94 research outputs found
Decaying Hidden Dark Matter in Warped Compactification
The recent PAMELA and ATIC/Fermi/HESS experiments have observed an excess of
electrons and positrons, but not anti-protons, in the high energy cosmic rays.
To explain this result, we construct a decaying hidden dark matter model in
string theory compactification that incorporates the following two ingredients,
the hidden dark matter scenario in warped compactification and the
phenomenological proposal of hidden light particles that decay to the Standard
Model. In this model, on higher dimensional warped branes, various warped
Kaluza-Klein particles and the zero-mode of gauge field play roles of the
hidden dark matter or mediators to the Standard Model.Comment: 15 pages; v4, several clarifications added, update on Fermi/HESS
result
Astrophysical Uncertainties in the Cosmic Ray Electron and Positron Spectrum From Annihilating Dark Matter
In recent years, a number of experiments have been conducted with the goal of
studying cosmic rays at GeV to TeV energies. This is a particularly interesting
regime from the perspective of indirect dark matter detection. To draw reliable
conclusions regarding dark matter from cosmic ray measurements, however, it is
important to first understand the propagation of cosmic rays through the
magnetic and radiation fields of the Milky Way. In this paper, we constrain the
characteristics of the cosmic ray propagation model through comparison with
observational inputs, including recent data from the CREAM experiment, and use
these constraints to estimate the corresponding uncertainties in the spectrum
of cosmic ray electrons and positrons from dark matter particles annihilating
in the halo of the Milky Way.Comment: 21 pages, 9 figure
The Leptonic Higgs as a Messenger of Dark Matter
We propose that the leptonic cosmic ray signals seen by PAMELA and ATIC
result from the annihilation or decay of dark matter particles via states of a
leptonic Higgs doublet to leptons, linking cosmic ray signals of dark
matter to LHC signals of the Higgs sector. The states of the leptonic Higgs
doublet are lighter than about 200 GeV, yielding large and
event rates at the LHC. Simple models are
given for the dark matter particle and its interactions with the leptonic
Higgs, for cosmic ray signals arising from both annihilations and decays in the
galactic halo. For the case of annihilations, cosmic photon and neutrino
signals are on the verge of discovery.Comment: 34 pages, 9 figures, minor typos corrected, references adde
Pulsars as the Source of the WMAP Haze
The WMAP haze is an excess in the 22 to 93 GHz frequency bands of WMAP
extending about 10 degrees from the galactic center. We show that synchrotron
emission from electron-positron pairs injected into the interstellar medium by
the galactic population of pulsars with energies in the 1 to 100 GeV range can
explain the frequency spectrum of the WMAP haze and the drop in the average
haze power with latitude. The same spectrum of high energy electron-positron
pairs from pulsars, which gives rise to the haze, may also generate the
observed excesses in AMS, HEAT and PAMELA. We discuss the spatial morphology of
the pulsar synchrotron signal and its deviation from spherical symmetry, which
may provide an avenue to determine the pulsar contribution to the haze.Comment: 18 pages, 4 figures. Corrected errors in fig 1-3 and added discussion
of the detailed spatial morphology of the haze signa
Simplified Models for LHC New Physics Searches
This document proposes a collection of simplified models relevant to the
design of new-physics searches at the LHC and the characterization of their
results. Both ATLAS and CMS have already presented some results in terms of
simplified models, and we encourage them to continue and expand this effort,
which supplements both signature-based results and benchmark model
interpretations. A simplified model is defined by an effective Lagrangian
describing the interactions of a small number of new particles. Simplified
models can equally well be described by a small number of masses and
cross-sections. These parameters are directly related to collider physics
observables, making simplified models a particularly effective framework for
evaluating searches and a useful starting point for characterizing positive
signals of new physics. This document serves as an official summary of the
results from the "Topologies for Early LHC Searches" workshop, held at SLAC in
September of 2010, the purpose of which was to develop a set of representative
models that can be used to cover all relevant phase space in experimental
searches. Particular emphasis is placed on searches relevant for the first
~50-500 pb-1 of data and those motivated by supersymmetric models. This note
largely summarizes material posted at http://lhcnewphysics.org/, which includes
simplified model definitions, Monte Carlo material, and supporting contacts
within the theory community. We also comment on future developments that may be
useful as more data is gathered and analyzed by the experiments.Comment: 40 pages, 2 figures. This document is the official summary of results
from "Topologies for Early LHC Searches" workshop (SLAC, September 2010).
Supplementary material can be found at http://lhcnewphysics.or
Dark matter and collider phenomenology of split-UED
We explicitly show that split-universal extra dimension (split-UED), a
recently suggested extension of universal extra dimension (UED) model, can
nicely explain recent anomalies in cosmic-ray positrons and electrons observed
by PAMELA and ATIC/PPB-BETS. Kaluza-Klein (KK) dark matters mainly annihilate
into leptons because the hadronic branching fraction is highly suppressed by
large KK quark masses and the antiproton flux agrees very well with the
observation where no excess is found . The flux of cosmic gamma-rays from pion
decay is also highly suppressed and hardly detected in low energy region (E<20
GeV). Collider signatures of colored KK particles at the LHC, especially q_1
q_1 production, are studied in detail. Due to the large split in masses of KK
quarks and other particles, hard p_T jets and missing E_T are generated, which
make it possible to suppress the standard model background and discover the
signals.Comment: 32 pages, 15 figure
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