333 research outputs found
Reach of the Fermilab Tevatron for minimal supergravity in the region of large scalar masses
The reach of the Fermilab Tevatron for supersymmetric matter has been
calculated in the framework of the minimal supergravity model in the clean
trilepton channel. Previous analyses of this channel were restricted to scalar
masses m_0<= 1 TeV. We extend the analysis to large values of scalar masses
m_0\sim 3.5 TeV. This includes the compelling hyperbolic branch/focus point
(HB/FP) region, where the superpotential \mu parameter becomes small. In this
region, assuming a 5\sigma (3\sigma) signal with 10 (25) fb^{-1} of integrated
luminosity, the Tevatron reach in the trilepton channel extends up to
m_{1/2}\sim 190 (270) GeV independent of \tan\beta . This corresponds to a
reach in terms of the gluino mass of m_{\tg}\sim 575 (750) GeV.Comment: 11 page latex file including 6 EPS figures; several typos corrected
and references adde
Triviality and the (Supersymmetric) See-Saw
For the D=5 Majorana neutrino mass operator to have a see-saw ultraviolet
completion that is viable up to the Planck scale, the see-saw scale is bounded
above due to triviality limits on the see-saw couplings. For supersymmetric
see-saw models, with realistic neutrino mass textures, we compare constraints
on the see-saw scale from triviality bounds, with those arising from
experimental limits on induced charged-lepton flavour violation, for both the
CMSSM and for models with split supersymmetry.Comment: 27 pages, 7 figures, references adde
Linear Collider Capabilities for Supersymmetry in Dark Matter Allowed Regions of the mSUGRA Model
Recent comparisons of minimal supergravity (mSUGRA) model predictions with
WMAP measurements of the neutralino relic density point to preferred regions of
model parameter space. We investigate the reach of linear colliders (LC) with
and 1 TeV for SUSY in the framework of the mSUGRA model. We find
that LCs can cover the entire stau co-annihilation region provided \tan\beta
\alt 30. In the hyperbolic branch/focus point (HB/FP) region of parameter
space, specialized cuts are suggested to increase the reach in this important
``dark matter allowed'' area. In the case of the HB/FP region, the reach of a
LC extends well past the reach of the CERN LHC. We examine a case study in the
HB/FP region, and show that the MSSM parameters and can be
sufficiently well-measured to demonstrate that one would indeed be in the HB/FP
region, where the lightest chargino and neutralino have a substantial higgsino
component.Comment: 29 pages, 15 EPS figures; updated version slightly modified to
conform with published versio
Neutralino Decays at the CERN LHC
We study the distribution of lepton pairs from the second lightest neutralino
decay \tchi^0_2\to\tchi^0_1 l^+l^-. This decay mode is important to measure the
mass difference between \tchi^0_2 and the lightest neutralino \tchi^0_1, which
helps to determine the parameters of the minimal supersymmetric standard model
at the CERN LHC. We found that the decay distribution strongly depends on the
values of underlying MSSM parameters. For some extreme cases, the amplitude
near the end point of the lepton invariant mass distribution can be suppressed
so strongly that one needs the information of the whole m_{ll} distribution to
extract m_{\tchi^0_2}-m_{\tchi^0_1}. On the other hand, if systematic errors on
the acceptance can be controlled, this distribution can be used to constrain
slepton masses and the Z\tchi^0_2\tchi^0_1 coupling. Measurements of the
velocity distribution of \tchi^0_2 from samples near the end point of the
m_{ll} distribution, and of the asymmetry of the p_T of leptons, would be
useful to reduce the systematic errors.Comment: 23 pages, latex2e, 9 figures, minor change, accepted to PR
Reconciling Neutralino Relic Density with Yukawa Unified Supersymmetric Models
Supersymmetric grand unified models based on the gauge group SO(10) are
especially attractive in light of recent data on neutrino masses. The simplest
SO(10) SUSY GUT models predict unification of third generation Yukawa couplings
in addition to the usual gauge coupling unification. Recent surveys of Yukawa
unified SUSY GUT models predict an inverted scalar mass hierarchy in the
spectrum of sparticle masses if the superpotential mu term is positive. In
general, such models tend to predict an overabundance of dark matter in the
universe. We survey several solutions to the dark matter problem in Yukawa
unified supersymmetric models. One solution-- lowering the GUT scale mass value
of first and second generation scalars-- leads to u_R and c_R squark masses in
the 90-120 GeV regime, which should be accessible to Fermilab Tevatron
experiments. We also examine relaxing gaugino mass universality which may solve
the relic density problem by having neutralino annihilations via the Z or h
resonances, or by having a wino-like LSP.Comment: 21 page file plus 9 figures; updated version to coincide with
published versio
Markov Chain Monte Carlo Exploration of Minimal Supergravity with Implications for Dark Matter
We explore the full parameter space of Minimal Supergravity (mSUGRA),
allowing all four continuous parameters (the scalar mass m_0, the gaugino mass
m_1/2, the trilinear coupling A_0, and the ratio of Higgs vacuum expectation
values tan beta) to vary freely. We apply current accelerator constraints on
sparticle and Higgs masses, and on the b -> s gamma branching ratio, and
discuss the impact of the constraints on g_mu-2. To study dark matter, we apply
the WMAP constraint on the cold dark matter density. We develop Markov Chain
Monte Carlo (MCMC) techniques to explore the parameter regions consistent with
WMAP, finding them to be considerably superior to previously used methods for
exploring supersymmetric parameter spaces. Finally, we study the reach of
current and future direct detection experiments in light of the WMAP
