-
IceCube Collaboration,
M. G. Aartsen,
R. Abbasi,
Y. Abdou,
M. Ackermann,
J. Adams,
J. A. Aguilar,
M. Ahlers,
D. Altmann,
K. Andeen, [......],
D. L. Xu,
X. W. Xu,
J. P. Yanez,
G. Yodh,
S. Yoshida,
P. Zarzhitsky,
J. Ziemann,
S. Zierke,
A. Zilles,
M. Zoll
[show abstract]
[hide abstract]
ABSTRACT: We report on the observation of anisotropy in the arrival direction
distribution of cosmic rays at PeV energies. The analysis is based on data
taken between 2009 and 2012 with the IceTop air shower array at the South Pole.
IceTop, an integral part of the IceCube detector, is sensitive to cosmic rays
between 100 TeV and 1 EeV. With the current size of the IceTop data set,
searches for anisotropy at the 10^-3 level can, for the first time, be extended
to PeV energies. We divide the data set into two parts with median energies of
400 TeV and 2 PeV, respectively. In the low energy band, we observe a strong
deficit with an angular size of about 30 degrees and an amplitude of (-1.58 +/-
0.46 (stat) +/- 0.52 (sys)) x 10^(-3) at a location consistent with previous
observations of cosmic rays with the IceCube neutrino detector. The study of
the high energy band shows that the anisotropy persists to PeV energies and
increases in amplitude to (-3.11 +/- 0.38 (stat) +/- 0.96 (sys)) x 10^(-3).
The Astrophysical Journal 10/2013; 765(1):55. · 6.02 Impact Factor
-
IceCube Collaboration,
R. Abbasi,
Y. Abdou,
M. Ackermann,
J. Adams,
J. A. Aguilar,
M. Ahlers,
D. Altmann,
K. Andeen,
J. Auffenberg, [......],
C. Xu,
D. L. Xu,
X. W. Xu,
J. P. Yanez,
G. Yodh,
S. Yoshida,
P. Zarzhitsky,
J. Ziemann,
A. Zilles,
M. Zoll
[show abstract]
[hide abstract]
ABSTRACT: 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$^{3}$. This analysis
searches data taken on the partially completed detector during 2007 when
roughly 0.2 km$^{3}$ 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 $\beta\geq0.8$. This is a
factor of 4 improvement over the previous best experimental flux limits up to a
Lorentz boost $\gamma$ below $10^{7}$. This result is then interpreted for a
wide range of mass and kinetic energy values.
Physical Review D 08/2013; 87(2):022001. · 4.56 Impact Factor
-
IceCube Collaboration,
M. G. Aartsen,
R. Abbasi,
Y. Abdou,
M. Ackermann,
J. Adams,
J. A. Aguilar,
M. Ahlers,
D. Altmann,
J. Auffenberg, [......],
D. L. Xu,
X. W. Xu,
J. P. Yanez,
G. Yodh,
S. Yoshida,
P. Zarzhitsky,
J. Ziemann,
S. Zierke,
A. Zilles,
M. Zoll
[show abstract]
[hide abstract]
ABSTRACT: The IceCube Neutrino Observatory, approximately 1 km^3 in size, is now
complete with 86 strings deployed in the Antarctic ice. IceCube detects the
Cherenkov radiation emitted by charged particles passing through or created in
the ice. To realize the full potential of the detector, the properties of light
propagation in the ice in and around the detector must be well understood. This
report presents a new method of fitting the model of light propagation in the
ice to a data set of in-situ light source events collected with IceCube. The
resulting set of derived parameters, namely the measured values of scattering
and absorption coefficients vs. depth, is presented and a comparison of IceCube
data with simulations based on the new model is shown.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 05/2013; A711:73-89. · 1.21 Impact Factor
-
IceCube Collaboration,
M. G. Aartsen,
R. Abbasi,
Y. Abdou,
M. Ackermann,
J. Adams,
J. A. Aguilar,
M. Ahlers,
D. Altmann,
J. Auffenberg, [......],
D. L. Xu,
X. W. Xu,
J. P. Yanez,
G. Yodh,
S. Yoshida,
P. Zarzhitsky,
J. Ziemann,
S. Zierke,
A. Zilles,
M. Zoll
[show abstract]
[hide abstract]
ABSTRACT: We report on the observation of two neutrino-induced events which have an
estimated deposited energy in the IceCube detector of $1.04 \pm 0.16$ and $1.14
\pm 0.17$\,PeV, respectively, the highest neutrino energies observed so far.
