46 research outputs found
Is the Dark Disc contribution to Dark Matter Signals important ?
Recent N-body simulations indicate that a thick disc of dark matter,
co-rotating with the stellar disc, forms in a galactic halo after a merger at a
redshift . The existence of such a dark disc component in the Milky Way
could affect dramatically dark matter signals in direct and indirect detection.
In this letter, we discuss the possible signal enhancement in connection with
the characteristics of the local velocity distributions. We argue that the
enhancement is rather mild, but some subtle effects may arise. In particular,
the annual modulation observed by DAMA becomes less constrained by other direct
detection experiments
Correlated Hierarchy, Dirac Masses and Large Mixing Angles
We introduce a new parametrization of the MNS lepton mixing matrix which
separates the hierarchical Grand Unified relations among quarks and leptons. We
argue that one large angle stems from the charged leptons, the other from the
seesaw structure of the neutral lepton mass matrix. We show how two large
mixing angles can arise naturally provided there are special requirements on
the Dirac () and Majorana () masses.
One possibility is a correlated hierarchy between them, the other is that the
Majorana mass has a specific texture; it is Dirac-like for
two of the three families.Comment: 15 pages, no fig, some refs. adde
Family Hierarchy and Large Neutrino Mixings
The recent neutrino data seem to favor two large and one small mixing angles
and a hierarchy of their squared mass differences. We discuss these within the
context of hierarchical neutrino masses. We show that this scheme suggests a
specific neutrino mass matrix with mild fine-tuning. We then present a
Froggatt-Nielsen model that reproduces this matrix
The Inert Doublet Model and Inelastic Dark Matter
The annual modulation observed by DAMA/NaI and DAMA/Libra may be interpreted
in terms of elastic or inelastic scattering of dark matter particles. In this
paper we confront these two scenarios within the framework of a very simple
extension of the Standard Model, the Inert Doublet Model (IDM). In this model
the dark matter candidate is a scalar, the lightest component of an extra Higgs
doublet. We first revisit the case for the elastic scattering of a light scalar
WIMP, M_DM~10 GeV, a scenario which requires that a fraction of events in DAMA
are channelled. Second we consider the possibility of inelastic Dark Matter
(iDM). This option is technically natural in the IDM, in the sense that the
mass splitting between the lightest and next-to-lightest neutral scalars may be
protected by a Peccei-Quinn (PQ) symmetry. We show that candidates with a mass
M_DM between ~535 GeV and ~50 TeV may reproduce the DAMA data and have a cosmic
abundance in agreement with WMAP. This range may be extended to candidates as
light as ~50 GeV if we exploit the possibility that the approximate PQ symmetry
is effectively conserved and that a primordial asymmetry in the dark sector may
survive until freeze-out.Comment: 16 pages, 7 figures. v2: minor changes and discussion on the
embedding in SO(10) added. v3: matches the published version in JCA
A reference-grade wild soybean genome
Wild relatives of crop plants are invaluable germplasm for genetic improvement. Here, Xie et al. report a reference-grade wild soybean genome and show that it can be used to identify structural variation and refine quantitative trait loci
A reference-grade wild soybean genome
Efficient crop improvement depends on the application of accurate genetic information contained in diverse germplasm resources. Here we report a reference-grade genome of wild soybean accession W05, with a final assembled genome size of 1013.2 Mb and a contig N50 of 3.3 Mb. The analytical power of the W05 genome is demonstrated by several examples. First, we identify an inversion at the locus determining seed coat color during domestication. Second, a translocation event between chromosomes 11 and 13 of some genotypes is shown to interfere with the assignment of QTLs. Third, we find a region containing copy number variations of the Kunitz trypsin inhibitor (KTI) genes. Such findings illustrate the power of this assembly in the analysis of large structural variations in soybean germplasm collections. The wild soybean genome assembly has wide applications in comparative genomic and evolutionary studies, as well as in crop breeding and improvement programs