90 research outputs found
Measurement of the antineutrino neutral-current elastic differential cross section
arXiv:1309.7257v1 [hep-ex
Constraints on Nucleon Decay via "Invisible" Modes from the Sudbury Neutrino Observatory
Data from the Sudbury Neutrino Observatory have been used to constrain the
lifetime for nucleon decay to ``invisible'' modes, such as n -> 3 nu. The
analysis was based on a search for gamma-rays from the de-excitation of the
residual nucleus that would result from the disappearance of either a proton or
neutron from O16. A limit of tau_inv > 2 x 10^{29} years is obtained at 90%
confidence for either neutron or proton decay modes. This is about an order of
magnitude more stringent than previous constraints on invisible proton decay
modes and 400 times more stringent than similar neutron modes.Comment: Update includes missing efficiency factor (limits change by factor of
2) Submitted to Physical Review Letter
First Neutrino Observations from the Sudbury Neutrino Observatory
The first neutrino observations from the Sudbury Neutrino Observatory are
presented from preliminary analyses. Based on energy, direction and location,
the data in the region of interest appear to be dominated by 8B solar
neutrinos, detected by the charged current reaction on deuterium and elastic
scattering from electrons, with very little background. Measurements of
radioactive backgrounds indicate that the measurement of all active neutrino
types via the neutral current reaction on deuterium will be possible with small
systematic uncertainties. Quantitative results for the fluxes observed with
these reactions will be provided when further calibrations have been completed.Comment: Latex, 7 pages, 10 figures, Invited paper at Neutrino 2000
Conference, Sudbury, Canada, June 16-21, 2000 to be published in the
Proceeding
The Establishment of Genetically Engineered Canola Populations in the U.S.
Concerns regarding the commercial release of genetically engineered (GE) crops include naturalization, introgression to sexually compatible relatives and the transfer of beneficial traits to native and weedy species through hybridization. To date there have been few documented reports of escape leading some researchers to question the environmental risks of biotech products. In this study we conducted a systematic roadside survey of canola (Brassica napus) populations growing outside of cultivation in North Dakota, USA, the dominant canola growing region in the U.S. We document the presence of two escaped, transgenic genotypes, as well as non-GE canola, and provide evidence of novel combinations of transgenic forms in the wild. Our results demonstrate that feral populations are large and widespread. Moreover, flowering times of escaped populations, as well as the fertile condition of the majority of collections suggest that these populations are established and persistent outside of cultivation
Electron Antineutrino Search at the Sudbury Neutrino Observatory
Upper limits on the \nuebar flux at the Sudbury Neutrino Observatory have
been set based on the \nuebar charged-current reaction on deuterium. The
reaction produces a positron and two neutrons in coincidence. This distinctive
signature allows a search with very low background for \nuebar's from the Sun
and other potential sources. Both differential and integral limits on the
\nuebar flux have been placed in the energy range from 4 -- 14.8 MeV. For an
energy-independent \nu_e --> \nuebar conversion mechanism, the integral limit
on the flux of solar \nuebar's in the energy range from 4 -- 14.8 MeV is found
to be \Phi_\nuebar <= 3.4 x 10^4 cm^{-2} s^{-1} (90% C.L.), which corresponds
to 0.81% of the standard solar model 8B \nu_e flux of 5.05 x 10^6 cm^{-2}
s^{-1}, and is consistent with the more sensitive limit from KamLAND in the 8.3
-- 14.8 MeV range of 3.7 x 10^2 cm^{-2} s^{-1} (90% C.L.). In the energy range
from 4 -- 8 MeV, a search for \nuebar's is conducted using coincidences in
which only the two neutrons are detected. Assuming a \nuebar spectrum for the
neutron induced fission of naturally occurring elements, a flux limit of
Phi_\nuebar <= 2.0 x 10^6 cm^{-2} s^{-1}(90% C.L.) is obtained.Comment: submitted to Phys. Rev.
