This
model introduces a sector in which a large initial baryon asymmetry is injected
into particles ("annihilons") phi_B, \bar{phi}_B of mass ~ 100 GeV - 1 TeV.
phi_B-\bar{phi}_B annihilations convert the initial phi_B, \bar{phi}_B
asymmetry to a final asymmetry with a thermal relic WIMP-like density. This
subsequently decays to a conventional baryon asymmetry whose magnitude is
naturally related to the density of thermal relic WIMP dark matter. In this way
the two coincidences of baryons and dark matter i.e. why their densities are
similar to each other and why they are both similar to a WIMP thermal relic
density (the "WIMP miracle"), may be understood. The model may be tested by the
production of annihilons at colliders.Comment: 7 pages, 2 figures; Modified to address B washout issue. Higgs
replaced by inert doublet, no mixing of annihilons. Version to be published
in PRD, typos correcte
Puzzles of Dark Matter - More Light on Dark Atoms?
Positive results of dark matter searches in experiments DAMA/NaI and
DAMA/LIBRA confronted with results of other groups can imply nontrivial
particle physics solutions for cosmological dark matter. Stable particles with
charge -2, bound with primordial helium in O-helium "atoms" (OHe), represent a
specific nuclear-interacting form of dark matter. Slowed down in the
terrestrial matter, OHe is elusive for direct methods of underground Dark
matter detection using its nuclear recoil. However, low energy binding of OHe
with sodium nuclei can lead to annual variations of energy release from OHe
radiative capture in the interval of energy 2-4 keV in DAMA/NaI and DAMA/LIBRA
experiments. At nuclear parameters, reproducing DAMA results, the energy
release predicted for detectors with chemical content other than NaI differ in
the most cases from the one in DAMA detector. Moreover there is no bound
systems of OHe with light and heavy nuclei, so that there is no radiative
capture of OHe in detectors with xenon or helium content. Due to dipole Coulomb
barrier, transitions to more energetic levels of Na+OHe system with much higher
energy release are suppressed in the correspondence with the results of DAMA
experiments. The proposed explanation inevitably leads to prediction of
abundance of anomalous Na, corresponding to the signal, observed by DAMA.Comment: Contribution to Proceedings of XIII Bled Workshop "What Comes beyond
the Standard Model?
Strong Interactive Massive Particles from a Strong Coupled Theory
Minimal walking technicolor models can provide a nontrivial solution for
cosmological dark matter, if the lightest technibaryon is doubly charged.
Technibaryon asymmetry generated in the early Universe is related to baryon
asymmetry and it is possible to create excess of techniparticles with charge
(-2). These excessive techniparticles are all captured by , creating
\emph{techni-O-helium} ``atoms'', as soon as is formed in Big
Bang Nucleosynthesis. The interaction of techni-O-helium with nuclei opens new
paths to the creation of heavy nuclei in Big Bang Nucleosynthesis. Due to the
large mass of technibaryons, the ``atomic'' gas decouples from the
baryonic matter and plays the role of dark matter in large scale structure
formation, while structures in small scales are suppressed. Nuclear
interactions with matter slow down cosmic techni-O-helium in Earth below the
threshold of underground dark matter detectors, thus escaping severe CDMS
constraints. On the other hand, these nuclear interactions are not sufficiently
strong to exclude this form of Strongly Interactive Massive Particles by
constraints from the XQC experiment. Experimental tests of this hypothesis are
possible in search for in balloon-borne experiments (or on the ground)
and for its charged techniparticle constituents in cosmic rays and
accelerators. The ``atoms'' can cause cold nuclear transformations in
matter and might form anomalous isotopes, offering possible ways to exclude (or
prove?) their existence.Comment: 41 pages, 4 figure
Dark Majorana Particles from the Minimal Walking Technicolor
We investigate the possibility of a dark matter candidate emerging from a
minimal walking technicolor theory. In this case techniquarks as well as
technigluons transform under the adjoint representation of SU(2) of
technicolor. It is therefore possible to have technicolor neutral bound states
between a techniquark and a technigluon. We investigate this scenario by
assuming that such a particle can have a Majorana mass and we calculate the
relic density. We identify the parameter space where such an object can account
for the full dark matter density avoiding constraints imposed by the CDMS and
the LEP experiments.Comment: 22 pages, 4 figure
Solving the cosmic lithium problems with primordial late-decaying particles
We investigate the modifications to predictions for the abundances of light
elements from standard Big-Bang nucleosynthesis when exotic late-decaying
particles with lifetimes exceeding ~1 sec are prominent in the early Universe.