These events are consistent with fully contained particle showers induced by
neutral-current $\nu_{e,\mu,\tau}$ ($\bar\nu_{e,\mu,\tau}$) or charged-current
$\nu_{e}$ ($\bar\nu_{e}$) interactions within the IceCube detector. The events
were discovered in a search for ultra-high energy neutrinos using data
corresponding to 615.9 days effective livetime. The two neutrino events are
observed over an expected atmospheric background of $0.082 \pm 0.004
\text{(stat)}^{+0.041}_{-0.057} \text{(syst)}$. The resulting p-value for the
background-only hypothesis is $2.9\times10^{-3}$ ($2.8\sigma$) taking into
account the uncertainty on the expected number of background events. Though the
two events could be a first indication of an astrophysical neutrino flux, the
moderate significance and the uncertainties on the expected atmospheric
background from neutrinos produced in the decay of charmed mesons do not allow
for a firm conclusion at this point.
04/2013;
-
IceCube Collaboration,
M. G. Aartsen,
R. Abbasi,
Y. Abdou,
M. Ackermann,
J. Adams,
J. A. Aguilar,
M. Ahlers,
D. Altmann,
K. Andeen, [......],
D. L. Xu,
X. W. Xu,
J. P. Yanez,
G. Yodh,
S. Yoshida,
P. Zarzhitsky,
J. Ziemann,
S. Zierke,
A. Zilles,
M. Zoll
[show abstract]
[hide abstract]
ABSTRACT: We report the first measurement of the atmospheric electron neutrino flux in
the energy range between approximately 80 GeV and 6 TeV, using data recorded
during the first year of operation of IceCube's DeepCore low energy extension.
Techniques to identify neutrinos interacting within the DeepCore volume and
veto muons originating outside the detector are demonstrated. A sample of 1029
events is observed in 281 days of data, of which 496 $\pm$ 66(stat.) $\pm$
88(syst.) are estimated to be cascade events, including both electron neutrino
and neutral current events. The rest of the sample includes residual
backgrounds due to atmospheric muons and charged current interactions of
atmospheric muon neutrinos. The flux of the atmospheric electron neutrinos is
consistent with models of atmospheric neutrinos in this energy range. This
constitutes the first observation of electron neutrinos and neutral current
interactions in a very large volume neutrino telescope optimized for the TeV
energy range.
Physical Review Letters 04/2013; 110:151105. · 7.37 Impact Factor
-
IceCube Collaboration,
R. Abbasi,
Y. Abdou,
T. Abu-Zayyad,
M. Ackermann,
J. Adams,
J. A. Aguilar,
M. Ahlers,
D. Altmann,
K. Andeen, [......],
T. R. Wood,
K. Woschnagg,
C. Xu,
D. L. Xu,
X. W. Xu,
J. P. Yanez,
G. Yodh,
S. Yoshida,
P. Zarzhitsky,
M. Zoll
[show abstract]
[hide abstract]
ABSTRACT: 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.
