Search results for "Tropa"
showing 10 items of 170 documents
Large-scale Cosmic-Ray Anisotropies above 4 EeV Measured by the Pierre Auger Observatory
2018
We present a detailed study of the large-scale anisotropies of cosmic rays with energies above 4 EeV measured using the Pierre Auger Observatory. For the energy bins [4,8] EeV and $E\geq 8$ EeV, the most significant signal is a dipolar modulation in right ascension at energies above 8 EeV, as previously reported. In this paper we further scrutinize the highest-energy bin by splitting it into three energy ranges. We find that the amplitude of the dipole increases with energy above 4 EeV. The growth can be fitted with a power law with index $\beta=0.79\pm 0.19$. The directions of the dipoles are consistent with an extragalactic origin of these anisotropies at all the energies considered. Addi…
RESULTS FROM AMANDA
2002
The Antarctic Muon and Neutrino Detector Array (AMANDA) is a high-energy neutrino telescope operating at the geographic South Pole. It is a lattice of photo-multiplier tubes buried deep in the polar ice. The primary goal of this detector is to discover astrophysical sources of high energy neutrinos. We describe the detector methods of operation and present results from the AMANDA-B10 prototype. We demonstrate the improved sensitivity of the current AMANDA-II detector. We conclude with an outlook to the envisioned sensitivity of the future IceCube detector.
Limits on the muon flux from neutralino annihilations at the center of the Earth with AMANDA
2006
A search has been performed for nearly vertically upgoing neutrino-induced muons with the Antarctic Muon And Neutrino Detector Array (AMANDA), using data taken over the three year period 1997–99. No excess above the expected atmospheric neutrino background has been found. Upper limits at 90% confidence level have been set on the annihilation rate of neutralinos at the center of the Earth, as well as on the muon flux at AMANDA induced by neutrinos created by the annihilation products.
Measurement of the cosmic ray composition at the knee with the SPASE-2/AMANDA-B10 detectors
2004
The mass composition of high-energy cosmic rays at energies above 1015 eV can provide crucial information for the understanding of their origin. Air showers were measured simultaneously with the SPASE-2 air shower array and the AMANDA-B10 Cherenkov telescope at the South Pole. This combination has the advantage to sample almost all high-energy shower muons and is thus a new approach to the determination of the cosmic ray composition. The change in the cosmic ray mass composition was measured versus existing data from direct measurements at low energies. Our data show an increase of the mean log atomic mass 〈lnA〉 by about 0.8 between 500 TeV and 5 PeV. This trend of an increasing mass throug…
Multimessenger Astronomy with Neutrinos
2021
Multimessenger astronomy is arguably the branch of the astroparticle physics field that has seen the most significant developments in recent years. In this manuscript, we will review the state-of-the-art, the recent observations, and the prospects and challenges for the near future. We will give special emphasis to the observation carried out with neutrino telescopes.
Evidence that Ultra-High-Energy Gamma Rays are a Universal Feature Near Powerful Pulsars
2021
The highest-energy known gamma-ray sources are all located within 0.5 degrees of extremely powerful pulsars. This raises the question of whether ultra-high-energy (UHE; $>$ 56 TeV) gamma-ray emission is a universal feature expected near pulsars with a high spin-down power. Using four years of data from the High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory, we present a joint-likelihood analysis of ten extremely powerful pulsars to search for UHE gamma-ray emission correlated with these locations. We report a significant detection ($>$ 3$��$), indicating that UHE gamma-ray emission is a generic feature of powerful pulsars. We discuss the emission mechanisms of the gamma rays a…
Limits on the high-energy gamma and neutrino fluxes from the SGR 1806-20 giant flare of 27 December 2004 with the AMANDA-II detector.
2006
On December 27th 2004, a giant gamma flare from the Soft Gamma-ray Repeater 1806-20 saturated many satellite gamma-ray detectors. This event was by more than two orders of magnitude the brightest cosmic transient ever observed. If the gamma emission extends up to TeV energies with a hard power law energy spectrum, photo-produced muons could be observed in surface and underground arrays. Moreover, high-energy neutrinos could have been produced during the SGR giant flare if there were substantial baryonic outflow from the magnetar. These high-energy neutrinos would have also produced muons in an underground array. AMANDA-II was used to search for downgoing muons indicative of high-energy gamm…
Five years of searches for point sources of astrophysical neutrinos with the AMANDA-II neutrino telescope
2007
We report the results of a five-year survey of the northern sky to search for point sources of high energy neutrinos. The search was performed on the data collected with the AMANDA-II neutrino telescope in the years 2000 to 2004, with a live-time of 1001 days. The sample of selected events consists of 4282 upward going muon tracks with high reconstruction quality and an energy larger than about 100 GeV. We found no indication of point sources of neutrinos and set 90% confidence level flux upper limits for an all-sky search and also for a catalog of 32 selected sources. For the all-sky search, our average (over declination and right ascension) experimentally observed upper limit \Phi^{0}=(E/…
Theory and implications of neutrino mass
1989
Abstract I briefly review the basic theory of neutrino mass from the point of view of modern gauge theories. Some of the implications of neutrino masses for particle physics, nuclear physics, cosmology and astrophysics are discussed.
Multiyear search for a diffuse flux of muon neutrinos with AMANDA-II
2007
A search for TeV - PeV muon neutrinos from unresolved sources was performed on AMANDA-II data collected between 2000 and 2003 with an equivalent livetime of 807 days. This diffuse analysis sought to find an extraterrestrial neutrino flux from sources with non-thermal components. The signal is expected to have a harder spectrum than the atmospheric muon and neutrino backgrounds. Since no excess of events was seen in the data over the expected background, an upper limit of E^{2}\Phi_{90% C.L.} < 7.4 x 10^{-8} GeV cm^{-2} s^{-1} sr^{-1} is placed on the diffuse flux of muon neutrinos with a \Phi \propto E^{-2} spectrum in the energy range 16 TeV to 2.5 PeV. This is currently the most sensitive…