| 11. |
- Ahrens, J., et al.
(författare)
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Observation of high energy atmospheric neutrinos with the Antarctic muon and neutrino detector array
- 2002
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Ingår i: Physical Review D. - : American Physical Society. - 1550-7998 .- 1550-2368. ; 66:1, s. 120051-1200520
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Tidskriftsartikel (refereegranskat)abstract
- The Antarctic muon and neutrino detector array (AMANDA) began collecting data with ten strings in 1997. Results from the first year of operation are presented. Neutrinos coming through the Earth from the Northern Hemisphere are identified by secondary muons moving upward through the array. Cosmic rays in the atmosphere generate a background of downward moving muons, which are about 106 times more abundant than the upward moving muons. Over 130 days of exposure, we observed a total of about 300 neutrino events. In the same period, a background of 1.05 × 109 cosmic ray muon events was recorded. The observed neutrino flux is consistent with atmospheric neutrino predictions. Monte Carlo simulations indicate that 90% of these events lie in the energy range 66 GeV to 3.4 TeV. The observation of atmospheric neutrinos consistent with expectations establishes AMANDA-B10 as a working neutrino telescope.
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| 12. |
- Ahrens, J., et al.
(författare)
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Results from the AMANDA telescope
- 2003
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Ingår i: Nuclear Physics A. - : Elsevier. - 0375-9474 .- 1873-1554. ; 721, s. C545-C548
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Tidskriftsartikel (refereegranskat)abstract
- We present results from the AMANDA high energy neutrino telescope located at the South Pole. They include measurements of the atmospheric neutrino flux, search for UHE point sources, and diffuse sources producing electromagnetic/hadronic showers at the detector or close to it.
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| 13. |
- Ahrens, J., et al.
(författare)
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Search for Extraterrestrial Point Sources of Neutrinos with AMANDA-II
- 2004
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 92:7, s. 711021-711025
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Tidskriftsartikel (refereegranskat)abstract
- The results of a search for point sources of high energy neutrinos in the northern hemisphere were presented using AMANDA-II data collected in the year 2000. The results included the flux limits on several active-galactic-nuclei 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-rays muons, which revealed no statistically significant neutrino point sources was also presented. It was shown that AMANDA-II had achieved the sensitivity required to probe known TeV γ-ray sources such as the blazar Markarian 501 in its 1997 flaring state at a level where neutrino and γ-ray fluxes were equal.
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| 14. |
- Ahrens, J., et al.
(författare)
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Search for supernova neutrino bursts with the AMANDA detector
- 2001
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Ingår i: Astroparticle physics. - : Elsevier. - 0927-6505 .- 1873-2852. ; 16:4, s. 345-359
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Tidskriftsartikel (refereegranskat)abstract
- The core collapse of a massive star in the Milky Way will produce a neutrino burst, intense enough to be detected by existing underground detectors. The AMANDA neutrino telescope located deep in the South Pole ice can detect MeV neutrinos by a collective rate increase in all photo-multipliers on top of dark noise. The main source of light comes from positrons produced in the CC reaction of anti-electron neutrinos on free protons ve + p → e+ + n. This paper describes the first supernova search performed on the full sets of data taken during 1997 and 1998 (215 days of live time) with 302 of the detector's optical modules. No candidate events resulted from this search. The performance of the detector is calculated, yielding a 70% coverage of the galaxy with one background fake per year with 90% efficiency for the detector configuration under study. An upper limit at the 90% c.l. on the rate of stellar collapses in the Milky Way is derived, yielding 4.3 events per year. A trigger algorithm is presented and its performance estimated. Possible improvements of the detector hardware are reviewed.
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| 15. |
- Ambrosio, M, et al.
(författare)
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Final results of magnetic monopole searches with the MACRO experiment
- 2002
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Ingår i: European Physical Journal C. - : Springer. - 1434-6044 .- 1434-6052. ; 25:4, s. 511-522
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Tidskriftsartikel (refereegranskat)abstract
- We present the final results obtained by the MACRO experiment in the search for GUT magnetic monopoles in the penetrating cosmic radiation, for the range 4 x 10(-5) < 3 < 1. Several searches with all the MACRO sub-detectors (i.e. scintillation counters, limited streamer tubes and nuclear track detectors) were performed, both in stand alone and combined ways. No candidates were detected and a 90% Confidence Level (C.L.) upper limit to the local magnetic monopole flux was set at the level of 1.4 x 10(-16) cm(-2) s(-1) sr(-1). This result is the first experimental limit obtained in direct searches which is well below the Parker bound in the whole 3 range in which GUT magnetic monopoles are,expected.
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| 16. |
- Ambrosio, M, et al.