Astroparticle Physics 04/2013; 44:40-58. · 3.22 Impact Factor
-
IceCube collaboration,
R. Abbasi,
Y. Abdou,
M. Ackermann,
J. Adams,
J. A. Aguilar,
M. Ahlers,
D. Altmann,
K. Andeen,
J. Auffenberg, [......],
C. Xu,
D. L. Xu,
X. W. Xu,
J. P. Yanez,
G. Yodh,
S. Yoshida,
P. Zarzhitsky,
J. Ziemann,
A. Zilles,
M. Zoll
[show abstract]
[hide abstract]
ABSTRACT: 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.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 03/2013; A703(1):190-198. · 1.21 Impact Factor
-
IceCube collaboration,
M. G. Aartsen,
R. Abbasi,
Y. Abdou,
M. Ackermann,
J. Adams,
J. A. Aguilar,
M. Ahlers,
D. Altmann,
K. Andeen, [......],
D. L. Xu,
X. W. Xu,
J. P. Yanez,
G. Yodh,
S. Yoshida,
P. Zarzhitsky,
J. Ziemann,
S. Zierke,
A. Zilles,
M. Zoll
[show abstract]
[hide abstract]
ABSTRACT: We have performed a search for muon neutrinos from dark matter annihilation
in the center of the Sun with the 79-string configuration of the IceCube
neutrino telescope. For the first time, the DeepCore sub-array is included in
the analysis, lowering the energy threshold and extending the search to the
austral summer. The 317 days of data collected between June 2010 and May 2011
are consistent with the expected background from atmospheric muons and
neutrinos. Upper limits are therefore set on the dark matter annihilation rate,
with conversions to limits on spin-dependent and spin-independent WIMP-proton
cross-sections for WIMP masses in the range 20 - 5000 GeV. These are the most
stringent spin-dependent WIMP-proton cross-sections limits to date above 35
GeV.
Physical Review Letters 02/2013; · 7.37 Impact Factor
-
IceCube Collaboration,
R. Abbasi,
Y. Abdou,
M. Ackermann,
J. Adams,
J. A. Aguilar,
M. Ahlers,
D. Altmann,
K. Andeen,
J. Auffenberg, [......],
C. Xu,
D. L. Xu,
X. W. Xu,
J. P. Yanez,
G. Yodh,
S. Yoshida,
P. Zarzhitsky,
J. Ziemann,
A. Zilles,
M. Zoll
[show abstract]
[hide abstract]
ABSTRACT: The mass composition of high energy cosmic rays depends on their production,
acceleration, and propagation. The study of cosmic ray composition can
therefore reveal hints of the origin of these particles. At the South Pole, the
IceCube Neutrino Observatory is capable of measuring two components of cosmic
ray air showers in coincidence: the electromagnetic component at high altitude
(2835 m) using the IceTop surface array, and the muonic component above ~1 TeV
using the IceCube array. This unique detector arrangement provides an
opportunity for precision measurements of the cosmic ray energy spectrum and
composition in the region of the knee and beyond. We present the results of a
neural network analysis technique to study the cosmic ray composition and the
energy spectrum from 1 PeV to 30 PeV using data recorded using the
40-string/40-station configuration of the IceCube Neutrino Observatory.
Astroparticle Physics 02/2013; 42:15-32. · 3.22 Impact Factor
-
IceCube Collaboration,
R. Abbasi,
Y. Abdou,
M. Ackermann,
J. Adams,
J. A. Aguilar,
M. Ahlers,
D. Altmann,
K. Andeen,
J. Auffenberg, [......],
C. Xu,
D. L. Xu,
X. W. Xu,
J. P. Yanez,
G. Yodh,
S. Yoshida,
P. Zarzhitsky,
J. Ziemann,
A. Zilles,
M. Zoll
[show abstract]
[hide abstract]
ABSTRACT: IceTop, the surface component of the IceCube Neutrino Observatory at the
South Pole, is an air shower array with an area of 1 km2. The detector allows a
detailed exploration of the mass composition of primary cosmic rays in the
energy range from about 100 TeV to 1 EeV by exploiting the correlation between
the shower energy measured in IceTop and the energy deposited by muons in the
deep ice. In this paper we report on the technical design, construction and
installation, the trigger and data acquisition systems as well as the software
framework for calibration, reconstruction and simulation. Finally the first
experience from commissioning and operating the detector and the performance as
an air shower detector will be discussed.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 02/2013; 700:188-220. · 1.21 Impact Factor
-
IceCube Collaboration,
R. Abbasi,
Y. Abdou,
M. Ackermann,
J. Adams,
J. A. Aguilar,
M. Ahlers,
D. Altmann,
K. Andeen,
J. Auffenberg, [......],
C. Xu,
D. L. Xu,
X. W. Xu,
J. P. Yanez,
G. Yodh,
S. Yoshida,
P. Zarzhitsky,
J. Ziemann,
A. Zilles,
M. Zoll
[show abstract]
[hide abstract]
ABSTRACT: 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.
