Search results for "methods [Diffusion Tensor Imaging]"
showing 10 items of 992 documents
Muon energy reconstruction in ANTARES and its application to the diffuse neutrino flux
2003
The European collaboration ANTARES aims to operate a large neutrino telescope in the Mediterranean Sea, 2400 m deep, 40 km from Toulon (France). Muon neutrinos are detected through the muon produced in charged current interactions in the medium surrounding the detector. The Cherenkov light emitted by the muon is registered by a 3D photomultiplier array. Muon energy can be inferred using 3 different methods based on the knowledge of the features of muon energy losses.They result in an energy resolution of a factor \~ 2 above 1 TeV. The ANTARES sensitivity to diffuse neutrino flux models is obtained from an energy cut, rejecting most of the atmospheric neutrino background which has a softer s…
Cancelling out systematic uncertainties
2011
We present a method to minimize, or even cancel out, the nuisance parameters affecting a measurement. Our approach is general and can be applied to any experiment or observation. We compare it with the bayesian technique used to deal with nuisance parameters: marginalization, and show how the method compares and improves by avoiding biases. We illustrate the method with several examples taken from the astrophysics and cosmology world: baryonic acoustic oscillations, cosmic clocks, Supernova Type Ia luminosity distance, neutrino oscillations and dark matter detection. By applying the method we recover some known results but also find some interesting new ones. For baryonic acoustic oscillati…
Looking for Axion Dark Matter in Dwarf Spheroidals
2018
We study the extent to which the decay of cold dark matter axions can be probed with forthcoming radio telescopes such as the Square Kilometer Array (SKA). In particular we focus on signals arising from dwarf spheroidal galaxies, where astrophysical uncertainties are reduced and the expected magnetic field strengths are such that signals arising from axion decay may dominate over axion-photon conversion in a magnetic field. We show that with $\sim100$ hours of observing time, SKA could improve current sensitivity by a factor of about five.
Tau Appearance from High-Energy Neutrino Interactions
2022
High-energy muon- and electron-neutrinos yield a non-negligible flux of tau neutrinos as they propagate through Earth. In this letter, we address the impact of this additional component in the PeV and EeV energy regimes for the first time. This contribution is predicted to be significantly larger than the atmospheric background above 300 TeV, and alters current and future neutrino telescopes' capabilities to discover a cosmic tau-neutrino flux. Further we demonstrate that Earthskimming neutrino experiments, designed to observe tau neutrinos, will be sensitive to cosmogenic neutrinos even in extreme scenarios without a primary tau-neutrino component.
Ultrahigh-energy neutrino flux as a probe of large extra dimensions
2007
A suppression in the spectrum of ultrahigh-energy (UHE, >= 10^{18} eV) neutrinos will be present in extra-dimensional scenarios, due to enhanced neutrino-antineutrino annihilation processes with the supernova relic neutrinos. In the n>4 scenario, being n the number of extra dimensions, neutrinos can not be responsible for the highest energy events observed in the UHE cosmic ray spectrum. A direct implication of these extra-dimensional interactions would be the absence of UHE neutrinos in ongoing and future neutrino telescopes.
Foreground Contributions to 0.2-2 Degree CMB Anisotropies
1994
We examine the extent to which galactic and extragalactic foregrounds can hamper the detection of primordial Cosmic Microwave Background (CMB) anisotropies. We limit our discussion to intermediate angular scales, $10^{\prime}\lsim \theta \lsim 2^{\circ}$, since many current as well as future experiments have been designed to map CMB anisotropies at these angular scales. In fact, scales of $\gsim 10^{\prime}$ are of crucial importance to test both the conditions in the early Universe and current theories of the gravitational collapse.
Coincidence of a high-fluence blazar outburst with a PeV-energy neutrino event
2016
The discovery of extraterrestrial very-high-energy neutrinos by the IceCube collaboration has launched a quest for the identification of their astrophysical sources. Gamma-ray blazars have been predicted to yield a cumulative neutrino signal exceeding the atmospheric background above energies of 100 TeV, assuming that both the neutrinos and the gamma-ray photons are produced by accelerated protons in relativistic jets. Since the background spectrum falls steeply with increasing energy, the individual events with the clearest signature of being of an extraterrestrial origin are those at PeV energies. Inside the large positional-uncertainty fields of the first two PeV neutrinos detected by Ic…
Highlights from the ARGO-YBJ Experiment
2012
""The ARGO-YBJ experiment at YangBaJing in Tibet (4300m a.s.l.) has been taking data with its full layout since October 2007. Here we present a few significant results obtained in gamma-ray astronomy and cosmic-ray physics. Emphasis is placed on the analysis of gamma-ray emission from point-like sources (Crab Nebula, MRK 421), on the preliminary limit on the antiproton\\\/proton flux ratio, on the large-scale cosmic-ray anisotropy and on the proton-air cross-section. The performance of the detector is also discussed, and the perspectives of the experiment are outlined.""
Astrophysik contra Astronomie
1981
[Astrophysics contra astronomy] means the displacement of astrometry and stellar astronomy as the main and solely conceded branches of astronomy by the new astrophysics. This displacement started with the introduction of spectroscopic and photometric methods of observation in astronomy founded by J. C. F. Zoellner and W. Huggins in the late 1850s. It was Zoellner, too, who gave the methodical and intrumental foundations of the new branch called consciously [Astrophysik] by him, because it gives insight into the [physical constitution] of the celestial bodies - whereas the traditional astronomy (or: astrophysics according to the older meaning) had been studying only the motions of the stars …
EMMA - A New Underground Cosmic-Ray Experiment
2005
A new type of cosmic-ray experiment is under construction in the Pyh\"asalmi mine in the underground laboratory of the University of Oulu, Finland. It aims to study the composition of cosmic rays at and above the knee region. The experiment, called EMMA, will cover approximately 150 square-metres of detector area. The array is capable of measuring the multiplicity and the lateral distribution of underground muons, and the arrival direction of the air shower. The full-size detector is expected to run by the end of 2007.