647 research outputs found
Neutrino Constraints on the Dark Matter Total Annihilation Cross Section
In the indirect detection of dark matter through its annihilation products,
the signals depend on the square of the dark matter density, making precise
knowledge of the distribution of dark matter in the Universe critical for
robust predictions. Many studies have focused on regions where the dark matter
density is greatest, e.g., the Galactic Center, as well as on the cosmic signal
arising from all halos in the Universe. We focus on the signal arising from the
whole Milky Way halo; this is less sensitive to uncertainties in the dark
matter distribution, and especially for flatter profiles, this halo signal is
larger than the cosmic signal. We illustrate this by considering a dark matter
model in which the principal annihilation products are neutrinos. Since
neutrinos are the least detectable Standard Model particles, a limit on their
flux conservatively bounds the dark matter total self-annihilation cross
section from above. By using the Milky Way halo signal, we show that previous
constraints using the cosmic signal can be improved on by 1-2 orders of
magnitude; dedicated experimental analyses should be able to improve both by an
additional 1-2 orders of magnitude.Comment: 8 pages, 4 figures; Matches version published in Phys. Rev.
Core-collapse astrophysics with a five-megaton neutrino detector
The legacy of solar neutrinos suggests that large neutrino detectors should be sited underground. However, to instead go underwater bypasses the need to move mountains, allowing much larger water Čerenkov detectors. We show that reaching a detector mass scale of ~5 Megatons, the size of the proposed Deep-TITAND, would permit observations of neutrino “mini-bursts” from supernovae in nearby galaxies on a roughly yearly basis, and we develop the immediate qualitative and quantitative consequences. Importantly, these mini-bursts would be detected over backgrounds without the need for optical evidence of the supernova, guaranteeing the beginning of time-domain MeV neutrino astronomy. The ability to identify, to the second, every core collapse in the local Universe would allow a continuous “death watch” of all stars within ~5 Mpc, making practical many previously-impossible tasks in probing rare outcomes and refining coordination of multiwavelength/multiparticle observations and analysis. These include the abilities to promptly detect otherwise-invisible prompt black hole formation, provide advance warning for supernova shock-breakout searches, define tight time windows for gravitational-wave searches, and identify “supernova impostors” by the nondetection of neutrinos. Observations of many supernovae, even with low numbers of detected neutrinos, will help answer questions about supernovae that cannot be resolved with a single high-statistics event in the Milky Way
Strong Upper Limits on Sterile Neutrino Warm Dark Matter
Sterile neutrinos are attractive dark matter candidates. Their parameter
space of mass and mixing angle has not yet been fully tested despite intensive
efforts that exploit their gravitational clustering properties and radiative
decays. We use the limits on gamma-ray line emission from the Galactic Center
region obtained with the SPI spectrometer on the INTEGRAL satellite to set new
constraints, which improve on the earlier bounds on mixing by more than two
orders of magnitude, and thus strongly restrict a wide and interesting range of
models.Comment: 4 pages, 2 figures; minor revisions, accepted for publication in
Physical Review Letter
Preliminary study and Identification of insects’ species of forensic importance in Urmia, Iran
The proper identification of the insect and arthropod species of forensic importance is the most crucial element in the field of forensic entomology. The main objective in this study was the identification of insects’ species of forensic importance in Urmia (37°, 33 N. and 45°, 4, 45 E.) and establishment of a preliminary data-base for forensic entomology purposes in Iran for the first time. A combination of various body viscera and tissues of some of vertebrates (sheep, cow, fish and hen), such as head, paunch, spleen, intestine, derma and liver was exposed in an open land on the private possession for 53 days. Ambient daily temperature (maximum and minimum) and relative humidity values were recorded; and existing keys were used for identification of different species. During the period of study, rainfall was none; average total temperature was 23.77°C; and average of mean RH or average total RH was 46.41%. Five stages of decomposition were recognized. A total of 3179 individuals were collected; belonging to 5 orders (Diptra, Coleoptera, Hymenoptera, Dermaptera and Blattaria), 11 families, 16 genera and 18 species: Psychoda sp, (Dip. Psychodidae), Calliphora vicina (Dip. Calliphoridae),Calliphora vomitoria (Dip. Calliphoridae), Lucilia sericata (Dip. Calliphoridae), Chrysoma sp. (Dip.Calliphoridae), Musca domestica (Dip. Muscidae), Muscina stabulans (Dip. Muscidae), Fannia canicularis (Dip. Fannidae), Sarcophaga haemorrhoidalis (Dip. Sarcophagidae), Sarcophaga sp. (Dip.Sarcophagidae), Wohlfartia magnifica (Dip. Sarcophagidae), Dermestes maculates (Col. Dermestidae), Necrophorus sp.(Col.Silphidae), Blatta orientalis (Blattaria . Blattidae), Vespula germanica (Hym.Vespidae), Messor caducus (Hym. Formicidae), Cataglyphis sp. (Hym. Formicidae) andForficula auricularia (Dermaptera. Forficulidae). The species of Psychoda sp, (Dip. Psychodidae), M. caducus, Cataglyphis sp. (Hym. Formicidae) and F. auricularia (Dermaptera. Forficulidae) are seldomly reported in previous researches; and they were heavily focused to tissues of animals in these studies
