73 research outputs found
Same-sign top quarks as signature of light stops at the CERN LHC
We present a new method to search for a light scalar top with
m_{\tilde{t}_1}\lsim m_t, decaying dominantly into a c-jet and the lightest
neutralino, at the LHC. The principal idea is to exploit the Majorana nature of
the gluino, leading to same-sign top quarks in events of gluino-pair production
followed by gluino decays into top and stop. The resulting signature is 2
b-jets plus 2 same-sign leptons plus additional jets and missing energy. We
perform a Monte Carlo simulation for a benchmark scenario, which is in
agreement with the recent WMAP bound on the relic density of dark matter, and
demonstrate that for m_{\tilde{g}}\lsim 900 GeV and
the signal can be extracted from the background.
Moreover, we discuss the determination of the stop and gluino masses from the
shape of invariant-mass distributions. The derivation of the shape formulae is
also given.Comment: 20 pages, 6 figures, minor changes; version to appear in PR
Same-sign top quarks as signature of light stops
We present a new method to search for a light scalar top (stop), decaying
dominantly into , at the LHC. The principal idea is to exploit
the Majorana nature of the gluino, leading to same-sign top quarks in events of
gluino pair production followed by gluino decays into top and stop. We
demonstrate the reach of our method in terms of the gluino mass and the
stop-neutralino mass difference.Comment: 4 pages, 1 figure, to appear in Proceedings of SUSY06, the 14th
International Conference on Supersymmetry and the Unification of Fundamental
Interactions, UC Irvine, California, 12-17 June 200
Antideuteron Limits on Decaying Dark Matter with a Tuned Formation Model
We investigate the production of antideuterons from decaying dark matter,
using gravitinos in supersymmetric models with trilinear R-parity violating
(RPV) operators as an example. The model used for antideuteron formation is
shown to induce large uncertainties in the predicted flux, comparable to
uncertainties from cosmic-ray propagation models. We improve on the formation
model by tuning hadronization and coalesence parameters in Monte Carlo
simulations to better reproduce the hadron spectra relevant for antideuteron
production. In light of current bounds on fluxes and future prospects from the
AMS-II and GAPS experiments we set limits on RPV couplings as a function of the
gravitino mass.Comment: Updated; corresponds to version published in Phys. Rev. D. 14 pages,
9 figure
An Alternative Formation Model for Antideuterons from Dark Matter
Antideuterons are a potential messenger for dark matter annihilation or decay
in our own galaxy, with very low backgrounds expected from astrophysical
processes. The standard coalescence model of antideuteron formation, while
simple to implement, is shown to be under considerable strain by recent data
from the LHC. We suggest a new empirically based model, with only one free
parameter, which is better able to cope with these data, and we explore the
consequences of the model for dark matter searches.Comment: 19 pages, 15 figures, C++ code with parametrised cross sections can
be found in the ancillary folder, v2 fixes important missing reference
Mass Determination in Cascade Decays Using Shape Formulas
In SUSY scenarios with invisible LSP, sparticle masses can be determined from
fits to the endpoints of invariant mass distributions. Here we discuss possible
improvements by using the shapes of the distributions. Positive results are
found for multiple-minima situations and for mass regions where the endpoints
do not contain sufficient information to obtain the masses.Comment: to appear in Proceedings of SUSY06, the 14th International Conference
on Supersymmetry and the Unification of Fundamental Interactions, UC Irvine,
California, 12-17 June 200
Cosmic Ray Signatures from Decaying Gravitino Dark Matter
We study the charged cosmic rays arising from the slow decay of gravitino
dark matter within supersymmetric scenarios with trilinear R-parity violation.
It is shown that operators of the LLE type can very well account for the recent
anomalies in cosmic ray electron and positron data reported by PAMELA, ATIC and
Fermi LAT, without violating any other bounds. This scenario will soon be
tested by the Fermi LAT data on diffuse gamma ray emission.Comment: To appear in the proceedings of EPS-HEP 2009, Krakow, Polan
Long lived charginos in Natural SUSY?
Supersymmetric models with a small neutralino-chargino mass difference, and
as a result metastable charginos, have been a popular topic of investigation in
collider phenomenology, e.g. in anomaly-mediated models of supersymmetry
breaking. Recently, the absence of any supersymmetric signal at the 8 TeV LHC
data has led to significant interest in the so-called Natural SUSY models with
light higgsinos. These models also have a naturally small neutralino-chargino
mass difference. However, we show here that when relevant indirect constraints
from results at the LHC and elsewhere are applied, this possibility is heavily
constrained within the Minimal Supersymmetric Standard Model (MSSM): massive
metastable higgsinos are not a signature of Natural SUSY.Comment: Extended discussion, updated references, matches version to appear in
JHE
Mass ambiguities in cascade decays
We review the use of invariant mass distributions in cascade decays to
measure the masses of New Physics (NP) particles in scenarios where the final
NP cascade particle is invisible. We extend earlier work by exploring further
the problem of multiple solutions for the masses.Comment: 4 pages, 4 figures, to appear in the proceedings of the XXXIII
International Conference on High Energy Physics (ICHEP'06), July 26 - August
2 2006, Mosco
Status of cosmic-ray antideuteron searches
The precise measurement of cosmic-ray antiparticles serves as important means
for identifying the nature of dark matter. Recent years showed that identifying
the nature of dark matter with cosmic-ray positrons and higher energy
antiprotons is difficult, and has lead to a significantly increased interest in
cosmic-ray antideuteron searches. Antideuterons may also be generated in dark
matter annihilations or decays, offering a potential breakthrough in unexplored
phase space for dark matter. Low-energy antideuterons are an important approach
because the flux from dark matter interactions exceeds the background flux by
more than two orders of magnitude in the low-energy range for a wide variety of
models. This review is based on the "dbar14 - dedicated cosmic-ray antideuteron
workshop", which brought together theorists and experimentalists in the field
to discuss the current status, perspectives, and challenges for cosmic-ray
antideuteron searches and discusses the motivation for antideuteron searches,
the theoretical and experimental uncertainties of antideuteron production and
propagation in our Galaxy, as well as give an experimental cosmic-ray
antideuteron search status update. This report is a condensed summary of the
article "Review of the theoretical and experimental status of dark matter
identification with cosmic-ray antideuteron" (arXiv:1505.07785).Comment: 9 pages, 4 figures, ICRC 2015 proceeding
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