134 research outputs found
Phenomenological Consequences of Soft Leptogenesis
Soft supersymmetry breaking terms involving heavy singlet sneutrinos can be
the dominant source of leptogenesis. The relevant range of parameters is
different from standard leptogenesis: a lighter Majorana mass, M < 10^9 GeV
(allowing a solution of the gravitino problem), and smaller Yukawa couplings,
Y_N < 10^{-4}. We investigate whether the various couplings of the singlet
sneutrinos, which are constrained by the requirement of successful `soft
leptogenesis', can have observable phenomenological consequences. Specifically,
we calculate the contributions of the relevant soft supersymmetric breaking
terms to the electric dipole moments of the charged leptons and to lepton
flavor violating decays. Our result is that these contributions are small.Comment: 11 pages, 1 figure; v2: an additional contribution is considered
(modifying: fig. 1, eq. 10-13, 22) and a reference added. Conclusions
unchange
On Anisotropy of Ultra-High Energy Cosmic-Rays
We briefly summarize our study on anisotropy of Ultra-High Energy Cosmic-Rays
(UHECRs), in which we define a statistics that measures the correlation between
UHECRs and Large Scale Structure (LSS). We also comment here on recently
published paper by Koers and Tinyakov that compared our statistics to improved
KS statistics.Comment: 3 pages, 2 figures, proceedings of PANIC 2008. v2: version match
publication in Nuclear Physics
A Machine Vision System for Evaluation of Planter Seed Spatial Distribution
Rosana G. Moreira, Editor-in-Chief; Texas A&M UniversityThis is a Technical Paper from International Commission of Agricultural Engineering (CIGR, Commission Internationale du Genie Rural) E-Journal Volume 4 (2002): V. Alchanatis, Y. Kashti, and R. Brikman. A Machine Vision System for Evaluation of Planter Seed Spatial Distribution
Leptogenesis from Supersymmetry Breaking
We show that soft supersymmetry breaking terms involving the heavy sneutrinos
can lead to sneutrino-antisneutrino mixing and to new sources of CP violation,
which are present even if a single generation is considered. These terms are
naturally present in supersymmetric versions of leptogenesis scenarios, and
they induce indirect CP violation in the decays of the heavy sneutrinos,
eventually generating a baryon asymmetry. This new contribution can be
comparable to or even dominate over the asymmetry produced in traditional
leptogenesis scenarios.Comment: 4 pages; An improved discussion of the relevant numerical range of
the soft breaking terms (in agreement with hep-ph/0308031
DeepCut: Unsupervised Segmentation using Graph Neural Networks Clustering
Image segmentation is a fundamental task in computer vision. Data annotation
for training supervised methods can be labor-intensive, motivating unsupervised
methods. Current approaches often rely on extracting deep features from
pre-trained networks to construct a graph, and classical clustering methods
like k-means and normalized-cuts are then applied as a post-processing step.
However, this approach reduces the high-dimensional information encoded in the
features to pair-wise scalar affinities. To address this limitation, this study
introduces a lightweight Graph Neural Network (GNN) to replace classical
clustering methods while optimizing for the same clustering objective function.
Unlike existing methods, our GNN takes both the pair-wise affinities between
local image features and the raw features as input. This direct connection
between the raw features and the clustering objective enables us to implicitly
perform classification of the clusters between different graphs, resulting in
part semantic segmentation without the need for additional post-processing
steps. We demonstrate how classical clustering objectives can be formulated as
self-supervised loss functions for training an image segmentation GNN.