constraint.Comment: 16 pages, 4 figure
Accidental Supersymmetric Dark Matter and Baryogenesis
We show that "accidental" supersymmetry is a beyond-the-Standard Model
framework that naturally accommodates a thermal relic dark matter candidate and
successful electroweak baryogenesis, including the needed strongly first-order
character of the electroweak phase transition. We study the phenomenology of
this setup from the standpoint of both dark matter and baryogenesis. For
energies around the electroweak phase transition temperature, the low-energy
effective theory is similar to the MSSM with light super-partners of the
third-generation quarks and of the Higgs and gauge bosons. We calculate the
dark matter relic abundance and the baryon asymmetry across the accidental
supersymmetry parameter space, including resonant and non-resonant CP-violating
sources. We find that there are regions of parameter space producing both the
observed value of the baryon asymmetry and a dark matter candidate with the
correct relic density and conforming to present-day constraints from dark
matter searches. This scenario makes sharp predictions for the particle
spectrum, predicting a lightest neutralino mass between 200 and 500 GeV, with
all charginos and neutralinos within less than a factor 2 of the lightest
neutralino mass and the heavy Higgs sector within 20-25% of that mass, making
it an interesting target for collider searches. In addition, we demonstrate
that successful accidental supersymmetric dark matter and baryogenesis will be
conclusively tested with improvements smaller than one order of magnitude to
the current performance of electron electric dipole moment searches and of
direct dark matter searches, as well as with IceCube plus Deep Core neutrino
telescope data.Comment: 36 pages, 10 figure
Perspectives for the detection and measurement of Supersymmetry in the focus point region of mSUGRA models with the ATLAS detector at LHC
This paper discusses the ATLAS potential to study Supersymmetry for the
"Focus-Point" region of the parameter space of mSUGRA models. The potential to
discovery a deviation from Standard Model expectations with the first few
of LHC data was studied using the parametrized simulation of the
ATLAS detector. Several signatures were considered, involving hard jets, large
missing energy, and either -tagged jets, opposite-sign isolated electron or
muon pairs, or top quarks reconstructed exploiting their fully hadronic decays.
With only 1 of data each of these signatures may allow to observe
an excess of events over Standard Model expectation with a statistical
significance exceeding 5 standard deviations. An analytical expression was
derived for the shape of the distribution of the dilepton invariant mass
arising from the three-body leptonic decay of the neutralinos under the
hypothesis of heavy scalars, which is appropriate for the focus-point scenario.
The resulting function was used to fit the distribution of the dilepton
invariant mass obtained with simulated LHC data, and to extract the value of
two kinematic endpoints measuring the and
the mass differences. This information was
used to constrain the MSSM parameter space compatible with the data
Relating the CMSSM and SUGRA models with GUT scale and Super-GUT scale Supersymmetry Breaking
While the constrained minimal supersymmetric standard model (CMSSM) with
universal gaugino masses, m_{1/2}, scalar masses, m_0, and A-terms, A_0,
defined at some high energy scale (usually taken to be the GUT scale) is
motivated by general features of supergravity models, it does not carry all of
the constraints imposed by minimal supergravity (mSUGRA). In particular, the
CMSSM does not impose a relation between the trilinear and bilinear soft
supersymmetry breaking terms, B_0 = A_0 - m_0, nor does it impose the relation
between the soft scalar masses and the gravitino mass, m_0 = m_{3/2}. As a
consequence, tan(\beta) is computed given values of the other CMSSM input
parameters. By considering a Giudice-Masiero (GM) extension to mSUGRA, one can
introduce new parameters to the K\"ahler potential which are associated with
the Higgs sector and recover many of the standard CMSSM predictions. However,
depending on the value of A_0, one may have a gravitino or a neutralino dark
matter candidate. We also consider the consequences of imposing the
universality conditions above the GUT scale. This GM extension provides a
natural UV completion for the CMSSM.Comment: 16 pages, 11 figures; added erratum correcting several equations and
results in Sec.2, Sec.3 and 4 remain unaffected and conclusions unchange
Updated Reach of the CERN LHC and Constraints from Relic Density, b->s gamma and a(mu) in the mSUGRA Model
{We present an updated assessment of the reach of the CERN LHC pp collider
for supersymmetric matter in the context of the minimal supergravity (mSUGRA)
model. In addition to previously examined channels, we also include signals
with an isolated photon or with a leptonically decaying Z boson. For an
integrated luminosity of 100 fb^{-1}, values of m_{1/2}\sim 1400 GeV can be
probed for small m_0, corresponding to a gluino mass of m_{\tg}\sim 3 TeV. For
large m_0, in the hyperbolic branch/focus point region, m_{1/2}\sim 700 GeV can
be probed, corresponding to m_{\tg}\sim 1800 GeV. We also map out parameter
space regions preferred by the measured values of the dark matter relic
density, the b\to s\gamma decay rate, and the muon anomalous magnetic moment
a_\mu, and discuss how SUSY might reveal itself in these regions. We find the
CERN LHC can probe the entire stau co-annihilation region and also most of the
heavy Higgs annihilation funnel allowed by WMAP data, except for some range of
large m_0 and m_{1/2} if \tan\beta \agt 50.Comment: 22 page latex file including 10 EPS figures; bug fix in relic density
code modifies figures in co-annihilation regio
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