-
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 expected number of
atmospheric background is $0.082 \pm 0.004 \text{(stat)}^{+0.041}_{-0.057}
\text{(syst)}$. The probability to observe two or more candidate events under
the atmospheric background-only hypothesis is $2.9\times10^{-3}$ ($2.8\sigma$)
taking into account the uncertainty on the expected number of background
events. These two events could be a first indication of an astrophysical
neutrino flux, the moderate significance, however, does not permit a definitive
conclusion at this time.
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,
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
-
P. Scott,
C. Savage,
J. Edsjö,
the IceCube Collaboration: R. Abbasi,
Y. Abdou,
M. Ackermann,
J. Adams,
J. A. Aguilar,
M. Ahlers,
D. Altmann, [......],
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 a fast likelihood method for including event-level neutrino
telescope data in parameter explorations of theories for new physics, and
announce its public release as part of DarkSUSY 5.0.6. Our construction
includes both angular and spectral information about neutrino events, as well
as their total number. We also present a corresponding measure for simple model
exclusion, which can be used for single models without reference to the rest of
a parameter space. We perform a number of supersymmetric parameter scans with
IceCube data to illustrate the utility of the method: example global fits and a
signal recovery in the constrained minimal supersymmetric standard model
(CMSSM), and a model exclusion exercise in a 7-parameter phenomenological
version of the MSSM. The final IceCube detector configuration will probe almost
the entire focus-point region of the CMSSM, as well as a number of MSSM-7
models that will not otherwise be accessible to e.g. direct detection. Our
method accurately recovers the mock signal, and provides tight constraints on
model parameters and derived quantities. We show that the inclusion of spectral
information significantly improves the accuracy of the recovery, providing
motivation for its use in future IceCube analyses.
Journal of Cosmology and Astroparticle Physics 11/2012; 2012. · 5.72 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
-
The 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: A search for muon neutrinos from dark matter annihilations in the Galactic
Center region has been performed with the 40-string configuration of the
IceCube Neutrino Observatory using data collected in 367 days of live-time
starting in April 2008. The observed fluxes were consistent with the
atmospheric background expectations. Upper limits on the self-annihilation
cross-section are obtained for dark matter particle masses ranging from 100 GeV
to 10 TeV. In the case of decaying dark matter, lower limits on the lifetime
have been determined for masses between 200 GeV and 20 TeV.
10/2012;
-
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
