633 research outputs found
IceCube Sensitivity for Neutrino Flux from Fermi Blazars in Quiescent States
We investigate the IceCube detection potential of very high energy neutrinos
from blazars, for different classes of "hadronic" models, taking into account
the limits imposed on the neutrino flux by the recent Fermi telescope
observations. Assuming the observed gamma-ray emission is produced by the decay
of neutral pions from proton-proton interactions, the measurement of the
time-averaged spectral characteristics of blazars in the GeV energy band
imposes upper limits on the time-averaged neutrino flux. Comparing these upper
limits to the 5 sigma discovery threshold of IceCube for different neutrino
spectra and different source locations in the sky, we find that several BL Lacs
with hard spectra in the GeV band are within the detection potential of
IceCube. If the gamma-ray emission is dominated by the neutral pion decay flux,
none of the flat-spectrum radio quasars are detectable with IceCube. If the
primary high energy proton spectrum is very hard and/or neutrinos are produced
in proton-photon, rather than proton-proton reactions, the upper limit on the
neutrino flux imposed by the measured gamma-ray spectra is relaxed and
gamma-ray observations impose only lower bounds on the neutrino flux. We
investigate whether these lower bounds guarantee the detection of blazars with
very hard neutrino spectra, expected in the latter type model. We show that all
the "hadronic" models of activity of blazars are falsifiable with IceCube.
Furthermore, we show that models with gamma-ray emission produced by the decay
of neutral pions from proton-proton interactions can be readily distinguished
from the models based on proton-gamma interactions and/or models predicting
very hard high energy proton spectra via a study of the distribution of
spectral indices of gamma-ray spectra of sources detected with IceCube.Comment: 10 pages, 5 figure
Improving the neutrino mass hierarchy identification with inelasticity measurement in PINGU and ORCA
Multi-megaton scale under ice and underwater detectors of atmospheric
neutrinos with few GeV's energy threshold (PINGU, ORCA) open up new
possibilities in the determination of neutrino properties, and in particular
the neutrino mass hierarchy. With a dense array of optical modules it will be
possible to determine the inelasticity, , of the charged current
events in addition to the neutrino energy and the muon zenith angle
. The discovery potential of the detectors will substantially
increase with the measurement of . It will enable (i) a partial separation
of the neutrino and antineutrino signals; (ii) a better reconstruction of the
neutrino direction; (iii) the reduction of the neutrino parameters degeneracy;
(iv) a better control of systematic uncertainties; (v) a better identification
of the events. It will improve the sensitivity to the CP-violation
phase. The three dimensional, , oscillograms
with the kinematical as well as the experimental smearing are computed. We
present the asymmetry distributions in the plane for
different intervals of and study their properties. We show that the
inelasticity information reduces the effect of degeneracy of parameters by 30%.
With the inelasticity, the total significance of establishing mass hierarchy
may increase by 20% - 50%, thus effectively increasing the volume of the
detector by factor 1.5 - 2.Comment: 19 pages, 10 figure
Algebraic Renormalization of Supersymmetric Yang-Mills Chern-Simons Theory in the Wess-Zumino Gauge
We consider a N=2 supersymmetric Yang-Mills-Chern-Simons model, coupled to
matter, in the Wess-Zumino gauge. The theory is characterized by a superalgebra
which displays two kinds of obstructions to the closure on the translations:
field dependent gauge transformations, which give rise to an infinite algebra,
and equations of motion. The aim is to put the formalism in a closed form,
off-shell, without introducing auxiliary fields. In order to perform that, we
collect all the symmetries of the model into a unique nilpotent Slavnov-Taylor
operator. Furthermore, we prove the renormalizability of the model through the
analysis of the cohomology arising from the generalized Slavnov-Taylor
operator. In particular, we show that the model is free of anomaly.Comment: 17 pages, latex, no figures. Computation of the cohomology corrected.
Appendix adde
Quantum key distribution over 30km of standard fiber using energy-time entangled photon pairs: a comparison of two chromatic dispersion reduction methods
We present a full implementation of a quantum key distribution system using
energy-time entangled photon pairs and functioning with a 30km standard telecom
fiber quantum channel. Two bases of two orthogonal states are implemented and
the setup is quite robust to environmental constraints such as temperature
variation. Two different ways to manage chromatic dispersion in the quantum
channel are discussed.Comment: 10 pages, 4 figure
Photon counting for quantum key distribution with Peltier cooled InGaAs/InP APD's
The performance of three types of InGaAs/InP avalanche photodiodes is
investigated for photon counting at 1550 nm in the temperature range of
thermoelectric cooling. The best one yields a dark count probability of per gate (2.4 ns) at a detection efficiency of 10% and a
temperature of -60C. The afterpulse probability and the timing jitter are also
studied. The results obtained are compared with those of other papers and
applied to the simulation of a quantum key distribution system. An error rate
of 10% would be obtained after 54 kilometers.Comment: 8 pages, 10 figures, submitted to Journal of Modern Optic
Enhanced Autocompensating Quantum Cryptography System
We have improved the hardware and software of our autocompensating system for
quantum key distribution by replacing bulk optical components at the end
stations with fiber-optic equivalents and implementing software that
synchronizes end-station activities, communicates basis choices, corrects
errors and performs privacy amplification over a local area network. The all
fiber-optic arrangement provides stable, efficient and high-contrast routing of
the photons. The low bit error rate leads to high error correction efficiency
and minimizes data sacrifice during privacy amplification. Characterization
measurements made on a number of commercial avalanche photodiodes are presented
that highlight the need for improved devices tailored specifically for quantum
information applications. A scheme for frequency shifting the photons returning
from Alice's station to allow them to be distinguished from backscattered noise
photons is also described.
OCIS codes: 030.5260, 060.0060, 060.2360, 230.2240, 270.5570.Comment: 13 pages, 1 table, 9 figures; Applied Optics LP (in press, to appear
3/02
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