422 research outputs found
Moon Shadow by Cosmic Rays under the Influence of Geomagnetic Field and Search for Antiprotons at Multi-TeV Energies
We have observed the shadowing of galactic cosmic ray flux in the direction
of the moon, the so-called moon shadow, using the Tibet-III air shower array
operating at Yangbajing (4300 m a.s.l.) in Tibet since 1999. Almost all cosmic
rays are positively charged; for that reason, they are bent by the geomagnetic
field, thereby shifting the moon shadow westward. The cosmic rays will also
produce an additional shadow in the eastward direction of the moon if cosmic
rays contain negatively charged particles, such as antiprotons, with some
fraction. We selected 1.5 x10^{10} air shower events with energy beyond about 3
TeV from the dataset observed by the Tibet-III air shower array and detected
the moon shadow at level. The center of the moon was detected
in the direction away from the apparent center of the moon by 0.23 to
the west. Based on these data and a full Monte Carlo simulation, we searched
for the existence of the shadow produced by antiprotons at the multi-TeV energy
region. No evidence of the existence of antiprotons was found in this energy
region. We obtained the 90% confidence level upper limit of the flux ratio of
antiprotons to protons as 7% at multi-TeV energies.Comment: 13pages,4figures; Accepted for publication in Astroparticle Physic
Inclusive production of protons, anti-protons and neutrons in p+p collisions at 158 GeV/c beam momentum
New data on the production of protons, anti-protons and neutrons in p+p
interactions are presented. The data come from a sample of 4.8 million
inelastic events obtained with the NA49 detector at the CERN SPS at 158 GeV/c
beam momentum. The charged baryons are identified by energy loss measurement in
a large TPC tracking system. Neutrons are detected in a forward hadronic
calorimeter. Inclusive invariant cross sections are obtained in intervals from
0 to 1.9 GeV/c (0 to 1.5 GeV/c) in transverse momentum and from -0.05 to 0.95
(-0.05 to 0.4) in Feynman x for protons (anti-protons), respectively. pT
integrated neutron cross sections are given in the interval from 0.1 to 0.9 in
Feynman x. The data are compared to a wide sample of existing results in the
SPS and ISR energy ranges as well as to proton and neutron measurements from
HERA and RHIC.Comment: 69 pages, 72 figure
Combined point of care nucleic acid and antibody testing for SARS-CoV-2 following emergence of D614G Spike Variant
Rapid COVID-19 diagnosis in hospital is essential, though complicated by 30-50% of nose/throat swabs being negative by SARS-CoV-2 nucleic acid amplification testing (NAAT). Furthermore, the D614G spike mutant now dominates the pandemic and it is unclear how serological tests designed to detect anti-Spike antibodies perform against this variant. We assess the diagnostic accuracy of combined rapid antibody point of care (POC) and nucleic acid assays for suspected COVID-19 disease due to either wild type or the D614G spike mutant SARS-CoV-2. The overall detection rate for COVID-19 is 79.2% (95CI 57.8-92.9%) by rapid NAAT alone. Combined point of care antibody test and rapid NAAT is not impacted by D614G and results in very high sensitivity for COVID-19 diagnosis with very high specificity
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