TeV Gamma Rays from Geminga and the Origin of the GeV Positron Excess
The Geminga pulsar has long been one of the most intriguing MeV-GeV gamma-ray
point sources. We examine the implications of the recent Milagro detection of
extended, multi-TeV gamma-ray emission from Geminga, finding that this reveals
the existence of an ancient, powerful cosmic-ray accelerator that can plausibly
account for the multi-GeV positron excess that has evaded explanation. We
explore a number of testable predictions for gamma-ray and electron/positron
experiments (up to ~100 TeV) that can confirm the first "direct" detection of a
cosmic-ray source.Comment: 4 pages and 3 figures; Minor revisions, accepted for publication in
Physical Review Letter
Best-Bet Astrophysical Neutrino Sources
Likely astrophysical sources of detectable high-energy (>> TeV) neutrinos are
considered. Based on gamma-ray emission properties, the most probable sources
of neutrinos are argued to be GRBs, blazars, microquasars, and supernova
remnants. Diffuse neutrino sources are also briefly considered.Comment: 6 pages, 2 figures, in Proc. of TeV-Particle Astrophysics II,
Madison, WI, 28-31 Aug, 200
Electronic and magnetic properties of the monolayer RuCl: A first-principles and Monte Carlo study
Recent experiments revealed that monolayer -RuCl can be obtain by
chemical exfoliation method and exfoliation or restacking of nanosheets can
manipulate the magnetic properties of the materials. In this present paper, the
electronic and magnetic properties of -RuCl monolayer are
investigated by combining first-principles calculations and Monte Carlo
simulations. From first-principles calculations, we found that the spin
configuration FM corresponds to the ground state for -RuCl,
however, the other excited zigzag oriented spin configuration has energy of 5
meV/atom higher than the ground state. Energy band gap has been obtained as
meV using PBE functionals. When spin-orbit coupling effect is taken into
account, corresponding energy gap is determined to be as meV. We also
investigate the effect of Hubbard U energy terms on the electronic band
structure of -RuCl monolayer and revealed band gap increases
approximately linear with increasing U value. Moreover, spin-spin coupling
terms (, , ) have been obtained using first principles
calculations. By benefiting from these terms, Monte Carlo simulations with
single site update Metropolis algorithm have been implemented to elucidate
magnetic properties of the considered system. Thermal variations of
magnetization, susceptibility and also specific heat curves indicate that
monolayer -RuCl exhibits a phase transition between ordered and
disordered phases at the Curie temperature K. We believe that this
study can be utilized to improve two-dimensional magnet materials
Stringent Constraint on Galactic Positron Production
The intense 0.511 MeV gamma-ray line emission from the Galactic Center
observed by INTEGRAL requires a large annihilation rate of nonrelativistic
positrons. If these positrons are injected at even mildly relativistic
energies, higher-energy gamma rays will also be produced. We calculate the
gamma-ray spectrum due to inflight annihilation and compare to the observed
diffuse Galactic gamma-ray data. Even in a simplified but conservative
treatment, we find that the positron injection energies must be
MeV, which strongly constrains models for Galactic positron production.Comment: 4 pages, 2 figures; minor revisions, accepted for publication in PR
Pyramiding multiple genes for resistance to PVY, TSWV and PMMoV in pepper using molecular markers
Pepper (Capsicum annuum L.) is one of the most important vegetables cultivated worldwide. Many pests and pathogens cause economic yield losses in pepper. Potato virus Y (PVY), Tomato spotted wilt virus (TSWV) and Pepper mild mottle virus (PMMoV) are considered among the most destructive viruses affecting pepper in the world. Because chemical treatments have limited success for managing PVY, TSWV and PMMoV, resistant varieties are considered to be the most effective means of controlling these viruses. In this study, resistance genes to these viruses were successfully transferred to the superior sweet Charleston pepper line 'Y-CAR' using molecular markers and biological assays. As a result, a new line which is resistant to PVY, TSWV and PMMoV was developed. The results also showed the applicability of a pyramiding strategy for breeding multiple virus resistance in pepper. © Verlag Eugen Ulmer KG, Stuttgart.Scientific and Technological Research Council of Turkey, TEYDEP foundation (3080171
An Unexpectedly Swift Rise in the Gamma-ray Burst Rate
The association of long gamma-ray bursts with supernovae naturally suggests
that the cosmic GRB rate should trace the star formation history. Finding
otherwise would provide important clues concerning these rare, curious
phenomena. Using a new estimate of Swift GRB energetics to construct a sample
of 36 luminous GRBs with redshifts in the range z=0-4, we find evidence of
enhanced evolution in the GRB rate, with ~4 times as many GRBs observed at z~4
than expected from star formation measurements. This direct and empirical
demonstration of needed additional evolution is a new result. It is consistent
with theoretical expectations from metallicity effects, but other causes remain
possible, and we consider them systematically.Comment: 4 pages, 4 figures; minor changes to agree with published versio
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