20 research outputs found
An improved method for measuring muon energy using the truncated mean of dE/dx
The measurement of muon energy is critical for many analyses in large
Cherenkov detectors, particularly those that involve separating
extraterrestrial neutrinos from the atmospheric neutrino background. Muon
energy has traditionally been determined by measuring the specific energy loss
(dE/dx) along the muon's path and relating the dE/dx to the muon energy.
Because high-energy muons (E_mu > 1 TeV) lose energy randomly, the spread in
dE/dx values is quite large, leading to a typical energy resolution of 0.29 in
log10(E_mu) for a muon observed over a 1 km path length in the IceCube
detector. In this paper, we present an improved method that uses a truncated
mean and other techniques to determine the muon energy. The muon track is
divided into separate segments with individual dE/dx values. The elimination of
segments with the highest dE/dx results in an overall dE/dx that is more
closely correlated to the muon energy. This method results in an energy
resolution of 0.22 in log10(E_mu), which gives a 26% improvement. This
technique is applicable to any large water or ice detector and potentially to
large scintillator or liquid argon detectors.Comment: 12 pages, 16 figure
All-particle cosmic ray energy spectrum measured with 26 IceTop stations
We report on a measurement of the cosmic ray energy spectrum with the IceTop
air shower array, the surface component of the IceCube Neutrino Observatory at
the South Pole. The data used in this analysis were taken between June and
October, 2007, with 26 surface stations operational at that time, corresponding
to about one third of the final array. The fiducial area used in this analysis
was 0.122 km^2. The analysis investigated the energy spectrum from 1 to 100 PeV
measured for three different zenith angle ranges between 0{\deg} and 46{\deg}.
Because of the isotropy of cosmic rays in this energy range the spectra from
all zenith angle intervals have to agree. The cosmic-ray energy spectrum was
determined under different assumptions on the primary mass composition. Good
agreement of spectra in the three zenith angle ranges was found for the
assumption of pure proton and a simple two-component model. For zenith angles
{\theta} < 30{\deg}, where the mass dependence is smallest, the knee in the
cosmic ray energy spectrum was observed between 3.5 and 4.32 PeV, depending on
composition assumption. Spectral indices above the knee range from -3.08 to
-3.11 depending on primary mass composition assumption. Moreover, an indication
of a flattening of the spectrum above 22 PeV were observed.Comment: 38 pages, 17 figure
Joint sequencing of human and pathogen genomes reveals the genetics of pneumococcal meningitis
Streptococcus pneumoniae is a common nasopharyngeal colonizer, but can also cause lifethreatening invasive diseases such as empyema, bacteremia and meningitis. Genetic variation
of host and pathogen is known to play a role in invasive pneumococcal disease, though to
what extent is unknown. In a genome-wide association study of human and pathogen we
show that human variation explains almost half of variation in susceptibility to pneumococcal
meningitis and one-third of variation in severity, identifying variants in CCDC33 associated
with susceptibility. Pneumococcal genetic variation explains a large amount of invasive
potential (70%), but has no effect on severity. Serotype alone is insufficient to explain
invasiveness, suggesting other pneumococcal factors are involved in progression to invasive
disease. We identify pneumococcal genes involved
Magnetospheric Science Objectives of the Juno Mission
In July 2016, NASA’s Juno mission becomes the first spacecraft to enter polar orbit of Jupiter and enture deep into unexplored polar territories of the magnetosphere. Focusing on these polar regions, we review current understanding of the structure and dynamics of the magnetosphere and summarize the outstanding issues. The Juno mission profile involves (a) a several-week approach from the dawn side of Jupiter’s magnetosphere, with an orbit-insertion maneuver on July 6, 2016; (b) a 107-day capture orbit, also on the dawn flank; and (c) a series of thirty 11-day science orbits with the spacecraft flying over Jupiter’s poles and ducking under the radiation belts. We show how Juno’s view of the magnetosphere evolves over the year of science orbits. The Juno spacecraft carries a range of instruments that take particles and fields measurements, remote sensing observations of auroral emissions at UV, visible, IR and radio wavelengths, and detect microwave emission from Jupiter’s radiation belts. We summarize how these Juno measurements address issues of auroral processes, microphysical plasma physics, ionosphere-magnetosphere and satellite-magnetosphere coupling, sources and sinks of plasma, the radiation belts, and the dynamics of the outer magnetosphere. To reach Jupiter, the Juno spacecraft passed close to the Earth on October 9, 2013, gaining the necessary energy to get to Jupiter. The Earth flyby provided an opportunity to test Juno’s instrumentation as well as take scientific data in the terrestrial magnetosphere, in conjunction with ground-based and Earth-orbiting assets
Measurement of Acoustic Attenuation in South Pole Ice
Using the South Pole Acoustic Test Setup (SPATS) and a retrievable
transmitter deployed in holes drilled for the IceCube experiment, we have
measured the attenuation of acoustic signals by South Pole ice at depths
between 190 m and 500 m. Three data sets, using different acoustic sources,
have been analyzed and give consistent results. The method with the smallest
systematic uncertainties yields an amplitude attenuation coefficient alpha =
3.20 \pm 0.57 km^(-1) between 10 and 30 kHz, considerably larger than previous
theoretical estimates. Expressed as an attenuation length, the analyses give a
consistent result for lambda = 1/alpha of ~1/300 m with 20% uncertainty. No
significant depth or frequency dependence has been found.Comment: 17 pages, 12 figures, published in Astroparticle Physics, 201
Measurement of South Pole Ice Transparency with the IceCube LED Calibration System
0IceCube Collaborationinfo:eu-repo/semantics/publishe