Physical Review D 01/2013; 87:012005. · 4.56 Impact Factor
-
IceCube collaboration,
M. G. Aartsen,
R. Abbasi,
Y. Abdou,
M. Ackermann,
J. Adams,
J. A. Aguilar,
M. Ahlers,
D. Altmann,
K. Andeen, [......],
D. L. Xu,
X. W. Xu,
J. P. Yanez,
G. Yodh,
S. Yoshida,
P. Zarzhitsky,
J. Ziemann,
S. Zierke,
A. Zilles,
M. Zoll
[show abstract]
[hide abstract]
ABSTRACT: Gamma-ray induced air showers are notable for their lack of muons, compared
to hadronic showers. Hence, air shower arrays with large underground muon
detectors can select a sample greatly enriched in photon showers by rejecting
showers containing muons. IceCube is sensitive to muons with energies above
~500 GeV at the surface, which provides an efficient veto system for hadronic
air showers with energies above 1 PeV. One year of data from the 40-string
IceCube configuration was used to perform a search for point sources and a
Galactic diffuse signal. No sources were found, resulting in a 90% C.L. upper
limit on the ratio of gamma rays to cosmic rays of 1.2 x 10^(-3)for the flux
coming from the Galactic Plane region (-80 deg < l < -30 deg; -10 deg < b < 5
deg) in the energy range 1.2 - 6.0 PeV. In the same energy range, point source
fluxes with E^(-2) spectra have been excluded at a level of (E/TeV)^2 d\Phi/dE
~ 10^(-12)-10^(-11) cm^2/s/TeV depending on source declination. The complete
IceCube detector will have a better sensitivity, due to the larger detector
size, improved reconstruction and vetoing techniques. Preliminary data from the
nearly-final IceCube detector configuration has been used to estimate the 5
year sensitivity of the full detector. It is found to be more than an order of
magnitude better, allowing the search for PeV extensions of known TeV gamma-ray
emitters.
Physical Review D 10/2012; · 4.56 Impact Factor
-
IceCube collaboration,
R. Abbasi,
Y. Abdou,
M. Ackermann,
J. Adams,
J. A. Aguilar,
M. Ahlers,
D. Altmann,
K. Andeen,
J. Auffenberg, [......],
C. Xu,
D. L. Xu,
X. W. Xu,
J. P. Yanez,
G. Yodh,
S. Yoshida,
P. Zarzhitsky,
J. Ziemann,
A. Zilles,
M. Zoll
[show abstract]
[hide abstract]
ABSTRACT: We report on searches for neutrino sources at energies above 200 GeV in the
Northern sky of the galactic plane, using the data collected by the South Pole
neutrino telescopes IceCube and AMANDA. The galactic region considered here
includes the Local Arm towards the Cygnus region and our closest approach to
the Perseus Arm. The data have been collected between 2007 and 2009 when AMANDA
was an integrated part of IceCube, which was still under construction and
operated with 22-strings (2007-8) and 40-strings (2008-9) of optical modules
deployed in the ice. By combining the larger IceCube detector with the lower
energy threshold of the more compact AMANDA detector, we obtain an improved
sensitivity at energies below $\sim$10 TeV with respect to previous searches.