Utilising a model-independent analysis of the properties of these long-lived
particles, we identify the parameter space associated with models that are
consistent with all observational data and hence resolve the much discussed
discrepancies between observations and theoretical predictions for the
abundances of Li^7 and Li^6.Comment: 6 pages, 3 figures, submitted to Physical Review D; minor changes to
reference
Smooth Hybrid Inflation and Non-Thermal Type II Leptogenesis
We consider a smooth hybrid inflation scenario based on a supersymmetric
SU(2)_L x SU(2)_R x U(1)_B-L model. The Higgs triplets involved in the model
play a key role in inflation as well as in explaining the observed baryon
asymmetry of the universe. We show that the baryon asymmetry can originate via
non-thermal triplet leptogenesis from the decay of SU(2)_L triplets, whose tiny
vacuum expectation values also provide masses for the light neutrinos.Comment: 9 pages, 2 figure
Simultaneous Generation of WIMP Miracle-like Densities of Baryons and Dark Matter
The observed density of dark matter is of the magnitude expected for a
thermal relic weakly-interacting massive particle (WIMP). In addition, the
observed baryon density is within an order of magnitude of the dark matter
density. This suggests that the baryon density is physically related to a
typical thermal relic WIMP dark matter density. We present a model which
simultaneously generates thermal relic WIMP-like densities for both baryons and
dark matter by modifying a large initial baryon asymmetry. Dark matter is due
to O(100) GeV gauge singlet scalars produced in the annihilation of the O(TeV)
coloured scalars which are responsible for the final thermal WIMP-like baryon
asymmetry. The requirement of no baryon washout implies that there are two
gauge singlet scalars. The low temperature transfer of the asymmetry to
conventional baryons can be understood if the long-lived O(TeV) coloured
scalars have large hypercharge, |Y| > 4/3. Production of such scalars at the
LHC would be a clear signature of the model.Comment: 12 pages, 5 figures, overdue correction of typos, version published
PR
Population III Star Formation in a Lambda WDM Universe
In this paper we examine aspects of primordial star formation in a gravitino
warm dark matter universe with a cosmological constant. We compare a set of
simulations using a single cosmological realization but with a wide range of
warm dark matter particle masses which have not yet been conclusively ruled out
by observations. The addition of a warm dark matter component to the initial
power spectrum results in a delay in the collapse of high density gas at the
center of the most massive halo in the simulation and, as a result, an increase
in the virial mass of this halo at the onset of baryon collapse. Both of these
effects become more pronounced as the warm dark matter particle mass becomes
smaller. A cosmology using a gravitino warm dark matter power spectrum assuming
a particle mass of m_{WDM} ~ 40keV is effectively indistinguishable from the
cold dark matter case, whereas the m_{WDM} ~ 15 keV case delays star formation
by approx. 10^8 years. There is remarkably little scatter between simulations
in the final properties of the primordial protostar which forms at the center
of the halo, possibly due to the overall low rate of halo mergers which is a
result of the WDM power spectrum. The detailed evolution of the collapsing halo
core in two representative WDM cosmologies is described. At low densities
(n_{b} <= 10^5 cm^{-3}), the evolution of the two calculations is qualitatively
similar, but occurs on significantly different timescales, with the halo in the
lower particle mass calculation taking much longer to evolve over the same
density range and reach runaway collapse. Once the gas in the center of the
halo reaches relatively high densities (n_{b} >= 10^5 cm^{-3}) the overall
evolution is essentially identical in the two calculations.Comment: 36 pages, 12 figures (3 color). Astrophysical Journal, accepte
Dark Matter Antibaryons from a Supersymmetric Hidden Sector
The cosmological origin of both dark and baryonic matter can be explained
through a unified mechanism called hylogenesis where baryon and antibaryon
number are divided between the visible sector and a GeV-scale hidden sector,
while the Universe remains net baryon symmetric. The "missing" antibaryons, in
the form of exotic hidden states, are the dark matter. We study model-building,
cosmological, and phenomenological aspects of this scenario within the
framework of supersymmetry, which naturally stabilizes the light hidden sector
and electroweak mass scales. Inelastic dark matter scattering on visible matter
destroys nucleons, and nucleon decay searches offer a novel avenue for the
direct detection of the hidden antibaryonic dark matter sea.Comment: 33 pages, 10 figures. Minor changes to match published versio
Cosmic Strings as Emitters of Extremely High Energy Neutrinos
We study massive particle radiation from cosmic string kinks, and its
observability in extremely high energy neutrinos. In particular, we consider
the emission of moduli --- weakly coupled scalar particles predicted in
supersymmetric theories --- from the kinks of cosmic string loops. Since kinks
move at the speed of light on strings, moduli are emitted with large Lorentz
factors, and eventually decay into many pions and neutrinos via hadronic
cascades. The produced neutrino flux has energy ,
and is affected by oscillations and absorption (resonant and non-resonant). It
is observable at upcoming neutrino telescopes such as JEM-EUSO, and the radio
telescopes LOFAR and SKA, for a range of values of the string tension, and of
the mass and coupling constant of the moduli.Comment: 13 pages, 2 figure
- …