1,023 research outputs found
Neutralino Dark Matter in Minimal Supergravity: Direct Detection vs. Collider Searches
We calculate expected event rates for direct detection of relic neutralinos
as a function of parameter space of the minimal supergravity model. Numerical
results are presented for the specific case of a Ge detector. We find
significant detection rates ( events/kg/day) in regions of parameter
space most favored by constraints from and the cosmological
relic density of neutralinos. The detection rates are especially large in
regions of large , where many conventional signals for supersymmetry
at collider experiments are difficult to detect. If the parameter
is large, then there is a significant probability that the first direct
evidence for supersymmetry could come from direct detection experiments, rather
than from collider searches for sparticles.Comment: 25 page REVTEX file including 9 PS figure
Constraints on the Minimal Supergravity Model with Large
In the minimal supergravity model (mSUGRA), as the parameter
increases, the charged Higgs boson and light bottom squark masses decrease,
which can potentially increase contributions from , \tg\tb_j and
\tz_i\tb_j loops in the decay . We update a previous QCD
improved decay calculation to include in addition the effects of
gluino and neutralino loops. We find that in the mSUGRA model, loops involving
charginos also increase, and dominate over , , \tg\tq and
\tz_i\tq contributions for \tan\beta\agt 5-10. We find for large values of
that most of the parameter space of the mSUGRA model for
is ruled out due to too large a value of branching ratio . For and large , most of parameter space is
allowed, although the regions with the least fine-tuning (low and
) are ruled out due to too low a value of . We
compare the constraints from to constraints from the neutralino
relic density, and to expectations for sparticle discovery at LEP2 and the
Fermilab Tevatron colliders. Finally, we show that non-universal GUT
scale soft breaking squark mass terms can enhance gluino loop contributions to
decay rate even if these are diagonal.Comment: 14 page REVTEX file plus 6 PS figure
Possible Signals of Constrained Minimal Supersymmetry at a High Luminosity Fermilab Tevatron Collider
We study the most promising signals of Constrained Minimal Supersymmetry
detectable at a luminosity upgraded 2 TeV Fermilab Tevatron collider. Using a
full event-level Monte Carlo based on Pythia/Jetset, we simulate the trilepton
signal examining in detail the effect of constraints on the parameter space. We
also simulate the monolepton and dilepton signals, the missing E_T + jets
signal, and the signals of stop production in supersymmetry all with full
Standard Model backgrounds with realistic detector cuts. We find that large
fractions of parameter space can be probed (or eliminated if no signal is
found), but mass limits on charginos and neutralinos are not possible based
solely on the trilepton signal. Detection efficiencies depend strongly on
supersymmetry parameters beyond simply the neutralino and chargino masses;
analyses (experimental or theoretical) that do not include this will draw
misleading conclusions. Finally, we comment on how searches at LEP II will
complement searches at Fermilab.Comment: 30 pages, LaTeX, 11 figures, now uses epsf.sty. Reference in text has
been corrected; references added. Figures have been included using uufiles.
Compressed PS file with embedded figures available via anonymous ftp at
ftp://williams.physics.lsa.umich.edu/pub/preprints/UM-TH-95-14.ps.
Higgs particle detection using jets
We study the possibility of detecting the Higgs boson in the intermediate
mass range via its two jet channel. We consider only Higgs bosons produced in
association with a pair. Both and are required to
decay semileptonically to reduce the QCD background. The signal is compared
with the main background, jets, after appropriate cuts. A
sizable signal above background is seen in our simulation at the parton level.