The analyses presented here are: a scan for point sources within the galactic
plane; a search optimized for multiple and extended sources in the Cygnus
region, which might be below the sensitivity of the point source scan; and
studies of seven pre-selected neutrino source candidates. For one of them,
Cygnus X-3, a time-dependent search for neutrinos in coincidence with observed
radio and X-ray flares has been performed. No evidence of a signal is found,
and upper limits are reported for each of the searches. We investigate neutrino
spectra proportional to E$^{-2}$ and E$^{-3}$ to cover the entire range of
possible spectra. The soft E$^{-3}$ spectrum results in an energy distribution
similar to a source with cut-off below $\sim$50 TeV. For the considered region
of the galactic plane, the 90% confidence level muon neutrino flux upper limits
are in the range E$^3$dN/dE$\sim 5.4 - 19.5 \times 10^{-11} \rm{TeV^{2} cm^{-2}
s^{-1}}$ for point-like neutrino sources in the energy region [180.0 GeV - 20.5
TeV]. These represent the most stringent upper limits for soft-spectra neutrino
sources within the Galaxy reported to date.
The Astrophysical Journal 10/2012; 783(1):33. · 6.02 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The IceCube neutrino observatory in operation at the South Pole, Antarctica, comprises three distinct components: a large buried array for ultrahigh energy neutrino detection, a surface air shower array, and a new buried component called DeepCore. DeepCore was designed to lower the IceCube neutrino energy threshold by over an order of magnitude, to energies as low as about 10 GeV. DeepCore is situated primarily 2100 m below the surface of the icecap at the South Pole, at the bottom center of the existing IceCube array, and began taking physics data in May 2010. Its location takes advantage of the exceptionally clear ice at those depths and allows it to use the surrounding IceCube detector as a highly efficient active veto against the principal background of downward-going muons produced in cosmic-ray air showers. DeepCore has a module density roughly five times higher than that of the standard IceCube array, and uses photomultiplier tubes with a new photocathode featuring a quantum efficiency about 35% higher than standard IceCube PMTs. Taken together, these features of DeepCore will increase IceCube’s sensitivity to neutrinos from WIMP dark matter annihilations, atmospheric neutrino oscillations, galactic supernova neutrinos, and point sources of neutrinos in the northern and southern skies. In this paper we describe the design and initial performance of DeepCore.
Astroparticle Physics 05/2012; 35(10):615-624. · 3.22 Impact Factor
-
IceCube Collaboration,
R. Abbasi,
Y. Abdou,
T. Abu-Zayyad,
M. Ackermann,
J. Adams,
J. A. Aguilar,
M. Ahlers,
D. Altmann,
K. Andeen, [......],
T. R. Wood,
K. Woschnagg,
C. Xu,
D. L. Xu,
X. W. Xu,
J. P. Yanez,
G. Yodh,
S. Yoshida,
P. Zarzhitsky,
M. Zoll
[show abstract]
[hide abstract]
ABSTRACT: Gamma-Ray Bursts (GRBs) have been proposed as a leading candidate for
acceleration of ultra high-energy cosmic rays, which would be accompanied by
emission of TeV neutrinos produced in proton-photon interactions during
acceleration in the GRB fireball. Two analyses using data from two years of the
IceCube detector produced no evidence for this neutrino emission, placing
strong constraints on models of neutrino and cosmic-ray production in these
sources.
