1,306 research outputs found
Direct Detection of Electroweak-Interacting Dark Matter
Assuming that the lightest neutral component in an SU(2)L gauge multiplet is
the main ingredient of dark matter in the universe, we calculate the elastic
scattering cross section of the dark matter with nucleon, which is an important
quantity for the direct detection experiments. When the dark matter is a real
scalar or a Majorana fermion which has only electroweak gauge interactions, the
scattering with quarks and gluon are induced through one- and two-loop quantum
processes, respectively, and both of them give rise to comparable contributions
to the elastic scattering cross section. We evaluate all of the contributions
at the leading order and find that there is an accidental cancellation among
them. As a result, the spin-independent cross section is found to be
O(10^-(46-48)) cm^2, which is far below the current experimental bounds.Comment: 19 pages, 7 figures, published versio
Slepton Oscillation at Large Hadron Collider
Measurement of Lepton-Flavor Violation (LFV) in the minimal SUSY Standard
Model (MSSM) at Large Hadron Collider (LHC) is studied based on a realistic
simulation. We consider the LFV decay of the second-lightest neutralino,
, in the case
where the flavor mixing exists in the right-handed sleptons. We scan the
parameter space of the minimal supergravity model (MSUGRA) and a more generic
model in which we take the Higgsino mass as a free parameter. We find
that the possibility of observing LFV at LHC is higher if is smaller than
the MSUGRA prediction; the LFV search at LHC can cover the parameter range
where the decay can be suppressed by the cancellation among
the diagrams for this case.Comment: 29 pages, 10 figure
Study of stop and sbottom at LHC
In supersymmetric models a gluino can decay into
through a stop or a sbottom. The decay chain produces an edge structure in the
distribution. Monte Carlo simulation studies show that the end point
and the edge height would be measured at the CERN LHC by using a sideband
subtraction technique. The stop and sbottom masses as well as their decay
branching ratios are constrained by the measurement. We study interpretations
of the measurement.Comment: 3 pages, 2 eps files, style files are included, talk at PASCOS'03,
Mumbai, India, January 3-8, 200
Probing Left-handed Slepton Flavor Mixing at Future Lepton Colliders
It has been argued in the literature that the search for the slepton
oscillation phenomenon can be a powerful probe of intergenerational mixing
between sleptons, once sleptons are found at future colliders. In this article
we estimate possible reach of future lepton colliders in probing left-handed
slepton flavor mixing, especially mixing between the first and third
generations, on which constraints imposed by other processes like are very weak. collider is suitable for this purpose, since it
can produce, if kinematically allowed, sleptons of the first generation via
t-channel, in addition to s-channel. Utilizing e^+e^- \to \tau e + 4jets + \E
signal at linear collider with integrated luminosity L=50 fb^{-1}(500
fb^{-1}) it may be possible to reach mixing angle and mass difference GeV for sneutrinos in the first and third generations at the
statistical significance of 5 \sigma.Comment: 27 pages, 6 figures. A new section added. Conclusion unchanged. To
appear in Phys. Rev.
Exact Event Rates of Lepton Flavor Violating Processes in Supersymmetric SU(5) Model
Event rates of various lepton flavor violating processes in the minimal
supersymmetric SU(5) model are calculated, using exact formulas which include
Yukawa vertices of lepton-slepton-Higgsino. We find subtlety in evaluating
event rates due to partial cancellation between diagrams. This cancellation
typically reduces the event rates significantly, and the size of the reduction
strongly depends on superparticle mass spectrum.Comment: 11pages, 8 figures. Fig.5 where the mu-e conversion rates in nuclei
was shown was incorrect due to an error in our numerical computation.It is
replaced in this corrected version. All conclusions remain unchange
A Detailed Study of the Gluino Decay into the Third Generation Squarks at the CERN LHC
In supersymmetric models a gluino can decay into tb\tilde{\chi}^{\pm}_1
through a stop or a sbottom. The decay chain produces an edge structure in the
m_{tb} distribution. Monte Carlo simulation studies show that the end point and
the edge height would be measured at the CERN LHC by using a sideband
subtraction technique. The stop and sbottom masses as well as their decay
branching ratios are constrained by the measurement. We study interpretations
of the measurement in the minimal supergravity model. We also study the gluino
decay into tb and \tilde{\chi}^{\pm}_2 as well as the influence of the stop
left-right mixing on the m_{bb} distribution of the tagged events.Comment: revtex, 20 pages in PRD format, 35 eps file
"Flavored" Electric Dipole Moments in Supersymmetric Theories
The Standard Model (SM) predictions for the hadronic electric dipole moments
(EDMs) are well far from the present experimental resolutions, thus, the EDMs
represent very clean probes of New Physics (NP) effects. Especially, within an
MSSM framework with flavor-changing (but not necessarily CP violating) soft
terms, large and potentially visible effects to the EDMs are typically
expected. In this Letter we point out that, beyond-leading-order (BLO) effects,
so far neglected in the literature, dominate over the leading-order (LO)
effects in large regions of the parameter space, hence, their inclusion in the
evaluation of the hadronic EDMs is unavoidable.Comment: 4 pages, 1 figur
WIMPonium and Boost Factors for Indirect Dark Matter Detection
We argue that WIMP dark matter can annihilate via long-lived "WIMPonium"
bound states in reasonable particle physics models of dark matter (DM).
WIMPonium bound states can occur at or near threshold leading to substantial
enhancements in the DM annihilation rate, closely related to the Sommerfeld
effect. Large "boost factor" amplifications in the annihilation rate can thus
occur without large density enhancements, possibly preferring colder less dense
objects such as dwarf galaxies as locations for indirect DM searches. The
radiative capture to and transitions among the WIMPonium states generically
lead to a rich energy spectrum of annihilation products, with many distinct
lines possible in the case of 2-body decays to or
final states. The existence of multiple radiative capture modes further
enhances the total annihilation rate, and the detection of the lines would give
direct over-determined information on the nature and self-interactions of the
DM particles.Comment: 8 pages, PDFLaTex, 5 figures, references added, published version
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