Search results for " neutrino"
showing 10 items of 727 documents
Deep-Sea Bioluminescence Blooms after Dense Water Formation at the Ocean Surface
2013
The deep ocean is the largest and least known ecosystem on Earth. It hosts numerous pelagic organisms, most of which are able to emit light. Here we present a unique data set consisting of a 2.5-year long record of light emission by deep-sea pelagic organisms, measured from December 2007 to June 2010 at the ANTARES underwater neutrino telescope in the deep NW Mediterranean Sea, jointly with synchronous hydrological records. This is the longest continuous time-series of deep-sea bioluminescence ever recorded. Our record reveals several weeks long, seasonal bioluminescence blooms with light intensity up to two orders of magnitude higher than background values, which correlate to changes in th…
Time calibration and search for cosmic sources of high energy neutrinos with the ANTARES neutrino telescope
2013
210 páginas. Tesis Doctoral del Departamento de Física Atómica, Molecular y Nuclear de la Universidad de Valencia y del Instituto de Física Corpuscular (IFIC).
Limit on the diffuse flux of ultrahigh energy tau neutrinos with the surface detector of the Pierre Auger Observatory
2009
Data collected at the Pierre Auger Observatory are used to establish an upper limit on the diffuse flux of tau neutrinos in the cosmic radiation. Earth-skimming ντ may interact in the Earth's crust and produce a τ lepton by means of charged-current interactions. The τ lepton may emerge from the Earth and decay in the atmosphere to produce a nearly horizontal shower with a typical signature, a persistent electromagnetic component even at very large atmospheric depths. The search procedure to select events induced by τ decays against the background of normal showers induced by cosmic rays is described. The method used to compute the exposure for a detector continuously growing with time is de…
On the selection of AGN neutrino source candidates for a source stacking analysis with neutrino telescopes
2006
The sensitivity of a search for sources of TeV neutrinos can be improved by grouping potential sources together into generic classes in a procedure that is known as source stacking. In this paper, we define catalogs of Active Galactic Nuclei (AGN) and use them to perform a source stacking analysis. The grouping of AGN into classes is done in two steps: first, AGN classes are defined, then, sources to be stacked are selected assuming that a potential neutrino flux is linearly correlated with the photon luminosity in a certain energy band (radio, IR, optical, keV, GeV, TeV). Lacking any secure detailed knowledge on neutrino production in AGN, this correlation is motivated by hadronic AGN mode…
The IceCube data acquisition system: Signal capture, digitization, and timestamping
2008
IceCube is a km-scale neutrino observatory under construction at the South Pole with sensors both in the deep ice (InIce) and on the surface (IceTop). The sensors, called Digital Optical Modules (DOMs), detect, digitize and timestamp the signals from optical Cherenkov-radiation photons. The DOM Main Board (MB) data acquisition subsystem is connected to the central DAQ in the IceCube Laboratory (ICL) by a single twisted copper wire-pair and transmits packetized data on demand. Time calibration is maintained throughout the array by regular transmission to the DOMs of precisely timed analog signals, synchronized to a central GPS-disciplined clock. The design goals and consequent features, func…
Search for Extraterrestrial Point Sources of Neutrinos with AMANDA-II
2003
We present the results of a search for point sources of high energy neutrinos in the northern hemisphere using AMANDA-II data collected in the year 2000. Included are flux limits on several AGN blazars, microquasars, magnetars and other candidate neutrino sources. A search for excesses above a random background of cosmic-ray-induced atmospheric neutrinos and misreconstructed downgoing cosmic-ray muons reveals no statistically significant neutrino point sources. We show that AMANDA-II has achieved the sensitivity required to probe known TeV gamma-ray sources such as the blazar Markarian 501 in its 1997 flaring state at a level where neutrino and gamma-ray fluxes are equal.
Search for high energy cosmic muon neutrinos from variable gamma-ray sources and time calibration of the optical modules of the ANTARES telescope
2015
325 páginas. Tesis Doctoral del Departamento de Física Atómica, Molecular y Nuclear de la Universidad de Valencia y del Instituto de Física Corpuscular (IFIC).
Search for neutrino emission from gamma-ray flaring blazars with the ANTARES telescope
2012
The ANTARES telescope observes a full hemisphere of the sky all the time with a duty cycle close to 100%. This makes it well suited for an extensive observation of neutrinos produced in astrophysical transient sources. In the surrounding medium of blazars, i.e. active galactic nuclei with their jets pointing almost directly towards the observer, neutrinos may be produced together with gamma-rays by hadronic interactions, so a strong correlation between neutrinos and gamma-rays emissions is expected. The time variability information of the studied source can be obtained by the gamma-ray light curves measured by the LAT instrument on-board the Fermi satellite. If the expected neutrino flux ob…
Measurement of acoustic attenuation in South Pole ice
2010
Using the South Pole Acoustic Test Setup (SPATS) and a retrievable transmitter deployed in holes drilled for the IceCube experiment, we have measured the attenuation of acoustic signals by South Pole ice at depths between 190 m and 500 m. Three data sets, using different acoustic sources, have been analyzed and give consistent results. The method with the smallest systematic uncertainties yields an amplitude attenuation coefficient alpha = 3.20 \pm 0.57 km^(-1) between 10 and 30 kHz, considerably larger than previous theoretical estimates. Expressed as an attenuation length, the analyses give a consistent result for lambda = 1/alpha of ~1/300 m with 20% uncertainty. No significant depth or …
Neutrino pair annihilation near accreting, stellar-mass black holes
2006
We investigate the energy-momentum deposition due to neutrino-antineutrino annihilation in the vicinity of axisymmetric, accreting black holes (BHs) by numerically ray-tracing neutrino trajectories in a Kerr space-time. Hyperaccreting stellar-mass BHs are widely considered as energy sources that can drive ultrarelativistic outflows with the potential to produce gamma-ray bursts. In contrast to earlier works, we provide an extensive and detailed parameter study of the influence of general relativistic (GR) effects and of different neutrinosphere geometries. These include idealized thin disks, tori, and spheres, or are constructed as non-selfgravitating equilibrium matter distributions for va…