(författare)
-
Matter effects in upward-going muons and sterile neutrino oscillations
- 2001
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Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 517:1-2, s. 59-66
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Tidskriftsartikel (refereegranskat)abstract
- The angular distribution of upward-going muons produced by atmospheric neutrinos in the rock below the MACRO detector shows anomalies in good agreement with two flavor nu (mu) --> nu (tau) oscillations with maximum mixing and Deltam(2) around 0.0024 eV(2). Exploiting the dependence of magnitude of the matter effect on oscillation channel, and using a set of 809 upward-going muons observed in MACRO, we show that the two flavor nu (mu) --> nu (s) oscillation is disfavored with 99% C.L. with respect to nu (mu) --> nu (tau). (C) 2001 Elsevier Science B.V. All rights reserved.
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| 17. |
- Ambrosio, M, et al.
(författare)
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Measurements of atmospheric muon neutrino oscillations, global analysis of the data collected with MACRO detector
- 2004
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Ingår i: European Physical Journal C. - : Springer. - 1434-6044 .- 1434-6052. ; 36:3, s. 323-339
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Tidskriftsartikel (refereegranskat)abstract
- The final analysis of atmospheric neutrino events collected with the MACRO detector is presented. Three different classes of events, generated by neutrinos in different energy ranges, are studied looking at rates, angular distributions and estimated energies. The results are consistent for all the subsamples and indicate a flux deficit that depends on energy and path - length of neutrinos. The no - oscillation hypothesis is excluded at similar to 5sigma, while the hypothesis of nu(mu) --> nu(tau) oscillation gives a satisfactory description of all data. The parameters with highest probability in a two flavor scenario are sin(2) 2theta(m) = 1 and Deltam(2) = 0.0023 eV(2). This result is independent of the absolute normalization of the atmospheric neutrino fluxes. The data can also be used to put experimental constrain on this normalization.
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| 18. |
- Ambrosio, M, et al.
(författare)
-
Search for nucleon decays induced by GUT magnetic monopoles with the MACRO experiment
- 2002
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Ingår i: European Physical Journal C. - : Springer. - 1434-6044 .- 1434-6052. ; 26:2, s. 163-172
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Tidskriftsartikel (refereegranskat)abstract
- The interaction of a Grand Unification Magnetic Monopole with a nucleon can lead to a barion-number violating process in which the nucleon decays into a lepton and one or more mesons (catalysis of nucleon decay). In this paper we report an experimental study of the effects of a catalysis process in the MACRO detector. Using a dedicated analysis we obtain new magnetic monopole (MM) flux upper limits at the level of similar to 3 (.) 10(-16) cm(-2) s(-1) sr(-1) for 1.1(.) 10(-4) less than or equal to \beta\ less than or equal to 5 (.) 10(-3), based on the search for catalysis events in the MACRO data. We also analyze the dependence of the MM flux limit on the catalysis cross section.
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| 19. |
- Andrés, E., et al.
(författare)
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Observation of high-energy neutrinos using Čerenkov detectors embedded deep in Antarctic ice
- 2001
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 410:6827, s. 441-443
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Tidskriftsartikel (refereegranskat)abstract
- Neutrinos are elementary particles that carry no electric charge and have little mass. As they interact only weakly with other particles, they can penetrate enormous amounts of matter, and therefore have the potential to directly convey astrophysical information from the edge of the Universe and from deep inside the most cataclysmic high-energy regions. The neutrino's great penetrating power, however, also makes this particle difficult to detect. Underground detectors have observed low-energy neutrinos from the Sun and a nearby supernova2, as well as neutrinos generated in the Earth's atmosphere. But the very low fluxes of high-energy neutrinos from cosmic sources can be observed only by much larger, expandable detectors in, for example, deep water3,4 or ice5. Here we report the detection of upwardly propagating atmospheric neutrinos by the ice-based Antarctic muon and neutrino detector array (AMANDA). These results establish a technology with which to build a kilometre-scale neutrino observatory necessary for astrophysical observations1.
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| 20. |
- Andrés, E., et al.
(författare)
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Recent results from AMANDA
- 2001
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Ingår i: International Journal of Modern Physics A. - 0217-751X .- 1793-656X. ; 16:1C, s. 1013-1015
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Tidskriftsartikel (refereegranskat)abstract
- We present results based on data taken in 1997 with the 302-PMT Antarctic Muon and Neutrino Detector Array-B10 ("AMANDA-B10") array. Atmospheric neutrinos created in the northern hemisphere are observed indirectly through their charged current interactions which produce relativistic, Cherenkov-light-emitting upgoing muons in the South Pole ice cap. The reconstructed angular distribution of these events is in good agreement with expectation and demonstrates the viability of this ice-based device as a neutrino telescope.
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