Nature 04/2012; 484:351. · 36.28 Impact Factor
-
IceCube Collaboration,
R. Abbasi,
Y. Abdou,
T. Abu-Zayyad,
M. Ackermann,
J. Adams,
J. A. Aguilar,
M. Ahlers,
M. M. Allen,
D. Altmann, [......],
T. R. Wood,
K. Woschnagg,
C. Xu,
D. L. Xu,
X. W. Xu,
J. P. Yanez,
G. Yodh,
S. Yoshida,
P. Zarzhitsky,
M. Zoll
[show abstract]
[hide abstract]
ABSTRACT: In this paper we present the results of searches for periodic neutrino
emission from a catalog of binary systems. Such modulation, observed in the
photon flux, would be caused by the geometry of these systems. In the analysis,
the period is fixed by these photon observations, while the phase and duration
of the neutrino emission are treated as free parameters to be fit with the
data. If the emission occurs during ~20% or less of the total period, this
analysis achieves better sensitivity than a time-integrated analysis. We use
the IceCube data taken from May 31, 2007 to April 5, 2008 with its 22-string
configuration, and from April 5, 2008 to May 20, 2009 with its 40-string
configuration. No evidence for neutrino emission is found, with the strongest
excess occurring for Cygnus X-3 at 2.1 sigma significance after accounting for
trials. Neutrino flux upper limits for both periodic and time-integrated
emission are provided.
The Astrophysical Journal 04/2012; 748(2):118. · 6.02 Impact Factor
-
IceCube Collaboration,
R. Abbasi,
Y. Abdou,
T. Abu-Zayyad,
M. Ackermann,
J. Adams,
J. A. Aguilar,
M. Ahlers,
D. Altmann,
K. Andeen, [......],
T. R. Wood,
K. Woschnagg,
C. Xu,
D. L. Xu,
X. W. Xu,
J. P. Yanez,
G. Yodh,
S. Yoshida,
P. Zarzhitsky,
M. Zoll
[show abstract]
[hide abstract]
ABSTRACT: A search for an excess of muon-neutrinos from dark matter annihilations in
the Sun has been performed with the AMANDA-II neutrino telescope using data
collected in 812 days of livetime between 2001 and 2006 and 149 days of
livetime collected with the AMANDA-II and the 40-string configuration of
IceCube during 2008 and early 2009. No excess over the expected atmospheric
neutrino background has been observed. We combine these results with the
previously published IceCube limits obtained with data taken during 2007 to
obtain a total livetime of 1065 days. We provide an upper limit at 90%
confidence level on the annihilation rate of captured neutralinos in the Sun,
as well as the corresponding muon flux limit at the Earth, both as functions of
the neutralino mass in the range 50 GeV-5000 GeV. We also derive a limit on the
neutralino-proton spin-dependent and spin-independent cross section. The limits
presented here improve the previous results obtained by the collaboration
between a factor of two and five, as well as extending the neutralino masses
probed down to 50 GeV. The spin-dependent cross section limits are the most
stringent so far for neutralino masses above 200 GeV, and well below direct
search results in the mass range from 50 GeV to 5 TeV.
Physical Review D 02/2012; 85:042002. · 4.56 Impact Factor
-
IceCube Collaboration,
R. Abbasi,
Y. Abdou,
T. Abu-Zayyad,
M. Ackermann,
J. Adams,
J. A. Aguilar,
M. Ahlers,
D. Altmann,
K. Andeen, [......],
T. R. Wood,
K. Woschnagg,
C. Xu,
D. L. Xu,
X. W. Xu,
J. P. Yanez,
G. Yodh,
S. Yoshida,
P. Zarzhitsky,
M. Zoll
[show abstract]
[hide abstract]
ABSTRACT: The first dedicated search for ultra-high energy (UHE) tau neutrinos of
astrophysical origin was performed using the IceCube detector in its 22-string
configuration with an instrumented volume of roughly 0.25 km^3. The search also
had sensitivity to UHE electron and muon neutrinos. After application of all
selection criteria to approximately 200 live-days of data, we expect a
background of 0.60 +/- 0.19 (stat.) $^{+0.56}_{-0.58}$ (syst.) events and
observe three events, which after inspection emerge as being compatible with
background but are kept in the final sample. Therefore, we set an upper limit
on neutrinos of all-flavors from UHE astrophysical sources at 90% CL of $E^{2}
\Phi(\nu_{x}) < 16.3 * 10^-8 GeV cm^-2 sr^-1 s^-1 over an estimated primary
neutrino energy range of 340 TeV to 200 PeV.
