175 research outputs found
Detecting a stochastic gravitational wave background with the Laser Interferometer Space Antenna
The random superposition of many weak sources will produce a stochastic
background of gravitational waves that may dominate the response of the LISA
(Laser Interferometer Space Antenna) gravitational wave observatory. Unless
something can be done to distinguish between a stochastic background and
detector noise, the two will combine to form an effective noise floor for the
detector. Two methods have been proposed to solve this problem. The first is to
cross-correlate the output of two independent interferometers. The second is an
ingenious scheme for monitoring the instrument noise by operating LISA as a
Sagnac interferometer. Here we derive the optimal orbital alignment for
cross-correlating a pair of LISA detectors, and provide the first analytic
derivation of the Sagnac sensitivity curve.Comment: 9 pages, 11 figures. Significant changes to the noise estimate
Calibration and Characterization of the IceCube Photomultiplier Tube
Over 5,000 PMTs are being deployed at the South Pole to compose the IceCube
neutrino observatory. Many are placed deep in the ice to detect Cherenkov light
emitted by the products of high-energy neutrino interactions, and others are
frozen into tanks on the surface to detect particles from atmospheric cosmic
ray showers. IceCube is using the 10-inch diameter R7081-02 made by Hamamatsu
Photonics. This paper describes the laboratory characterization and calibration
of these PMTs before deployment. PMTs were illuminated with pulses ranging from
single photons to saturation level. Parameterizations are given for the single
photoelectron charge spectrum and the saturation behavior. Time resolution,
late pulses and afterpulses are characterized. Because the PMTs are relatively
large, the cathode sensitivity uniformity was measured. The absolute photon
detection efficiency was calibrated using Rayleigh-scattered photons from a
nitrogen laser. Measured characteristics are discussed in the context of their
relevance to IceCube event reconstruction and simulation efforts.Comment: 40 pages, 12 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
The IceCube Neutrino Observatory Part VI: Ice Properties, Reconstruction and Future Developments
Papers on ice properties, reconstruction and future developments submitted to
the 33nd International Cosmic Ray Conference (Rio de Janeiro 2013) by the
IceCube Collaboration.Comment: 28 pages, 38 figures; Papers submitted to the 33nd International
Cosmic Ray Conference, Rio de Janeiro 2013; version 2 corrects errors in the
author lis
Search for Relativistic Magnetic Monopoles with IceCube
We present the first results in the search for relativistic magnetic
monopoles with the IceCube detector, a subsurface neutrino telescope located in
the South Polar ice cap containing a volume of 1 km. This analysis
searches data taken on the partially completed detector during 2007 when
roughly 0.2 km of ice was instrumented. The lack of candidate events
leads to an upper limit on the flux of relativistic magnetic monopoles of
\Phi_{\mathrm{90%C.L.}}\sim 3\e{-18}\fluxunits for . This is a
factor of 4 improvement over the previous best experimental flux limits up to a
Lorentz boost below . This result is then interpreted for a
wide range of mass and kinetic energy values.Comment: 11 pages, 11 figures. v2 is minor text edits, no changes to resul
Lateral Distribution of Muons in IceCube Cosmic Ray Events
In cosmic ray air showers, the muon lateral separation from the center of the
shower is a measure of the transverse momentum that the muon parent acquired in
the cosmic ray interaction. IceCube has observed cosmic ray interactions that
produce muons laterally separated by up to 400 m from the shower core, a factor
of 6 larger distance than previous measurements. These muons originate in high
pT (> 2 GeV/c) interactions from the incident cosmic ray, or high-energy
secondary interactions. The separation distribution shows a transition to a
power law at large values, indicating the presence of a hard pT component that
can be described by perturbative quantum chromodynamics. However, the rates and
the zenith angle distributions of these events are not well reproduced with the
cosmic ray models tested here, even those that include charm interactions. This
discrepancy may be explained by a larger fraction of kaons and charmed
particles than is currently incorporated in the simulations
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
Solar Energetic Particle Spectrum on 13 December 2006 Determined by IceTop
On 13 December 2006 the IceTop air shower array at the South Pole detected a
major solar particle event. By numerically simulating the response of the
IceTop tanks, which are thick Cherenkov detectors with multiple thresholds
deployed at high altitude with no geomagnetic cut-off, we determined the
particle energy spectrum in the energy range 0.6 to 7.6 GeV. This is the first
such spectral measurement using a single instrument with a well defined viewing
direction. We compare the IceTop spectrum and its time evolution with
previously published results and outline plans for improved resolution of
future solar particle spectra.Comment: To appear in Astrophysical Journal Letters, 6 pages, 4 figure
The DUNE Far Detector Interim Design Report, Volume 3: Dual-Phase Module
The DUNE IDR describes the proposed physics program and technical designs of the DUNE far detector modules in preparation for the full TDR to be published in 2019. It is intended as an intermediate milestone on the path to a full TDR, justifying the technical choices that flow down from the high-level physics goals through requirements at all levels of the Project. These design choices will enable the DUNE experiment to make the ground-breaking discoveries that will help to answer fundamental physics questions. Volume 3 describes the dual-phase module's subsystems, the technical coordination required for its design, construction, installation, and integration, and its organizational structure
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