69 research outputs found
PAMELA, DAMA, INTEGRAL and Signatures of Metastable Excited WIMPs
Models of dark matter with ~ GeV scale force mediators provide attractive
explanations of many high energy anomalies, including PAMELA, ATIC, and the
WMAP haze. At the same time, by exploiting the ~ MeV scale excited states that
are automatically present in such theories, these models naturally explain the
DAMA/LIBRA and INTEGRAL signals through the inelastic dark matter (iDM) and
exciting dark matter (XDM) scenarios, respectively. Interestingly, with only
weak kinetic mixing to hypercharge to mediate decays, the lifetime of excited
states with delta < 2 m_e is longer than the age of the universe. The
fractional relic abundance of these excited states depends on the temperature
of kinetic decoupling, but can be appreciable. There could easily be other
mechanisms for rapid decay, but the consequences of such long-lived states are
intriguing. We find that CDMS constrains the fractional relic population of
~100 keV states to be <~ 10^-2, for a 1 TeV WIMP with sigma_n = 10^-40 cm^2.
Upcoming searches at CDMS, as well as xenon, silicon, and argon targets, can
push this limit significantly lower. We also consider the possibility that the
DAMA excitation occurs from a metastable state into the XDM state, which decays
via e+e- emission, which allows lighter states to explain the INTEGRAL signal
due to the small kinetic energies required. Such models yield dramatic signals
from down-scattering, with spectra peaking at high energies, sometimes as high
as ~1 MeV, well outside the usual search windows. Such signals would be visible
at future Ar and Si experiments, and may be visible at Ge and Xe experiments.
We also consider other XDM models involving ~ 500 keV metastable states, and
find they can allow lighter WIMPs to explain INTEGRAL as well.Comment: 22 pages, 7 figure
Baryogenesis, Electric Dipole Moments and Dark Matter in the MSSM
We study the implications for electroweak baryogenesis (EWB) within the
minimal supersymmetric Standard Model (MSSM) of present and future searches for
the permanent electric dipole moment (EDM) of the electron, for neutralino dark
matter, and for supersymmetric particles at high energy colliders. We show that
there exist regions of the MSSM parameter space that are consistent with both
present two-loop EDM limits and the relic density and that allow for successful
EWB through resonant chargino and neutralino processes at the electroweak phase
transition. We also show that under certain conditions the lightest neutralino
may be simultaneously responsible for both the baryon asymmetry and relic
density. We give present constraints on chargino/neutralino-induced EWB implied
by the flux of energetic neutrinos from the Sun, the prospective constraints
from future neutrino telescopes and ton-sized direct detection experiments, and
the possible signatures at the Large Hadron Collider and International Linear
Collider.Comment: 32 pages, 10 figures; version to appear on JHE
Direct detection of neutralino dark matter in supergravity
The direct detection of neutralino dark matter is analysed in general
supergravity scenarios, where non-universal soft scalar and gaugino masses can
be present. In particular, the theoretical predictions for the
neutralino-nucleon cross section are studied and compared with the sensitivity
of dark matter detectors. We take into account the most recent astrophysical
and experimental constraints on the parameter space, including the current
limit on B(Bs-> mu+ mu-). The latter puts severe limitations on the dark matter
scattering cross section, ruling out most of the regions that would be within
the reach of present experiments. We show how this constraint can be softened
with the help of appropriate choices of non-universal parameters which increase
the Higgsino composition of the lightest neutralino and minimise the chargino
contribution to the b->s transition.Comment: 27 pages, 22 figure
Model Independent Approach to Focus Point Supersymmetry: from Dark Matter to Collider Searches
The focus point region of supersymmetric models is compelling in that it
simultaneously features low fine-tuning, provides a decoupling solution to the
SUSY flavor and CP problems, suppresses proton decay rates and can accommodate
the WMAP measured cold dark matter (DM) relic density through a mixed
bino-higgsino dark matter particle. We present the focus point region in terms
of a weak scale parameterization, which allows for a relatively model
independent compilation of phenomenological constraints and prospects. We
present direct and indirect neutralino dark matter detection rates for two
different halo density profiles, and show that prospects for direct DM
detection and indirect detection via neutrino telescopes such as IceCube and
anti-deuteron searches by GAPS are especially promising. We also present LHC
reach prospects via gluino and squark cascade decay searches, and also via
clean trilepton signatures arising from chargino-neutralino production. Both
methods provide a reach out to m_{\tg}\sim 1.7 TeV. At a TeV-scale linear
e^+e^- collider (LC), the maximal reach is attained in the \tz_1\tz_2 or
\tz_1\tz_3 channels. In the DM allowed region of parameter space, a
\sqrt{s}=0.5 TeV LC has a reach which is comparable to that of the LHC.
