106 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
Massive Metastable Charged (S)Particles at the LHC
This brief review deals with recent interest in the prospects of observing a
Massive Metastable Charged Particle (MMCP) at the Large Hadron Collider (LHC),
and measuring its properties there. We discuss the motivation for scenarios
with MMCPs in a phenomenological context, focusing on supersymmetric models
that allow us to explore the expected experimental signatures of MMCPs at the
LHC. We review current bounds and give estimates of the LHC reach in terms of
MMCP masses
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
Constraining the MSSM with Dark Matter indirect detection data
Recently, a claim of possible evidence for Dark Matter in data from the Fermi
LAT experiment was made by Goodenough and Hooper [8]. We test the Dark Matter
properties consistent with their claim in terms of the MSSM by a 24-dimensional
parameter scan using nested sampling, excluding all but a very small region of
the MSSM. Although this claim is very preliminary, and not made by the Fermi
LAT experiment, our scan shows a possible approach for the analysis of future
firm evidence from an indirect detection experiment, and its potential for
heavily constraining models
Discovering baryon-number violating neutralino decays at the LHC.
Recently there has been much interest in the use of single-jet mass and jet substructure to identify boosted particles decaying hadronically at the LHC. We develop these ideas to address the challenging case of a neutralino decaying to three quarks in models with baryonic violation of R parity. These decays have previously been found to be swamped by QCD backgrounds. We demonstrate for the first time that such a decay might be observed directly at the LHC with high significance, by exploiting characteristics of the scales at which its composite jet breaks up into subjets
Erratum: Alternative formation model for antideuterons from dark matter [Phys. Rev. D 91, 123536 (2015)]
© 2015 American Physical Societ
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