2,062 research outputs found
Symmetry breaking and electroweak physics at Photon Linear Colliders
The physics potential of a high-energy photon collider is reviewed. The
emphasis is put on aspects related to the symmetry breaking sector, including
Higgs searches and production of longitudinal vector bosons.Comment: LATEX, 12 pages, 3 fig, macros included, no changes in pape
Dark matter and the LHC
Cosmological and astrophysical measurements indicate that the universe
contains a large amount of dark matter. A number of weak scale dark matter
candidates have been proposed in extensions of the standard model. The
potential to discover the dark matter particle and determine its properties at
the upcoming LHC is summarized.Comment: 6 pages, 4 figures, Talk at Dark matter and dark energy, GGI,
Florence, Italy, March 200
Assisted freeze-out
We explore a class of dark matter models with two dark matter candidates,
only one interacts with the standard model sector. One of the dark matter is
thermalized with the assistance of the other stable particle. While both stable
particles contribute to the total relic density only one can elastically
scatter with nuclei, thus effectively reducing the direct detection rate.Comment: 16 pages, 13 figures, minor corrections, the final version published
in JCA
Invisible Decays of the Supersymmetric Higgs and Dark Matter
We discuss effects of the light sparticles on decays of the lightest Higgs in
a supersymmetric model with nonuniversal gaugino masses at the high scale,
focusing on the `invisible' decays into neutralinos. These can impact
significanlty the discovery possibilities of the lightest Higgs at the LHC. We
show that due to these decays, there exist regions of the space where
the B.R. becomes dangerously low even after imposing
the LEP constraints on the sparticle masses, implying a possible preclusion of
its discovery in the channel. We find that there exist regions
in the parameter space with acceptable relic density and where the ratio falls
below 0.6, implying loss of signal in the channel. These
regions correspond to masses which should be
accessible already at the Tevatron. Further we find that considerations of
relic density put lower limit on the U(1) gaugino mass parameter
independently of and .Comment: 17 pages, 11 figures, Talk presented at Appi2002, Accelerator and
Particle Physics Institute, Appi, Iwate, Japan, February 13--16 200
Impact of semi-annihilations on dark matter phenomenology - an example of Z_N symmetric scalar dark matter
We study the impact of semi-annihilations x_i x_j x_k X, where x_i is any
dark matter and X is any standard model particle, on dark matter phenomenology.
We formulate minimal scalar dark matter models with an extra doublet and a
complex singlet that predict non-trivial dark matter phenomenology with
semi-annihilation processes for different discrete Abelian symmetries Z_N, N>2.
We implement two such example models with Z_3 and Z_4 symmetry in micrOMEGAs
and work out their phenomenology. We show that both semi-annihilations and
annihilations involving only particles from two different dark matter sectors
significantly modify the dark matter relic abundance in this type of models. We
also study the possibility of dark matter direct detection in XENON100 in those
models.Comment: 17 pages, 4 figure
Status and prospects of the nMSSM after LHC Run-1
The new minimal supersymmetric standard model (nMSSM), a variant of the
general next to minimal supersymmetric standard model (NMSSM) without
symmetry, features a naturally light singlino with a mass below 75 GeV. In
light of the new constraints from LHC Run-1 on the Higgs couplings, sparticles
searches and flavour observables, we define the parameter space of the model
which is compatible with both collider and dark matter (DM) properties. Among
the regions compatible with these constraints, implemented through NMSSMTools,
SModelS and MadAnalysis 5, only one with a singlino lightest supersymmetric
particle (LSP) with a mass around 5 GeV can explain all the DM abundance of the
universe, while heavier mixed singlinos can only form one of the DM components.
Typical collider signatures for each region of the parameter space are
investigated. In particular, the decay of the 125 GeV Higgs into light scalars
and/or pseudoscalars and the decay of the heavy Higgs into charginos and
neutralinos, provide distinctive signatures of the model. Moreover, the
sfermion decays usually proceed through heavier neutralinos rather than
directly into the LSP, as the couplings to the singlino are suppressed. We also
show that direct detection searches are complementary to collider ones, and
that a future ton-scale detector could completely probe the region of parameter
space with a LSP mass around 65 GeV.Comment: 33 pages, 9 figures. Version accepted for publication in JHE
Uncertainties in the Prediction of the Relic Density of Supersymmetric Dark Matter
We investigate how well the relic density of dark matter can be predicted in
mSUGRA. We determine the parameters to which the relic density is most
sensitive and quantify the collider accuracy needed to match the accuracy of
WMAP and PLANCK.Comment: 4 pages, 1 figure, presented at LCWS, Paris, April 200
Higgs Phenomenology of Minimal Universal Extra Dimensions
The minimal model of Universal Extra Dimensions (MUED) is briefly reviewed.
We explain how the cross-sections for Higgs production via gluon fusion and
decay into two photons are modified, relative the the Standard Model (SM)
values, by KK particles running in loops, leading to an enhancement of the gg
to h to two photons and gg to h to W+W- cross-sections. ATLAS and CMS searches
for the SM Higgs in these channels are reinterpreted in the context of MUED and
used to place new limits on the MUED parameter space. Only a small region of
between 1 and 3 GeV around mh = 125 GeV for 500 GeV < 1/R < 1600 GeV remains
open at the 95 % confidence level.Comment: Presented at the 2011 Hadron Collider Physics symposium (HCP-2011),
Paris, France, November 14-18 2011, 3 pages, 4 figure
Comparison of SUSY spectrum calculations and impact on the relic density constraints from WMAP
We compare results of four public supersymmetric (SUSY) spectrum codes,
Isajet, Softsusy, Spheno and Suspect to estimate the present-day uncertainty in
the calculation of the relic density of dark matter in mSUGRA models. We find
that even for mass differences of about 1% the spread in the obtained relic
densities can be 10%. In difficult regions of the parameter space, such as
large tan(beta) or large m_0, discrepancies in the relic density are much
larger. We also find important differences in the stau co-annihilation region.
We show the impact of these uncertainties on the bounds from WMAP for several
scenarios, concentrating on the regions of parameter space most relevant for
collider phenomenology. We also discuss the case of non-zero A_0 and the stop
co-annihilation region. Moreover, we present a web application for the online
comparison of the spectrum codes.Comment: 26 pages, 6 figures, 10 tables; version to appear in PR
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