Use of the channel with decaying to is suggested for
eliminating theoretical uncertainties in determining the signal.Comment: 10 pages, Fig.1 a,b,c,d(surve on request), plain tex, PVAM-HEP-93-
Cardiac magnetic resonance imaging in stable ischaemic heart disease
Cardiac magnetic resonance imaging (CMR) is a new robust versatile non-invasive imaging technique that can detect global and regional myocardial dysfunction, presence of myocardial ischaemia and myocardial scar tissue in one imaging session without radiation, with superb spatial and temporal resolution, inherited three-dimensional data collection and with relatively safe contrast material. The reproducibility of CMR is high which makes it possible to use this technique for serial assessment to evaluate the effect of revascularisation therapy in patients with ischaemic heart disease
Optical Absorption of an Interacting Many-Polaron Gas
The optical absorption of a many (continuum) polaron gas is derived in the
framework of a variational approach at zero temperature and weak or
intermediate electron-phonon coupling strength. We derive a compact formula for
the optical conductivity of the many-polaron system taking into account
many-body effects in the electron or hole system. Within the method presented
here, these effects are contained completely in the dynamical structure factor
of the electron or hole system. This allows to build on well-established
studies of the interacting electron gas. Based on this approach a novel feature
in the absorption spectrum of the many-polaron gas, related to the emission of
a plasmon together with a phonon, is identified. As an application and
illustration of the technique, we compare the theoretical many-polaron optical
absorption spectrum as derived in the present work with the `d-band' absorption
feature in NdCuO. Similarities are shown between the theoretically
and the experimentally derived first frequency moment of the optical absorption
of a family of differently doped NdCeCuO materials.Comment: 24 pages, 5 figures; revised and expanded versio
Two-loop Barr-Zee type Contributions to in the MSSM
We consider the contribution of a two-loop Barr-Zee type diagram to
in the minimal supersymmetric standard model (MSSM). At relatively
large , we show that the contribution of light third generation
scalar fermions and neutral CP-even Higgs, , can easily explain the
very recent BNL experimental data. In our analysis prefers negative
and positive . It is more sensitive to the chirality flipping
h^0(H^0)\wt{f}_R^*\wt{f}_L rather than chirality conserving couplings.Comment: 10 pages, 5 figures, references adde
Probing natural SUSY from stop pair production at the LHC
We consider the natural supersymmetry scenario in the framework of the
R-parity conserving minimal supersymmetric standard model (called natural MSSM)
and examine the observability of stop pair production at the LHC. We first scan
the parameters of this scenario under various experimental constraints,
including the SM-like Higgs boson mass, the indirect limits from precision
electroweak data and B-decays. Then in the allowed parameter space we study the
stop pair production at the LHC followed by the stop decay into a top quark
plus a lightest neutralino or into a bottom quark plus a chargino. From
detailed Monte Carlo simulations of the signals and backgrounds, we find the
two decay modes are complementary to each other in probing the stop pair
production, and the LHC with TeV and 100 luminosity is
capable of discovering the stop predicted in natural MSSM up to 450 GeV. If no
excess events were observed at the LHC, the 95% C.L. exclusion limits of the
stop masses can reach around 537 GeV.Comment: 19 pages, 10 figures, version accepted by JHE
Neutralino properties in the light of a further indication of an annual modulation effect in WIMP direct search
We demonstrate that the further indication of a possible annual modulation
effect, singled out by the DAMA/NaI experiment for WIMP direct detection, is
widely compatible with an interpretation in terms of a relic neutralino as the
major component of dark matter in the Universe. We discuss the supersymmetric
features of this neutralino in the Minimal Supersymmetric extension of the
Standard Model (MSSM) and their implications for searches at accelerators.Comment: 15 pages, ReVTeX, 9 figures (included as PS files
Yukawa Unification as a Window into the Soft Supersymmetry Breaking Lagrangian
We study Yukawa unification, including the effects of a physical neutrino
mass consistent with the Superkamiokande observations, in a string/-brane
inspired Pati-Salam model which allows the most general non-universal scalar
and gaugino masses, including the usual -term contributions which arise in
SO(10). We investigate how the tight constraints from rare decays such as and can provide information about the
family dependent supersymmetry breaking soft Lagrangian, for example the
trilinears associated with the second and third family. Many of our results
also apply to SO(10) to which the model approximately reduces in a limiting
case. In both models we find that Yukawa unification is perfectly viable
providing the non-universal soft masses have particular patterns. In this sense
Yukawa unification acts as a window into the soft supersymmetry breaking
Lagrangian.Comment: References added. 82 pages, 57 figures, Late
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