However, the reach of a 1 TeV LC extends out to m_{\tg}\sim 3.5 TeV.Comment: 34 pages plus 36 eps figure
Barbed suture vs conventional tenorrhaphy: biomechanical analysis in an animal model.
BACKGROUND: The advantages of barbed suture for tendon repair could be to eliminate the need for a knot and to better distribute the load throughout the tendon so as to reduce the deformation at the repair site. The purpose of this study was to evaluate the breaking force and the repair site deformation of a new barbed tenorrhaphy technique in an animal model. MATERIALS AND METHODS: Sixty porcine flexor tendons were divided randomly into three groups and repaired with one of the following techniques: a new 4-strand barbed technique using 2/0 polypropylene Quillā¢ SRS or 2/0 polydioxanone Quillā¢ SRS and a modified Kessler technique using 3/0 prolene. All tendons underwent mechanical testing to assess the 2-mm gap formation force, the breaking force and the mode of failure. The percentage change in tendon cross-sectional area before and after repair was calculated. RESULTS: The two-sample Student t-test demonstrated a significant increase in 2-mm gap formation force and in breaking force with barbed sutures, independently from suture material, when compared to traditional Kessler suture. Concerning the tendon profile, we registered less bunching at the repair site in the two barbed groups compared with the Kessler group. CONCLUSIONS: This study confirms the promising results achieved in previous ex vivo studies about the use of barbed suture in flexor tendon repair. In our animal model, tenorrhaphy with Quillā¢ SRS suture guarantees a breaking force of repair that exceeds the 40-50 N suggested as sufficient to initiate early active motion, and a smoother profile at the repair site. LEVEL OF EVIDENCE: Not applicable
Theoretical predictions for the direct detection of neutralino dark matter in the NMSSM
We analyse the direct detection of neutralino dark matter in the framework of
the Next-to-Minimal Supersymmetric Standard Model. After performing a detailed
analysis of the parameter space, taking into account all the available
constraints from LEPII, we compute the neutralino-nucleon cross section, and
compare the results with the sensitivity of detectors. We find that sizable
values for the detection cross section, within the reach of dark matter
detectors, are attainable in this framework. For example, neutralino-proton
cross sections compatible with the sensitivity of present experiments can be
obtained due to the exchange of very light Higgses with m_{h_1^0}\lsim 70
GeV. Such Higgses have a significant singlet composition, thus escaping
detection and being in agreement with accelerator data. The lightest neutralino
in these cases exhibits a large singlino-Higgsino composition, and a mass in
the range 50\lsim m_{\tilde\chi_1^0}\lsim 100 GeV.Comment: Final version to appear in JHEP. References added. LaTeX, 53 pages,
23 figure
Mixed Higgsino Dark Matter from a Large SU(2) Gaugino Mass
We observe that in SUSY models with non-universal GUT scale gaugino mass
parameters, raising the GUT scale SU(2) gaugino mass |M_2| from its unified
value results in a smaller value of -m_{H_u}^2 at the weak scale. By the
electroweak symmetry breaking conditions, this implies a reduced value of \mu^2
{\it vis \`a vis} models with gaugino mass unification. The lightest neutralino
can then be mixed Higgsino dark matter with a relic density in agreement with
the measured abundance of cold dark matter (DM). We explore the phenomenology
of this high |M_2| DM model. The spectrum is characterized by a very large wino
mass and a concomitantly large splitting between left- and right- sfermion
masses. In addition, the lighter chargino and three light neutralinos are
relatively light with substantial higgsino components. The higgsino content of
the LSP implies large rates for direct detection of neutralino dark matter, and
enhanced rates for its indirect detection relative to mSUGRA. We find that
experiments at the LHC should be able to discover SUSY over the portion of
parameter space where m_{\tg} \alt 2350-2750 ~GeV, depending on the squark
mass, while a 1 TeV electron-positron collider has a reach comparable to that
of the LHC. The dilepton mass spectrum in multi-jet + \ell^+\ell^- + \eslt
events at the LHC will likely show more than one mass edge, while its shape
should provide indirect evidence for the large higgsino content of the decaying
