492 research outputs found
AlterBBN: A program for calculating the BBN abundances of the elements in alternative cosmologies
We describe AlterBBN, a public C program for evaluating the abundances of the
elements generated by Big-Bang nucleosynthesis (BBN). This program enables the
user to compute the abundances of the elements in the standard model of
cosmology, and additionally provides possibilities to alter the assumptions of
the cosmological model in order to study their consequences on the abundances
of the elements. In particular the baryon-to-photon ratio and the effective
number of neutrinos, as well as the expansion rate and the entropy content of
the Universe during BBN can be modified in AlterBBN. Such features allow the
user to test the cosmological models by confronting them to BBN constraints. A
presentation of the physics of BBN and the features of AlterBBN is provided
here under the form of a manual.Comment: 15 pages, 1 figure, 1 table. AlterBBN can be obtained from
https://alterbbn.hepforge.org
Unifying dark energy and dark matter with a scalar field
The standard model of cosmology considers the existence of two components of
unknown nature, ``dark matter'' and ``dark energy'', which determine the
cosmological evolution. Their nature remains unknown, and other models can also
be considered. In particular, it may be possible to reinterpret the recent
cosmological observations so that the Universe does not contain two fluids of
unknown natures, but only one fluid with particular properties. After a brief
review of constraints on this unifying ``dark fluid'', we will discuss a
specific model of dark fluid based on a complex scalar fluid.Comment: 4 pages, 4 figures, to appear in the XXIst IAP Colloquium "Mass
Profiles and Shapes of Cosmological Structures", Paris 4-9 July 2005, France,
(Eds.) G. Mamon, F. Combes, C. Deffayet, B. Fort, EAS Publications Serie
Relic density and future colliders: inverse problem(s)
Relic density calculations are often used to constrain particle physics
models, and in particular supersymmetry. We will show that the presence of
additional energy or entropy before the Big-Bang nucleosynthesis can however
completely change the relic density constraints on the SUSY parameter space.
Therefore one should be extremely careful when using the relic density to
constrain supersymmetry as it could give misleading results, especially if
combined with the future collider data. Alternatively, we will also show that
combining the discoveries of the future colliders with relic density
calculations can shed light on the inaccessible pre-BBN dark time physics.
Finally we will present SuperIso Relic, a new relic density calculator code in
Supersymmetry, which incorporates alternative cosmological models, and is
publicly available.Comment: 8 pages, 5 figures, contribution to the proceedings of the conference
"Invisible Universe", Paris, June 29 - July 3, 2009, Franc
LHC and ILC Data and the Early Universe Properties
With the start-up of the LHC, we can hope to find evidences for new physics
beyond the Standard Model, and particle candidates for dark matter. Determining
the parameters of the full underlying theory will be a long process requiring
the combination of LHC and ILC data, flavor physics constraints, and
cosmological observations. However, the Very Early Universe properties, from
which the relic particles originate, are poorly known, and the relic density
calculation can be easily falsified by hidden processes. We consider
supersymmetry and show that determining the underlying particle physics
parameters will help understanding the Very Early Universe properties.Comment: 6 pages, 2 figures, contribution to the proceedings of the workshop
"LC09: e+e- Physics at the TeV Scale and the Dark Matter Connection",
Perugia, September 21 - 24, 2009, Italy. v2: reference adde
Dark Energy vs. Dark Matter: Towards a Unifying Scalar Field?
The standard model of cosmology suggests the existence of two components,
"dark matter" and "dark energy", which determine the fate of the Universe.
Their nature is still under investigation, and no direct proof of their
existences has emerged yet. There exist alternative models which reinterpret
the cosmological observations, for example by replacing the dark energy/dark
matter hypothesis by the existence of a unique dark component, the dark fluid,
which is able to mimic the behaviour of both components. After a quick review
of the cosmological constraints on this unifying dark fluid, we will present a
model of dark fluid based on a complex scalar field and discuss the problem of
the choice of the potential.Comment: 6 pages, 2 figures, contribution to the proceedings of the July 2008
CRAL-IPNL conference "Dark Energy and Dark Matter
Complementarity of direct and indirect searches in the pMSSM
We explore the pMSSM parameter space in view of the constraints from SUSY and
monojet searches at the LHC, from Higgs data and flavour physics observables,
as well as from dark matter searches. We show that whilst the simplest SUSY
scenarios are already ruled out, there are still many possibilities left over
in the pMSSM. We discuss the complementarity between different searches and
consistency checks which are essential in probing the pMSSM and will be even
more important in the near future with the next round of data becoming
available.Comment: 6 pages, 9 figures. Contribution to the proceedings of the Fifth
Capri Workshop on the interplay of flavour physics with electroweak symmetry
breaking and dark matter, Capri, May 201
Light neutralino dark matter in MSSM
Three dark matter direct detection experiments, DAMA, COGENT and CRESST, have
reported a possible signal of WIMP interaction corresponding to very light
particles, close to the edge of the XENON 100 and CDMS sensitivity. Imposing
the latest constraints from colliders, flavour physics, electroweak precision
tests and direct and indirect dark matter searches, we show that viable MSSM
scenarios with a light neutralino, in agreement with all the present data, are
feasible. An analysis of the characteristics of the resulting scenarios will be
presented.Comment: 6 pages, 2 figures, contribution to the ICHEP 2012 Conference
proceedings, 4-11 July 2012, Melbourne, Australi
Implications of LHC Higgs and SUSY searches for MSSM
The implications of the LHC SUSY searches as well as the discovery of a new
bosonic state compatible with the lightest Higgs boson will be discussed in the
context of constrained and general MSSM scenarios. Exploring the MSSM through
the Higgs sector is an alternative and complementary path to direct searches,
and tight constraints on the MSSM parameter space can be obtained.Comment: 7 pages, 5 figures, contribution to the ICHEP 2012 Conference
proceedings, 4-11 July 2012, Melbourne, Australi
An update of the constraints on the phenomenological MSSM from the new LHC Higgs results
Updated results on the search of Higgs bosons at the LHC with up to 17/fb of
data have just been presented by the ATLAS and CMS collaborations. New
constraints are provided by the LHCb and XENON experiments with the observation
of the rare decay B_s -> mu+mu- and new limits on dark matter direct detection.
In this paper, we update and extend the results on the implications of these
data on the phenomenological Minimal Supersymmetric extension of the Standard
Model (pMSSM) by using high statistics, flat scans of its 19 parameters. The
new LHC data on bb and tau tau decays of the lightest Higgs state and the new
CMS limits from the tau tau searches for the heavier Higgs states set stronger
constraints on the pMSSM parameter space.Comment: 14 pages, 8 figures. This update is based on results presented at HCP
2012 and the December 2012 CERN Council LHC Jamboree. It features larger scan
statistics and additional plot
Cosmological constraints on unifying Dark Fluid models
In the standard model of cosmology, dark matter and dark energy are presently
the two main contributors to the total energy in the Universe. However, these
two dark components are still of unknown nature, and many alternative
explanations are possible. We consider here the so-called unifying dark fluid
models, which replace dark energy and dark matter by a unique dark fluid with
specific properties. We will analyze in this context recent observational data
from supernovae of type Ia, large scale structures and cosmic microwave
background, as well as theoretical results of big-bang nucleosynthesis, in
order to derive constraints on the dark fluid parameters. We will also consider
constraints from local scales, and conclude with a brief study of a scalar
field dark fluid model.Comment: 11 pages, 1 figure, 1 tabl
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