Furthermore, we employ the Correlation-Clustering (CC) objective to perform
clustering without defining the number of clusters, allowing for k-less
clustering. We apply the proposed method for object localization, segmentation,
and semantic part segmentation tasks, surpassing state-of-the-art performance
on multiple benchmarks
New Ways to Soft Leptogenesis
Soft supersymmetry breaking terms involving heavy singlet sneutrinos provide
new sources of lepton number violation and of CP violation. In addition to the
CP violation in mixing, investigated previously, we find that `soft
leptogenesis' can be generated by CP violation in decay and in the interference
of mixing and decay. These additional ways to leptogenesis can be significant
for a singlet neutrino Majorana mass that is not much larger than the
supersymmetry breaking scale, . In contrast to CP violation
in mixing, for some of these new contributions the sneutrino oscillation rate
can be much faster than the decay rate, so that the bilinear scalar term need
not be smaller than its natural scale.Comment: 18 pages, 3 figure
Probing Cosmic Accelerators Using VHE Gamma Rays and UHE cosmic rays
The -ray emission observed in several classes of Galactic and
extragalactic astrophysical sources appears to be linked to accreting black
holes and rotational powered neutron stars. These systems are prodigious cosmic
accelerators, and are also potential sources of the UHE cosmic rays detected by
several experiments and VHE neutrinos. We review a recent progress in our
understanding of these objects, and demonstrate how recent and future
observations can be employed to probe the conditions in the sources.Comment: Proc. PANIC08 (invited
Neutrinos from Decaying Muons, Pions, Kaons and Neutrons in Gamma Ray Bursts
In the internal shock model of gamma ray bursts ultrahigh energy muons,
pions, neutrons and kaons are likely to be produced in the interactions of
shock accelerated relativistic protons with low energy photons (KeV-MeV). These
particles subsequently decay to high energy neutrinos/antineutrinos and other
secondaries.
In the high internal magnetic fields of gamma ray bursts, the ultrahigh
energy charged particles (, , ) lose energy significantly
due to synchrotron radiations before decaying into secondary high energy
neutrinos and antineutrinos. The relativistic neutrons decay to high energy
antineutrinos, protons and electrons. We have calculated the total neutrino
flux (neutrino and antineutrino) considering the decay channels of ultrahigh
energy muons, pions, neutrons and kaons. We have shown that the total neutrino
flux generated in neutron decay can be higher than that produced in and
decay. The charged kaons being heavier than pions, lose energy slowly
and their secondary total neutrino flux is more than that from muons and pions
at very high energy. Our detailed calculations on secondary particle production
in interactions give the total neutrino fluxes and their flavour
ratios expected on earth. Depending on the values of the parameters
(luminosity, Lorentz factor, variability time, spectral indices and break
energy in the photon spectrum) of a gamma ray burst the contributions to the
total neutrino flux from the decay of different particles (muon, pion, neutron
and kaon) may vary and they would also be reflected on the neutrino flavour
ratios.Comment: 18 pages, 6 figures, version accepted for publication in
Astroparticle Physic
Centaurus A as a point source of Ultra-High Energy Cosmic Rays
We probe the possibility that Centaurus A (Cen A) is a point source of
ultra-high energy cosmic rays (UHECR) observed by PAO, through the statistical
analysis of the arrival direction distribution. For this purpose, we set up the
Cen A dominance model for the UHECR sources, in which Cen A contributes the
fraction of the whole UHECR with energy above
and the isotropic background contributes the
remaining fraction. The effect of the intergalactic magnetic
fields on the bending of the trajectory of Cen A originated UHECR is
parameterized by the gaussian smearing angle . Using the
correlational angular distance distribution (CADD), we identify the excess of
UHECR in the Cen A direction and fit the CADD of the observed PAO data by
varying two parameters and of the Cen A dominance model.
The best-fit parameter values are (The corresponding Cen
A fraction observed at PAO is , that is, about 10 out
of 69 UHECR.) and with the maximum probability . Considering the uncertainty concerning the assumption of isotropic
background in the Cen A dominance model, we extend the viable parameter ranges
to the band, and
. This result supports the existence
of a point source extended by the intergalactic magnetic fields in the
direction of Cen A. If Cen A is actually the source responsible for the
observed excess of UHECR, the average deflection angle of the excess UHECR
implies the order of intergalactic magnetic field in the
vicinity of Cen A.Comment: 12 pages, 7 figure
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