neutralinos.Comment: 36 pages with 26 eps figure
Mixed Wino Dark Matter: Consequences for Direct, Indirect and Collider Detection
In supersymmetric models with gravity-mediated SUSY breaking and gaugino mass
unification, the predicted relic abundance of neutralinos usually exceeds the
strict limits imposed by the WMAP collaboration. One way to obtain the correct
relic abundance is to abandon gaugino mass universality and allow a mixed
wino-bino lightest SUSY particle (LSP). The enhanced annihilation and
scattering cross sections of mixed wino dark matter (MWDM) compared to bino
dark matter lead to enhanced rates for direct dark matter detection, as well as
for indirect detection at neutrino telescopes and for detection of dark matter
annihilation products in the galactic halo. For collider experiments, MWDM
leads to a reduced but significant mass gap between the lightest neutralinos so
that chi_2^0 two-body decay modes are usually closed. This means that dilepton
mass edges-- the starting point for cascade decay reconstruction at the CERN
LHC-- should be accessible over almost all of parameter space. Measurement of
the m_{\tz_2}-m_{\tz_1} mass gap at LHC plus various sparticle masses and cross
sections as a function of beam polarization at the International Linear
Collider (ILC) would pinpoint MWDM as the dominant component of dark matter in
the universe.Comment: 29 pages including 19 eps figure
Mixed Higgsino Dark Matter from a Reduced SU(3) Gaugino Mass: Consequences for Dark Matter and Collider Searches
In gravity-mediated SUSY breaking models with non-universal gaugino masses,
lowering the SU(3) gaugino mass |M_3| leads to a reduction in the squark and
gluino masses. Lower third generation squark masses, in turn, diminish the
effect of a large top quark Yukawa coupling in the running of the higgs mass
parameter m_{H_u}^2, leading to a reduction in the magnitude of the
superpotential mu parameter (relative to M_1 and M_2). A low | mu | parameter
gives rise to mixed higgsino dark matter (MHDM), which can efficiently
annihilate in the early universe to give a dark matter relic density in accord
with WMAP measurements. We explore the phenomenology of the low |M_3| scenario,
and find for the case of MHDM increased rates for direct and indirect detection
of neutralino dark matter relative to the mSUGRA model. The sparticle mass
spectrum is characterized by relatively light gluinos, frequently with
m(gl)<<m(sq). If scalar masses are large, then gluinos can be very light, with
gl->Z_i+g loop decays dominating the gluino branching fraction. Top squarks can
be much lighter than sbottom and first/second generation squarks. The presence
of low mass higgsino-like charginos and neutralinos is expected at the CERN
LHC. The small m(Z2)-m(Z1) mass gap should give rise to a visible
opposite-sign/same flavor dilepton mass edge. At a TeV scale linear e^+e^-
collider, the region of MHDM will mean that the entire spectrum of charginos
and neutralinos are amongst the lightest sparticles, and are most likely to be
produced at observable rates, allowing for a complete reconstruction of the
gaugino-higgsino sector.Comment: 35 pages, including 26 EPS figure
Lower limit on the neutralino mass in the general MSSM
We discuss constraints on SUSY models with non-unified gaugino masses and R_P
conservation. We derive a lower bound on the neutralino mass combining the
direct limits from LEP, the indirect limits from gmuon, bsgamma, Bsmumu and the
relic density constraint from WMAP. The lightest neutralino (mneutralino=6GeV)
is found in models with a light pseudoscalar with MA<200GeV and a large value
for . Models with heavy pseudoscalars lead to mneutralino>18(29)GeV
for . We show that even a very conservative bound from the
muon anomalous magnetic moment can increase the lower bound on the neutralino
mass in models with mu<0 and/or large values of . We then examine
the potential of the Tevatron and the direct detection experiments to probe the
SUSY models with the lightest neutralinos allowed in the context of light
pseudoscalars with high . We also examine the potential of an e+e-
collider of 500GeV to produce SUSY particles in all models with neutralinos
lighter than the W. In contrast to the mSUGRA models, observation of at least
one sparticle is not always guaranteed.Comment: 37 pages, LateX, 16 figures, paper with higher resolution figures
available at
http://wwwlapp.in2p3.fr/~boudjema/papers/bound-lsp/bound-lsp.htm
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