875 research outputs found
Searching for Dark Matter with Future Cosmic Positron Experiments
Dark matter particles annihilating in the Galactic halo can provide a flux of
positrons potentially observable in upcoming experiments, such as PAMELA and
AMS-02. We discuss the spectral features which may be associated with dark
matter annihilation in the positron spectrum and assess the prospects for
observing such features in future experiments. Although we focus on some
specific dark matter candidates, neutralinos and Kaluza-Klein states, we carry
out our study in a model independent fashion. We also revisit the positron
spectrum observed by HEAT.Comment: 19 pages, 33 figure
Accelerator Testing of the General Antiparticle Spectrometer, a Novel Approach to Indirect Dark Matter Detection
We report on recent accelerator testing of a prototype general antiparticle
spectrometer (GAPS). GAPS is a novel approach for indirect dark matter searches
that exploits the antideuterons produced in neutralino-neutralino
annihilations. GAPS captures these antideuterons into a target with the
subsequent formation of exotic atoms. These exotic atoms decay with the
emission of X-rays of precisely defined energy and a correlated pion signature
from nuclear annihilation. This signature uniquely characterizes the
antideuterons. Preliminary analysis of data from a prototype GAPS in an
antiproton beam at the KEK accelerator in Japan has confirmed the
multi-X-ray/pion star topology and indicated X-ray yields consistent with prior
expectations. Moreover our success in utilizing solid rather than gas targets
represents a significant simplification over our original approach and offers
potential gains in sensitivity through reduced dead mass in the target area.Comment: 18 pages, 9 figures, submitted to JCA
Innovator resilience potential: A process perspective of individual resilience as influenced by innovation project termination
Innovation projects fail at an astonishing rate. Yet, the negative effects of innovation project failures on the team members of these projects have been largely neglected in research streams that deal with innovation project failures. After such setbacks, it is vital to maintain or even strengthen project members’ innovative capabilities for subsequent innovation projects. For this, the concept of resilience, i.e. project members’ potential to positively adjust (or even grow) after a setback such as an innovation project failure, is fundamental. We develop the second-order construct of innovator resilience potential, which consists of six components – self-efficacy, outcome expectancy, optimism, hope, self-esteem, and risk propensity – that are important for project members’ potential of innovative functioning in innovation projects subsequent to a failure. We illustrate our theoretical findings by means of a qualitative study of a terminated large-scale innovation project, and derive implications for research and management
The fate of the B ball
The gauge-mediated SUSY-breaking (GMSB) model needs entropy production at a
relatively low temperature in the thermal history of the Universe for the
unwanted relics to be diluted. This requires a mechanism for the baryogenesis
after the entropy production, and the Affleck and Dine (AD) mechanism is a
promising candidate for it. The AD baryogenesis in the GMSB model predicts the
existence of the baryonic Q ball, that is the B ball, and this may work as the
dark matter in the Universe. In this article, we discuss the stability of the B
ball in th presence of baryon-number violating interactions. We find that the
evaporation rate increases monotonically with the B-ball charge because the
large field value inside the B ball enhances the effect of the
baryon-number-violating operators. While there are some difficulties to
evaluate the evaporation rate of the B ball, we derive the evaporation time
(lifetime) of the B ball for the mass-to-charge ratio \omega_0\gsim 100 \MEV.
The lifetime of the B ball and the distortion of the cosmic ray positron flux
and the cosmic background radiation from the B ball evaporation give
constraints on the baryon number of the B ball and the interaction, if the B
ball is the dark matter. We also discuss some unresolved properties of the B
ball.Comment: 27 pages incl 8 figs, LaTe
An Experimentalist's View of Neutrino Oscillations
Neutrinos, and primarily neutrino oscillations, have undoubtedly been one of
the most exciting topics in the field of high-energy physics over the past few
years. The existence of neutrino oscillations would require an extension of the
currently accepted description of sub-nuclear phenomena beyond the Standard
Model. Compelling evidence of new physics, which seems to be pointing towards
neutrino oscillations, is coming from the solar neutrino deficit and from the
atmospheric neutrino anomaly. More controversial effects have been observed
with artificially produced neutrinos. The present experimental status of
neutrino oscillations is reviewed, as well as the planned future experimental
programme, which, it is hoped, will solve most of the outstanding puzzles.Comment: 64 pages, 29 figures, to be published in Intern. J. Mod. Phys. A
(2001
Indirect signals from light neutralinos in supersymmetric models without gaugino mass unification
We examine indirect signals produced by neutralino self-annihilations, in the
galactic halo or inside celestial bodies, in the frame of an effective MSSM
model without gaugino-mass unification at a grand unification scale. We compare
our theoretical predictions with current experimental data of gamma-rays and
antiprotons in space and of upgoing muons at neutrino telescopes. Results are
presented for a wide range of the neutralino mass, though our discussions are
focused on light neutralinos. We find that only the antiproton signal is
potentially able to set constraints on very low-mass neutralinos, below 20 GeV.