First Measurement of the Total Neutron Cross Section on Argon Between 100 and 800 MeV
We report the first measurement of the neutron cross section on argon in the
energy range of 100-800 MeV. The measurement was obtained with a 4.3-hour
exposure of the Mini-CAPTAIN detector to the WNR/LANSCE beam at LANL. The total
cross section is measured from the attenuation coefficient of the neutron flux
as it traverses the liquid argon volume. A set of 2,631 candidate interactions
is divided in bins of the neutron kinetic energy calculated from time-of-flight
measurements. These interactions are reconstructed with custom-made algorithms
specifically designed for the data in a time projection chamber the size of the
Mini-CAPTAIN detector. The energy averaged cross section is . A comparison
of the measured cross section is made to the GEANT4 and FLUKA event generator
packages.Comment: 5 pages, 1 table, 3 figures, submitted to Physical Review Letter
Dark matter search in nucleon, pion, and electron channels from a proton beam dump with MiniBooNE
A search for sub-GeV dark matter produced from collisions of the Fermilab 8
GeV Booster protons with a steel beam dump was performed by the MiniBooNE-DM
Collaboration using data from protons on target in a
dedicated run. The MiniBooNE detector, consisting of 818 tons of mineral oil
and located 490 meters downstream of the beam dump, is sensitive to a variety
of dark matter initiated scattering reactions. Three dark matter interactions
are considered for this analysis: elastic scattering off nucleons, inelastic
neutral pion production, and elastic scattering off electrons. Multiple data
sets were used to constrain flux and systematic errors, and time-of-flight
information was employed to increase sensitivity to higher dark matter masses.
No excess from the background predictions was observed, and 90 confidence
level limits were set on the vector portal and leptophobic dark matter models.
New parameter space is excluded in the vector portal dark matter model with a
dark matter mass between 5 and 50. The reduced neutrino
flux allowed to test if the MiniBooNE neutrino excess scales with the
production of neutrinos. No excess of neutrino oscillation events were measured
ruling out models that scale solely by number of protons on target independent
of beam configuration at 4.6.Comment: 19 pages, 25 figures, Data release:
http://www-boone.fnal.gov/for_physicists/data_release/dark_matter_prd/ v2
Updated to published versio
Primary biliary cirrhosis
Primary biliary cirrhosis (PBC) is an immune-mediated chronic cholestatic liver disease with a slowly progressive course. Without treatment, most patients eventually develop fibrosis and cirrhosis of the liver and may need liver transplantation in the late stage of disease. PBC primarily affects women (female preponderance 9β10:1) with a prevalence of up to 1 in 1,000 women over 40Β years of age. Common symptoms of the disease are fatigue and pruritus, but most patients are asymptomatic at first presentation. The diagnosis is based on sustained elevation of serum markers of cholestasis, i.e., alkaline phosphatase and gamma-glutamyl transferase, and the presence of serum antimitochondrial antibodies directed against the E2 subunit of the pyruvate dehydrogenase complex. Histologically, PBC is characterized by florid bile duct lesions with damage to biliary epithelial cells, an often dense portal inflammatory infiltrate and progressive loss of small intrahepatic bile ducts. Although the insight into pathogenetic aspects of PBC has grown enormously during the recent decade and numerous genetic, environmental, and infectious factors have been disclosed which may contribute to the development of PBC, the precise pathogenesis remains enigmatic. Ursodeoxycholic acid (UDCA) is currently the only FDA-approved medical treatment for PBC. When administered at adequate doses of 13β15Β mg/kg/day, up to two out of three patients with PBC may have a normal life expectancy without additional therapeutic measures. The mode of action of UDCA is still under discussion, but stimulation of impaired hepatocellular and cholangiocellular secretion, detoxification of bile, and antiapoptotic effects may represent key mechanisms. One out of three patients does not adequately respond to UDCA therapy and may need additional medical therapy and/or liver transplantation. This review summarizes current knowledge on the clinical, diagnostic, pathogenetic, and therapeutic aspects of PBC
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