207 research outputs found
Relic Neutralino Density in Scenarios with Intermediate Unification Scale
We analyse the relic neutralino density in supersymmetric models with an
intermediate unification scale. In particular, we present concrete cosmological
scenarios where the reheating temperature is as small as
MeV). When this temperature is associated to the decay of moduli fields
producing neutralinos, we show that the relic abundance increases considerably
with respect to the standard thermal production. Thus the neutralino becomes a
good dark matter candidate with 0.1\lsim \Omega h^2 \lsim 0.3, even for
regions of the parameter space where large neutralino-nucleon cross sections,
compatible with current dark matter experiments, are present. This is obtained
for intermediate scales GeV, and moduli masses
GeV. On the other hand, when the above temperature is
associated to the decay of an inflaton field, the relic abundance is too small.Comment: Latex, 11 pages, 2 figure
Supersymmetric Musings on the Predictivity of Family Symmetries
We discuss the predictivity of family symmetries for the soft supersymmetry
breaking parameters in the framework of supergravity. We show that unknown
details of the messenger sector and the supersymmetry breaking hidden sector
enter into the soft parameters, making it difficult to obtain robust
predictions. We find that there are specific choices of messenger fields which
can improve the predictivity for the soft parameters.Comment: 20 pages, 5 figure
Complete genome sequences of two Citrobacter rodentium bacteriophages, CR8 and CR44b
© 2014 Toribio et al. The complete genomes of two virulent phages infecting Citrobacter rodentium are reported here for the first time. Both bacteriophages were isolated from local sewage treatment plant effluents. Genome analyses revealed a close relationship between both phages and allowed their classification as members of the Autographivirinae subfamily in the T7-like genus
Impact of DM direct searches and the LHC analyses on branon phenomenology
Dark Matter direct detection experiments are able to exclude interesting
parameter space regions of particle models which predict an important amount of
thermal relics. We use recent data to constrain the branon model and to compute
the region that is favored by CDMS measurements. Within this work, we also
update present colliders constraints with new studies coming from the LHC.
Despite the present low luminosity, it is remarkable that for heavy branons,
CMS and ATLAS measurements are already more constraining than previous analyses
performed with TEVATRON and LEP data.Comment: 17 pages, 2 figure
The Gravitino-Stau Scenario after Catalyzed BBN
We consider the impact of Catalyzed Big Bang Nucleosynthesis on theories with
a gravitino LSP and a charged slepton NLSP. In models where the gravitino to
gaugino mass ratio is bounded from below, such as gaugino-mediated SUSY
breaking, we derive a lower bound on the gaugino mass parameter m_1/2. As a
concrete example, we determine the parameter space of gaugino mediation that is
compatible with all cosmological constraints.Comment: 1+14 pages, 6 figures; v2: minor clarifications, 1 reference added,
matches version to appear in JCA
Phenomenology of heterotic M-theory with five-branes
We analyze some phenomenological implications of heterotic M-theory with
five-branes. Recent results for the effective 4-dimensional action are used to
perform a systematic analysis of the parameter space, finding the restrictions
that result from requiring the volume of the Calabi-Yau to remain positive.
Then the different scales of the theory, namely, the 11-dimensional Planck
mass, the compactification scale and the orbifold scale, are evaluated.
The expressions for the soft supersymmetry-breaking terms are computed and
discussed in detail for the whole parameter space. With this information we
study the theoretical predictions for the supersymmetric contribution to the
muon anomalous magnetic moment, using the recent experimental result as a
constraint on the parameter space. We finally analyze the neutralino as a dark
matter candidate in this construction. In particular, the neutralino-nucleon
cross-section is computed and compared with the sensitivities explored by
present dark matter detectors.Comment: Final version to appear in Phys. Rev. D. Some comments and references
added. 37 pages, 19 figure
Entropy production by Q-ball decay for diluting long-lived charged particles
The cosmic abundance of a long-lived charged particle such as a stau is
tightly constrained by the catalyzed big bang nucleosynthesis. One of the ways
to evade the constraints is to dilute those particles by a huge entropy
production. We evaluate the dilution factor in a case that non-relativistic
matter dominates the energy density of the universe and decays with large
entropy production. We find that large Q balls can do the job, which is
naturally produced in the gauge-mediated supersymmetry breaking scenario.Comment: 8 pages, 1 figur
Superstring Theory and CP- Violating Phases: Can They Be Related?
We investigate the possibility of large CP- violating phases in the soft
breaking terms derived in superstring models. The bounds on the electric dipole
moments (EDM's) of the electron and neutron are satisfied through cancellations
occuring because of the structure of the string models. Three general classes
of four-dimensional string models are considered: (i) orbifold
compactifications of perturbative heterotic string theory, (ii) scenarios based
on Ho\v{r}ava-Witten theory, and (iii) Type I string models (Type IIB
orientifolds). Nonuniversal phases of the gaugino mass parameters greatly
facilitate the necessary cancellations among the various contributions to the
EDM's; in the overall modulus limit, the gaugino masses are universal at tree
level in both the perturbative heterotic models and the Ho\v{r}ava-Witten
scenarios, which severely restricts the allowed regions of parameter space.
Nonuniversal gaugino masses do arise at one-loop in the heterotic orbifold
models, providing for corners of parameter space with phases
consistent with the phenomenological bounds. However, there is a possibility of
nonuniversal gaugino masses at tree level in the Type I models, depending on
the details of the embedding of the SM into the D- brane sectors. We find that
in a minimal model with a particular embedding of the Standard Model gauge
group into two D- brane sectors, viable large phase solutions can be obtained
over a wide range of parameter space.Comment: 28 pages, 6 figures; corrected bug in the code and a few typos,
results qualitatively unchange
Towards constraints on the SUSY seesaw from flavour-dependent leptogenesis
We systematically investigate constraints on the parameters of the
supersymmetric type-I seesaw mechanism from the requirement of successful
thermal leptogenesis in the presence of upper bounds on the reheat temperature
of the early Universe. To this end, we solve the
flavour-dependent Boltzmann equations in the MSSM, extended to include
reheating. With conservative bounds on , leading to mildly
constrained scenarios for thermal leptogenesis, compatibility with observation
can be obtained for extensive new regions of the parameter space, due to
flavour-dependent effects. On the other hand, focusing on (normal) hierarchical
light and heavy neutrinos, the hypothesis that there is no CP violation
associated with the right-handed neutrino sector, and that leptogenesis
exclusively arises from the CP-violating phases of the matrix,
is only marginally consistent. Taking into account stricter bounds on
further suggests that (additional) sources of CP violation must
arise from the right-handed neutrino sector, further implying stronger
constraints for the right-handed neutrino parameters.Comment: 42 pages, 12 figures; final version published in JCAP; numerical
results for the efficiency factor can be downloaded from
http://www.newphysics.eu/leptogenesis
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