The gamma-ray signal, both from the galactic center and from high galactic
latitudes, requires significantly steep profiles or substantial clumpiness in
order to reach detectable levels. The up-going muon signal is largely below
experimental sensitivities for the neutrino flux coming from the Sun; for the
flux from the Earth an improvement of about one order of magnitude in
experimental sensitivities (with a low energy threshold) can make accessible
neutralino masses close to O, Si and Mg nuclei masses, for which resonant
capture is operative.Comment: 17 pages, 1 tables and 5 figures, typeset with ReVTeX4. The paper may
also be found at http://www.to.infn.it/~fornengo/papers/indirect04.ps.gz or
through http://www.astroparticle.to.infn.it/. Limit from BR(Bs--> mu+ mu-)
adde
Positron Propagation and Fluxes from Neutralino Annihilation in the Halo
Supersymmetric neutralinos are one of the most promising candidates for the
dark matter in the Universe. If they exist, they should make up some fraction
of the Milky Way halo. We investigate the fluxes of positrons expected at the
Earth from neutralino annihilation in the halo. Positron propagation is treated
in a diffusion model including energy loss. The positron source function
includes contributions from both continuum and monochromatic positrons. We find
that, for a "canonical" halo model and propagation parameters, the fluxes are
generally too low to be visible. Given the large uncertainties in both
propagation and halo structure, it is however possible to obtain observable
fluxes. We also investigate the shapes of the positron spectra, including fits
to a feature indicated by the results of the HEAT experiment.Comment: 16 pages, 19 figures, uses revte
Measurement of the flux of atmospheric muons with the CAPRICE94 apparatus
A new measurement of the momentum spectra of both positive and negative muons
as function of atmospheric depth was made by the balloon-borne experiment
CAPRICE94. The data were collected during ground runs in Lynn Lake on the
19-20th of July 1994 and during the balloon flight on the 8-9th of August 1994.
We present results that cover the momentum intervals 0.3-40 GeV/c for negative
muons and 0.3-2 GeV/c for positive muons, for atmospheric depths from 3.3 to
1000 g/cm**2, respectively. Good agreement is found with previous measurements
for high momenta, while at momenta below 1 GeV/c we find latitude dependent
geomagnetic effects. These measurements are important cross-checks for the
simulations carried out to calculate the atmospheric neutrino fluxes and to
understand the observed atmospheric neutrino anomaly.Comment: 28 pages, 13 Postscript figures, uses revtex.sty, to appear in Phys.
Rev.
Kaluza-Klein Dark Matter, Electrons and Gamma Ray Telescopes
Kaluza-Klein dark matter particles can annihilate efficiently into
electron-positron pairs, providing a discrete feature (a sharp edge) in the
cosmic spectrum at an energy equal to the particle's mass (typically
several hundred GeV to one TeV). Although this feature is probably beyond the
reach of satellite or balloon-based cosmic ray experiments (those that
distinguish the charge and mass of the primary particle), gamma ray telescopes
may provide an alternative detection method. Designed to observe very
high-energy gamma-rays, ACTs also observe the diffuse flux of electron-induced
electromagnetic showers. The GLAST satellite, designed for gamma ray astronomy,
will also observe any high energy showers (several hundred GeV and above) in
its calorimeter. We show that high-significance detections of an
electron-positron feature from Kaluza-Klein dark matter annihilations are
possible with GLAST, and also with ACTs such as HESS, VERITAS or MAGIC.Comment: 10 pages, 2 figure
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