Physical Review D 02/2012; 86(02):022005. · 4.56 Impact Factor
-
IceCube Collaboration,
R. Abbasi,
Y. Abdou,
T. Abu-Zayyad,
M. Ackermann,
J. Adams,
J. A. Aguilar,
M. Ahlers,
M. M. Allen,
D. Altmann, [......],
T. R. Wood,
K. Woschnagg,
C. Xu,
D. L. Xu,
X. W. Xu,
J. P. Yanez,
G. Yodh,
S. Yoshida,
P. Zarzhitsky,
M. Zoll
[show abstract]
[hide abstract]
ABSTRACT: In this paper we report the first observation in the Southern hemisphere of
an energy dependence in the Galactic cosmic ray anisotropy up to a few hundred
TeV. This measurement was performed using cosmic ray induced muons recorded by
the partially deployed IceCube observatory between May 2009 and May 2010. The
data include a total of 33$\times 10^{9}$ muon events with a median angular
resolution of $\sim3^{\circ}$ degrees. A sky map of the relative intensity in
arrival direction over the Southern celestial sky is presented for cosmic ray
median energies of 20 and 400 TeV. The same large-scale anisotropy observed at
median energies around 20 TeV is not present at 400 TeV. Instead, the high
energy skymap shows a different anisotropy structure including a deficit with a
post-trial significance of -6.3$\sigma$. This anisotropy reveals a new feature
of the Galactic cosmic ray distribution, which must be incorporated into
theories of the origin and propagation of cosmic rays.
The Astrophysical Journal 01/2012; 746(1):33. · 6.02 Impact Factor
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IceCube Collaboration,
R. Abbasi,
Y. Abdou,
T. Abu-Zayyad,
J Adams,
J. A. Aguilar,
M. Ahlers,
D. Altmann,
K. Andeen,
J. Auffenberg, [......],
H. Wissing,
M Wolf,
T. R. Wood,
K Woschnagg,
C Xu,
X. W. Xu,
G. Yodh,
S Yoshida,
P. Zarzhitsky,
M. Zoll
[show abstract]
[hide abstract]
ABSTRACT: We present the results for a search of high-energy muon neutrinos with the
IceCube detector in coincidence with the Crab nebula flare reported on
September 2010 by various experiments. Due to the unusual flaring state of the
otherwise steady source we performed a prompt analysis of the 79-string
configuration data to search for neutrinos that might be emitted along with the
observed gamma-rays. We performed two different and complementary data
selections of neutrino events in the time window of 10 days around the flare.
One event selection is optimized for discovery of E^-2 neutrino spectrum
typical of 1st order Fermi acceleration. A similar event selection has also
been applied to the 40-string data to derive the time-integrated limits to the
neutrino emission from the Crab. The other event selection was optimized for
discovery of neutrino spectra with softer spectral index and TeV energy
cut-offs as observed for various galactic sources in gamma-rays. The 90% CL
best upper limits on the Crab flux during the 10 day flare are 4.73 x 10^-11
cm-2 s-1 TeV-1 for an E^-2 neutrino spectrum and 2.50 x 10^-10 cm-2 s-1 TeV-1
for a softer neutrino spectra of E-2.7, as indicated by Fermi measurements
during the flare. IceCube has also set a time-integrated limit on the neutrino
emission of the Crab using 375.5 days of livetime of the 40-string
configuration data. This limit is compared to existing models of neutrino
production from the Crab and its impact on astrophysical parameters is
discussed. The most optimistic predictions of some models are already rejected
by the IceCube neutrino telescope with more than 90% CL.
The Astrophysical Journal 01/2012; 745(1). · 6.02 Impact Factor
